November 2014: Nice Seanonal Thanksgiving Ahead

[jasons2k]

Bring it.

[Andrew]

Current Hi-res models on this evening's rain chances. Looks like some streamer shows could continue across the area as a weak warm front/ washed out boundary progresses north. All times are at 00z or 6pm.


HRRR:

1ref_t5sfc_f11.png

Tx-Tech WRF:

dom_2km_sfc_dbz_f18.gif

NAM 4k:

rad12.gif

[srainhoutx]

Morning briefing from Jeff:

***Severe thunderstorms including tornadoes increasingly likely this Saturday.***

Powerful upper level storm system off the NW US coast currently will move rapidly SE and into W TX by early Saturday and sweep across the state late Saturday.

Moisture return clearly underway this morning with scattered showers developing in the corridor from Matagorda Bay to near I-10 west of Houston. Expect this activity to increase in coverage today and spread inland as a warm front moves toward the upper TX coast. Warm front will move inland tonight and progress across SE TX on Friday with additional scattered showers and a few thunderstorms especially along and north of the boundary. Warm sector air mass south of the boundary will support mid to upper 60 degree dewpoint maritime tropical air mass moving onshore. A few showers will be possible in the increasing onshore flow south of the warm front. Temperatures will be running about 20-30 degrees warmer than the first part of this week tomorrow and Saturday.

Saturday:
Powerful storm system sweeps across TX with impressively deep short wave rotating far south across S TX Saturday afternoon in the base of the upper level trough. Trough axis takes on a slight negative tilt pattern (SE to NW) which supports an overall increase in directional wind shear along the eastern flank of the trough axis (or in the region over the coastal bend and SE TX). Forecast models have shown a slight tendency to slow to eastward progression of the storm system slightly over the last 24 hours which places the greatest weather threat/impacts in the afternoon and evening hours of Saturday. A 35-45kt low level jet develops off the western Gulf of Mexico late Friday evening and continues into Saturday with a 100kt mid level jet streak carving into the region from the SW Saturday afternoon. The result is significant low level wind shear and wind energy in the lowest several thousand feet of the atmosphere. Latest guidance suggests breaks in the cloud cover are possible Saturday morning and early afternoon over SC/SE TX helping to boast surface based energy values (CAPE) and resulting in an increasingly unstable warm sector air mass.

Usually in this part of the state the warm sector is capped off and we await the actual strong forcing from the upper level trough or the cold front to develop a line of strong to severe thunderstorms. Saturday appears to be a possible exception where the warm sector air mass is only weakly capped and this could allow for the development of discrete supercell thunderstorms prior to the arrival of the main forcing toward early evening. This is important due to the fact that warm sector discrete supercells tend to produce a majority of the tornadoes in such severe weather outbreaks.

Model guidance is trending to point toward some development of discrete cells by early Saturday afternoon with an enhanced tornado threat which would be certainly supported by the sheared low level air mass resulting in updraft rotation. An example of the potential wind shear in the lowest part of the atmosphere being forecasted at noon on Saturday for IAH is a helicity value of around 260 m^2/s^2 on the GFS forecast sounding. Additionally the GFS shows a significant increase in PWS values between 06Z Saturday and 18Z Saturday from around 1.1 inches to nearly 1.70 inches.

The greatest severe weather threat currently appears across the southern 2/3rds of the area into the coastal bend and SC TX where the air mass becomes the most unstable Saturday afternoon and the favorable wind profiles and dynamics aloft align. (See SPC graphic outlines below).

The following threat analysis discusses the severe potential for Saturday:

Wind Damage:
Strong wind energy will be present both in the form of the low level jet overhead and mid level winds. Strong to severe thunderstorms will be capable of transporting some of this wind energy to the surface in the form of damaging winds of 60-70mph. This would be especially true in the event of an ESE or E moving squall line/MCS which guidance does develop out of C TX during the afternoon hours and sweeps across SE TX during the late afternoon and evening hours. The pattern supports bowing segments with the potential for larger than average corridors of wind damage.

