July 2014: Stalled Front/ Rain Chnaces To End July

[kayci]

Kayci has rain!

[BlueJay]

Kayci has rain!

Great news Kayci! Here's hoping we all will get some of the goodness too

[srainhoutx]

Keep an eye on the boundary that runs roughly from Galveston Bay on NW to near Childress, the Texas Panhandle and on up into the Colorado front range. Anywhere W of the boundary into W Texas has a rather unstable air mass with higher PW's near or slightly above the 2 inch mark. To the N and E of the boundary drier more stable air remains and should be a bit slower to moisten up until tomorrow. I had a heavy shower drop almost 1/4 inch of rain a couple of hours ago and you can see the cumulus clouds building in an uncapped environment.

[Andrew]

Pretty evident where the boundary is located when looking at dewpoints and PWs. Here is the current PW setup across the state:

[BlueJay]

I wasn't quite sure about the "PW" abbreviation that srain and Andrew were using. So, I went looking.

From the National Weather Service Weather Forecast Office
http://www.crh.noaa.gov/dtx/afdterms.php#pw

Precipitable Water: (PW, PCPTBL WTR or H2O) Total amount of water vapor in a layer of air, expressed in inches. Normally taken between 1000 and 500 mb. Higher values of precipitable water indicate a deep moisture layer, increasing the potential for heavy precipitation amounts.

This sounds like rain!

[jasons2k]

NWS AFD:

RAINFALL AMOUNTS WILL BE TRICKY AS THERE COULD BE A TIGHT GRADIENT BETWEEN THOSE WHO GET RAINFALL AND THOSE WHO DO NOT.

So, what else is new?

[srainhoutx]

Jason, I thought the HGX issued one of their better detaled, informative and well written AFD's in a long time. It was interesting to see their thoughts on how 1 to 3 inches of rain could turn into 5 inches if training storms develop. Obviously Thursday night into Saturday could turn out rather complicated as steering currents collapse as the short wave exits stage left.

[jasons2k]

I wasn't knocking the NWS...or the discussion...just the usual feast or famine on the rainfall.

Big storms are once again just up the road. That .13" didn't do anything for my lawn - it looks worse today than it did yesterday.

[djjordan]

Missed out on my lawn today, but I'm pretty sure I'll get something out of this before the week is out. This is going to be an interesting end of the week weatherwise for sure.

[Ptarmigan]

Current model consensus shows quite the spread. Starting with the NAM, the shortwave that is currently located in the Montana area will come through central Oklahoma a lot less amplified than both the GFS and Euro are showing. Timing also seems to be an issue resulting in a less significant (and farther north) MCS through North Texas tomorrow evening. Downstream a couple of vort maxes (area where vorticity is highest causing rotation in the atmosphere) try to develop from the Southeastward moving shortwave, they are not nearly as defined as the GFS and Euro.

Moving on to the GFS, it is the most bullish out of all three models in amplification of the trough and vort maxes across NW Texas. Similar to the Euro, it develops a surface low in NW Texas but location and intensity of the most northern vort max will determine the movement of tomorrow night's MCS. As of now the GFS wants to create a very strong MCS moving across the Texas Panhandle into the DFW area and points north. Rainfall rates are pretty extreme at certain points in the MCS progression with estimates of up to 4inches. I suspect convective feedback is an issue for the GFS and it's having trouble handling the projected MCS.

Finally the Euro shows a nice middle ground between the NAM and GFS. The synoptic setup is similar to that of the GFS and looks realistic. The vort maxes that develop aren't overwhelming but provide enough rotation and moisture to maintain a MCS. The weak surface low from the EURO is furthest west and that pushes the MCS furhter Southwest, effecting more of central Texas.

As for SE and central Texas, progression of the MCS will be key to how far south the cold front makes it. Right now I would throw out the NAM solution and focus on a blend of the GFS and Euro. Both stall the boundary across the northern counties of SE Texas, creating multiple days of scattered storms. What will be noteworthy to watch, is how the southern vort max progresses. Both the GFS and NAM suggest it could track South then East across much of Texas. With PWs already in the 2+ range, this additional organization could spark organized storms throughout the