Tornado:
The concern is in the potential for discrete warm sector development of supercells early Saturday afternoon in a favorable 850mb convergent zone over SC/SE TX. If supercells do in fact initiate in such a highly sheared and unstable air mass tornado formation is certainly possible. Such tornadoes would tend to be stronger than what we would normally see in this area and could track for a longer period of time on the ground. Cell motions would likely be quick toward the NE and ENE reducing warning lead times. This enhanced tornado threat is strongly conditional on the development of supercells in the warm sector air mass which as stated above is a bit unusual for this area. A lack of warm sector discrete cell development would reduce the tornado threat across the area.

In addition there would also be a tornado risk along the main squall line/MCS toward the early evening hours with what we more commonly see in this area which is weaker rain wrapped tornadoes along the leading edge of squall lines where localized vorticity values are increased.



Large Hail:
Colder mid level temperatures will arrive with the cold pocket of the upper level system. This would support a large hail threat with both warm sector supercells and with the squall line. This threat is secondary to the wind and tornado threat at the moment.

Heavy Rainfall:
A significant increase in moisture will occur tonight-early Saturday with scattered showers for the next 24-36 hours. Heavy rains will certainly occur with the strong to severe thunderstorms on Saturday, but fast storm motions should help negate a serious flood threat. Of some concern is the model tendency to slow the system some which could result in a slightly longer duration of the heavy rainfall threat and the potential for high precipitation supercells to train in the warm sector. The heavy rainfall threat is secondary to the wind and tornado threat at the moment.

SPC Day 3 (Saturday) Severe Weather Outlook:

[/i]

[Andrew]

12z gfs continues to show a decrease in speed of the shortwave across the western U.S. but shows better vertical alignment with the jet streaks. As Jeff mentioned in his email, highest Helicity and CAPE values exist SW of the Houston area where we could see some of the strongest storms. Another interesting component that could really interfere with forecasts is the continual support for a weak backdoor front. 12z gfs takes the front all the way to the I-45 corridor before WAA pushes moist air back in. By 00z tonight we should begin seeing a even better consensus as better sampling data is ingested into the models.

[SLM87TX]

If the storms have the best chance of going severe SW of Houston what will happen to them as they move farther northward do they keep a high tornadic chance or become Rain, Wind, and Hail maker? What should be expect north of I-10, as of now? Does the slowing of the shortwave increase flooding possibilities?

[tireman4]

I wonder if A&M ( I am sure Andrew can answer this) and UH will send up special balloons in wake of this ever present and continuing challenging weather period this Saturday?

[srainhoutx]

If the storms have the best chance of going severe SW of Houston what will happen to them as they move farther northward do they keep a high tornadic chance or become Rain, Wind, and Hail maker? What should be expect north of I-10, as of now? Does the slowing of the shortwave increase flooding possibilities?

HGX thinks the heavy rain threat is rather low compared to the severe storms with damaging winds and isolated tornado threat...

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1051 AM CST THU NOV 20 2014

TXZ163-164-176>179-195>200-210>214-226-227-235>238-211700-
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-
GALVESTON-GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-MADISON-MATAGORDA-
MONTGOMERY-POLK-SAN JACINTO-TRINITY-WALKER-WALLER-WASHINGTON-
WHARTON-
1051 AM CST THU NOV 20 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A STRONG STORM SYSTEM WILL APPROACH SOUTHEAST TEXAS ON SATURDAY
AFTERNOON. STRONG DYNAMICS AND FAVORABLE UPPER LEVEL WINDS SUPPORT
NUMEROUS SHOWERS AND THUNDERSTORMS DEVELOPING IN THE AFTERNOON
OVER THE WESTERN THIRD OF SOUTHEAST TEXAS AND OVERSPREADING THE
REST OF THE AREA DURING THE REMAINDER OF THE DAY. THE PRIMARY
SEVERE WEATHER HAZARD WILL BE STRONG DAMAGING WINDS AND ISOLATED
TORNADOES. THE SYSTEM SHOULD MOVE RELATIVELY QUICKLY SO EXCESSIVE
RAINFALL IS NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT...

EMERGENCY MANAGERS AND STORM SPOTTERS SHOULD PREPARE FOR POSSIBLE
INVOLVEMENT SATURDAY AFTERNOON EVENING.

[Andrew]

I wonder if A&M ( I am sure Andrew can answer this) and UH will send up special balloons in wake of this ever present and continuing challenging weather period this Saturday?

We already have plans to launch one tomorrow and then we will launch one Saturday no matter what if we see a moderate risk.

[tireman4]

Gotcha. Thanks for the quick response.

[unome]

hgx updated their weather briefing with a video this am

http://www.srh.noaa.gov/hgx/?n=brief_support

[srainhoutx]

The Updated Model Diagnostic Discussion indicated a slower, deeper (stronger) and further south tracking storm system is likely this Saturday...


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EST THU NOV 20 2014

VALID NOV 20/1200 UTC THRU NOV 24/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...STRONG SOUTHERN STREAM TROUGH LEADING TO WIDESPREAD RAIN FROM
THE PLAINS EASTWARD...

PREFERENCE: BLEND OF 12Z GFS/ECMWF
CONFIDENCE: AVERAGE

A DYNAMIC TROUGH OF SHORT TO MEDIUM WAVELENGTH WILL DIVE FROM
CALIFORNIA TOWARD THE RIO GRANDE BASIN. THE SYSTEM WILL CONTINUE
TO BE URGED ALONG TO THE EAST BY STRONG UPSTREAM FLOW...BUT THE
12Z MODELS TRENDED TOWARD A SLOWER PROGRESSION FROM LATE SATURDAY
INTO SUNDAY. THE MODELS THAT TRENDED SLOWER ARE ALSO A LITTLE
DEEPER AND FORECAST A TRACK THAT IS SUPPRESSED SOUTHWARD COMPARED
TO THE 00Z ECMWF. THESE TRENDS APPEAR REASONABLE FOR A STRONG AND
STILL DEEPENING WAVE...AND THE 12Z ECMWF SUPPORTED THE TREND. THE
NAM AND CANADIAN ARE GENERALLY CONSISTENT WITH THE GFS/ECMWF IN
THE MASS FIELDS...BUT THE NAM/CANADIAN PRECIPITATION OUTPUT IS
LESS PREFERRED. THE UKMET STRAYS FROM CONSENSUS ON DAY 3 WHEN IT
DRIVES THE CORE OF THE MID LEVEL WAVE STRONGLY EASTWARD INTO THE
DEEP SOUTH RATHER THAN LIFTING IT THROUGH THE MID MISSISSIPPI
VALLEY.

[srainhoutx]

While the 18Z NAM is still a bit too far out in time for an accurate analysis of the exact placement of the incoming storm, it does paint a disturbing situation with the further S and deeper storm suggested by all of the guidance and continues to advertise a negative tilted trough developing across S Central/SE Texas on Saturday.

The attachment 11202014 18Z NAM f60.gif is no longer available

[Andrew]

Updated spc:

"Forecast Discussion

SPC AC 210614

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1214 AM CST FRI NOV 21 2014

VALID 221200Z - 231200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF CNTRL TX AND
THE TX GULF COAST...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS
AND LOWER MS VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...LOWER MS VALLEY AND CNTRL GULF COAST...

...SUMMARY...
NUMEROUS STRONG TO SEVERE STORMS ARE EXPECTED TO DEVELOP FROM
CENTRAL TEXAS SOUTHEASTWARD TO THE TEXAS GULF COAST ON SATURDAY.
OTHER SEVERE STORMS ARE POSSIBLE FROM SOUTHERN LOUISIANA INTO
SOUTHERN MISSISSIPPI SATURDAY NIGHT. PRIMARY THREATS WILL BE
DAMAGING WIND AND A FEW TORNADOES...BUT LARGE HAIL WILL ALSO BE
POSSIBLE MAINLY OVER TEXAS.

...SRN PLAINS/LOWER MS VALLEY...
AN UPPER-LEVEL TROUGH WILL MOVE EWD ACROSS NRN MEXICO ON SATURDAY AS
A LOW-LEVEL JET REMAINS OVER SRN PLAINS. AT THE SFC...SOUTH TO
SOUTHEASTERLY FLOW ACROSS THE SRN PLAINS WILL MAINTAIN LOW-LEVEL
MOISTURE ACROSS MUCH OF CNTRL AND ERN TX WHERE DEWPOINTS ARE
FORECAST TO BE IN THE LOWER TO MID 60S F. ELEVATED THUNDERSTORMS MAY
BE ONGOING AT THE START OF THE PERIOD ON THE NOSE OF THE LOW-LEVEL
JET IN NORTH TX AND SRN OK. AS SFC TEMPS WARM DURING THE
DAY...SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED TO TAKE PLACE
SWD ACROSS THE TX HILL COUNTRY AND SEWD ONTO THE TX COASTAL PLAIN.
SEVERAL THUNDERSTORM CLUSTERS OR PERHAPS MCS DEVELOPMENT MAY OCCUR
DURING THE LATE AFTERNOON INTO THE EVENING.

MODEL FORECASTS SUGGEST THE GREATEST CHANCE FOR ORGANIZED CONVECTION
WILL BE JUST AHEAD OF THE UPPER-LEVEL TROUGH EARLY SATURDAY EVENING
FROM THE TX COASTAL PLAINS SEWD TO THE TX GULF COAST. FORECAST
SOUNDINGS AT SAN ANTONIO AND HOUSTON AT 00Z/SUN SHOW MLCAPE NEAR
1000 J/KG WITH 0-6 KM SHEAR OF 50 TO 60 KT. THIS ENVIRONMENT SHOULD
SUPPORT SUPERCELL DEVELOPMENT WITH STORMS THAT HAVE ACCESS TO
MAXIMIZED INSTABILITY. THE POTENTIAL FOR SUPERCELLS AND POSSIBLY A
TORNADO OR TWO MAY BE GREATEST ALONG THE MIDDLE TX COAST JUST AHEAD
OF A 60 TO 70 KT MID-LEVEL JET ROUNDING THE BASE OF THE TROUGH.
SUPERCELLS MAY ALSO PRODUCE ISOLATED LARGE HAIL. SOME MODELS SUGGEST
THAT A LINE OF STRONG TO SEVERE STORMS WILL DEVELOP IN CNTRL TX JUST
AHEAD OF THE APPROACHING UPPER-LEVEL TROUGH. IF THIS SCENARIO PANS
OUT...THEN A WIND DAMAGE THREAT WOULD DEVELOP LATE SATURDAY
AFTERNOON MOVING EWD FROM THE TX HILL COUNTRY TO THE VICTORIA AND
HOUSTON AREA WHERE A 30 PERCENT SEVERE PROBABILITY HAS BEEN
MAINTAINED.

...LOWER MS VALLEY...
AN UPPER-LEVEL TROUGH WILL MOVE FROM NRN MEXICO INTO THE RIO GRANDE
VALLEY ON SATURDAY. LOW-LEVEL MOISTURE ADVECTION AHEAD OF THE
APPROACHING SYSTEM SHOULD INCREASE SFC DEWPOINTS ACROSS THE LOWER MS
VALLEY INTO THE LOWER TO MID 60S F. A SUBTLE LEAD SHORTWAVE TROUGH
IN THE CNTRL GULF COAST STATES LATE SATURDAY AFTERNOON MAY PROVIDE
ENOUGH LARGE-SCALE ASCENT FOR ISOLATED TO SCATTERED THUNDERSTORM
DEVELOPMENT. MODERATE INSTABILITY NEAR THE COAST ALONG WITH ABOUT 50
KT OF DEEP-LAYER SHEAR EVIDENT ON FORECAST SOUNDINGS SHOULD BE
ENOUGH FOR A SEVERE THREAT FROM LATE SATURDAY AFTERNOON THROUGH
SATURDAY NIGHT. ALTHOUGH A TORNADO THREAT COULD DEVELOP WITH
ISOLATED ROTATING CELLS THAT MOVE ONSHORE...THE GREATER THREAT COULD
BE FOR WIND DAMAGE AS A LINE OF STRONG STORMS MOVES INTO THE REGION
FROM THE WEST SATURDAY NIGHT.

..BROYLES.. 11/21/2014"

[Katdaddy]

Our potent storm system which is likely to become negatively tilted across Central and S Central TX can be seen on IR satellite over SoCal this morning. Temps in the low to mid 60s currently as GOM moisture continues to stream inland. A few areas of light to moderate rain moving across SE TX this morning. A significant severe weather event on target to unfold across a large portion of TX tomorrow afternoon. The SPC continues the Enhanced Risk across Central, S Central and SE TX. The environment will support supercell development to the SW of Houston across the Middle TX Coast including the Victoria area leading to a tornado threat. These storms will likely consolidate into MCS later in the afternoon and evening resulting in possible widespread damaging winds across SE TX and the Upper TX Coast.

[SLM87TX]

The atmosphere sure seems to be getting saturated. Will these trainer shower stay around all day or will they die down and open up the atmosphere?

[srainhoutx]

I'm not seeing anything that raises a big flag that changes the overall thinking regarding tomorrow. The warm front has moved well to the N of Central and SE Texas and as the upper low over Southern California begins its trek ESE across N Mexico and nears W Texas, rapid cyclogenesis should commence and a potent surface low will likely develop. If I recall correctly back in November 1992, we had a few early day storms and cloudiness before all heck broke loose and low topped rain wrapped tornado reports began coming in. The severe analogs for our cool season severe weather episodes are still showing up, so I encourage folks to not let their guard down tomorrow and into Sunday for our neighbors in Louisiana and Mississippi. After an extended cold snap, the last thing on many folks mind is a severe weather episode.

[srainhoutx]

Morning briefing from Jeff:

***Severe Weather Outbreak likely Saturday afternoon and evening***

Warm air advection regime in place this morning with scattered showers and even a few pockets of heavy rain across the area. This will continue into the afternoon hours and then shift north and west with the core axis of the low level jet. Expect a fairly inactive overnight period. Main focus continues to be on Saturday which is covered from this point on.

Saturday:
Powerful upper level storm system currently over southern CA will move ESE today and tonight and sweep across TX on Saturday. Ingredients will come together to produce at least a couple of rounds of potentially severe thunderstorms Saturday afternoon and evening. Upper level system will move directly over SC TX Saturday evening taking on a slight SE to NW tilt (this indicates the trough axis is tilting negative compared to most of the time when they are positive or SW to NE). This tilt allows the cold pocket aloft associated with the storm system to overrun the warm sector ahead of the system to the SE allowing that warm sector air mass to become very unstable (cold air over warm air is unstable in the atmosphere). Additionally, very strong jet stream dynamics will come to bear across the region with 250mb high level winds splitting apart from the coastal bend through NE TX which allows general overall rising air motions. A 40kt low level jet will be in place from the coastal bend to NC TX which will be overtopped by a 100kt mid level jet streak out of the WSW. Wind profiles show strong low level veering of the wind field over the coastal bend and SE TX with 0-6km shear values of 60-70kts and 0-1km helicity values of 200-400 m^2/s^2. This all points to a lot of wind energy and certainly the potential for thunderstorm updrafts to rotate (turn with height). While the shear is there the instability is still lacking some. Forecasted CAPE values are in the 700-1200 J/kg range for Saturday afternoon which is not much surface based energy. The main reason for the lack of instability is the expected widespread cloud cover and showers/thunderstorms across the warm sector. The spreading of the cold pocket aloft could help increase these values some along with any breaks in the overcast. With that said, past historic severe weather outbreaks in November have not required significant amounts of CAPE and the forecasted energy values on Saturday fall very close in line with past analog outbreaks which produced both severe weather and tornadoes, so while I would like to see better values (say around 1500) what we currently are seeing forecasted can get the job done.

Main threats will be wind damage and isolated to possibly scattered tornadoes.

Tornado:
Tornado threat remains conditional on favorable shear and instability to align and this looks possible early Saturday afternoon along a SE to NW orientated boundary from Matagorda Bay to Austin. TTU 3km WRF has shown this setup in the last few model runs of severe storms (some supercells) developing on this boundary and lifting NE across SE TX Saturday afternoon. This boundary appears to be the maritime front separating the truly tropical air to the SW over the western Gulf from the more modified tropical air mass in place over the region currently. Low level winds will likely be backed some along this boundary and this supports an increased tornado risk on storms crossing over the boundary. Would like to see the HRRR runs late today to see if that model suggests a similar setup to add confidence. Will focus the greatest tornado threat along and SW of a line from College Station to Houston to Galveston.

Secondary tornado threat may exists with incoming squall line/MCS Saturday evening. Linear mode of activity should reduce the threat, but notches and local enhanced vorticity in the line could result in weak tornadoes along the line. This is what we commonly see in this part of TX that results in trees blown down and some roof damage. This threat will cover the entire region.

Wind Damage:
Plenty of wind energy will be in place so it will not take much to produce strong winds. While the initial development of supercells with a tornado risks is possible Saturday afternoon strong upper air forcing arrives Saturday evening and this will likely result in a squall line developing and moving out of central TX. Potential is there for bowing segments in the line to transport strong winds aloft to the surface resulting in corridors of wind damage. Leading edge winds of 50-70mph will be possible along this line of thunderstorms.

Heavy Rainfall/Flooding:
PWS surge to +2SD above normal by Saturday afternoon and with lift maximized from multiple sources there is little doubt it is going to rain. Heavy rainfall will be possible under the stronger cells and would expected rainfall rates of 1-2 inches likely possibly in a short period of time. This amount of rain can be handled. Fast storm motions should negate any serious flood threat and boundary orientation compared to the upper flow on Saturday is perpendicular not parallel. Only concern is potential for any warm sector supercells to anchor or train as these storms would certainly be producing copious rainfall rates.

Large Hail:
Cold pocket aloft moving over top of the warm sector does increase the hail threat, but the freezing level is fairly high and the sounding moist so think the large hail threat is the lowest risk. Hail is possible, but compared to the wind and tornado risk it is the lowest of the three.

Timing:
Thunderstorms may erupt as early as 1000am around Matagorda Bay with these storms increasing and spreading across SE TX. Area will be under the highest threat from about noon to midnight.

Will update again this evening as additional meso scale model data become available and attempt to refine/define the greatest tornado/severe threat area.

SPC Day 2 (Saturday) Severe Weather Outlook:

[/i]

[srainhoutx]

The 12Z NAM which is one of our mesoscale models that is now coming into a range we can carefully look to for possible reasonable solutions is suggesting some very rough weather across portions of S Central/SE Texas extending into Western/SW Louisiana.

The attachment 11212014 12Z NAM f39.gif is no longer available

[tireman4]

HGX AFD this morning:

FXUS64 KHGX 211008
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
408 AM CST FRI NOV 21 2014

.DISCUSSION...
HAVE SOME ONGOING WAA SHRA AS LLVL JET TAPS INTO DEEPER MOISTURE
EXTENDING SWD ACROSS THE WESTERN GULF. THIS ACTIVITY WILL PROBABLY
CONTINUE THROUGHOUT THE DAY & WE MAY EVEN SEE AN ISOLATED TSTM OR
TWO - BUT FOR THE MOST PART JUST GENERALLY LIGHT NUISANCE PRECIP.
PRECIP SHOULD TRANSITION BACK INTO CNTL TX LATER IN THE DAY AND
TONIGHT AS LLJ SHIFTS THAT WAY.

NEXT STORM SYSTEM STILL ON TARGET TO MOVE THRU SE TX ON SAT AND
SAT EVNG. SATELLITE PIX CURRENTLY SHOW THIS SYSTEM OVER SOCAL AND
SHOULD CONTINUE DIGGING SEWD ACROSS NCNTL MEXICO AND INTO CNTL TX
ON SAT. AS IT MOVES INTO SE TX SAT EVNG & NIGHT MODELS SHOW IT
TAKING A NEGATIVE TILT AS IT THEN HEADS NE INTO LA/AR. SOME OF THE
PREVIOUS MODEL RUNS SUGGESTED THIS TILT MIGHT OCCUR A BIT SOONER
AND A BIT FURTHER WEST. BUT...OVERALL DYNAMICS WITH THIS SYSTEM
STILL REMAIN QUITE POTENT WITH HIGH FAIRLY HIGH SHEAR VALUES AND
EXCELLENT DIFFLUENCE ALOFT. CAPE VALUES ARE JUST MODEST...MAINLY
500-1200 J/KG...BUT FALL WITHIN CLIMO RANGE OF PAST WINTERTIME
SEVERE WX EPISODES HERE. ANOTHER POSITIVE IN RESPECT TO SVR WX
POTENTIAL IS THIS SYSTEM WILL BE MOVING INTO THE REGION NEAR OR
SLIGHTLY AFTER PEAK HEATING. EXACTLY HOW THIS EVENT EVOLVES IS
STILL SOMEWHAT UNCERTAIN, BUT WOULD GENERALLY EXPECT SOME SCT
ACTIVITY TO DEVELOP TO OUR WEST SAT MORNING AND ACROSS OUR W/SW
PARTS DURING THE EARLY AFTN. ANTICIPATE MUCH OF THIS PRECIP TO
EVENTUALLY CONSOLIDATE INTO AN MCS/SQUALL LINE FAIRLY CLOSE, OR
IN, SE TX BEFORE MOVING TOWARD A MATAGORDA-LIBERTY-TEXARKANA LINE
TOWARD MIDNIGHT. PRIMARY SEVERE WX THREATS WILL BE TORNADOES
(MOSTLY IN DISCREET SCT CELLS OUT IN FRONT) AND DAMAGING WINDS
(BOWING SEGMENTS WITHIN TSTMS/SQUALL LINE ITSELF). HAIL WOULD BE
SECONDARY THREAT. WILL LIKELY SEE SOME HEAVY DOWNPOURS AS WELL,
BUT W/ FAST STORM MOTION OVERALL FLOOD THREAT SHOULD BE LIMITED TO
THE USUAL METRO STREETS THAT CAN`T HANDLE THE FAST HEAVY RATES.

THE STORM SYSTEM SHOULD BE OUT OF THE AREA BY SUNDAY MORNING AND
DRY SW/W FLOW IN ITS WAKE SHOULD ALLOW FOR A GOOD WARM UP. COLD
FRONT PUSHES THROUGH LATE SUNDAY NIGHT FOLLOWED BY A REINFORCING
FRONT TUESDAY. THESE FRONTS SHOULD BE MOISTURE STARVED AND BOTH
PUSH THRU RAIN-FREE. TURKEY DAY LOOKS DRY AS WELL WITH LOWS IN
40S & HIGHS 65-70. 47

&&

.MARINE...
WITH STRONG ONSHORE WINDS CONTINUING OVER THE OFFSHORE WATERS WILL
BE KEEPING THE SMALL CRAFT ADVISORY IN PLACE THROUGH THIS AFTN. AS
THE GRADIENT TIGHTENS TODAY IN RESPONSE TO THE DEEPENING UPPER LOW
OUT WEST...INCREASED WIND SPEEDS ARE LIKELY FOR THE NEARSHORE WAT-
ERS AS WELL. SCA SHOULD BE EXPANDED/EXTENDED AS THIS STRONG SYSTEM
APPROACHES. STRONG TO SEVERE THUNDERSTORMS POSSIBLE SAT AFTN/NIGHT
WITH WINDS BECOMING SW IN THE WAKE OF THIS SYSTEM ON SUN. THE NEXT
COLD FRONT IS CURRENTLY FCST TO MOVE OFFSHORE EARLY MON MORNING. 41

&&

.AVIATION...
SOMEWHAT MESSY TAF FCST EXPECTED TO CONTINUE WITH THE 12Z PACKAGE
GIVEN INCREASED MOISTURE/WEAK DISTURBANCE FROM THE WEST. WILL NOT
CHANGE TOO MUCH WITH THE VCSH WORDING THRU THE REST OF THIS MORN-
ING BUT WE COULD SEE SOME IMPROVEMENT WITH CIGS BY THIS AFTN. MAY
HAVE TO INCLUDE THE MENTION OF REDUCED VISBY (SEA FOG) FOR GLS AT
(OR AFTER) 22/06Z. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 74 63 73 58 78 / 60 30 90 80 0
HOUSTON (IAH) 75 63 76 62 79 / 50 20 80 90 0
GALVESTON (GLS) 73 66 74 67 78 / 30 20 70 90 0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR THE
FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP
CHANNEL 20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO
FREEPORT 20 TO 60 NM.

&&

$$

[Andrew]

The biggest determining factor tomorrow for severe weather, especially in respect to Tornadoes is cloud cover and "junk convection in the morning". Almost all models agree that large shear values will be present but the biggest question will be stabilization and CAPE. Models continue to struggle with WAA so I suspect this will continue but as we head into the afternoon it will be key to keep an eye on satellite to see where cloud coverage is.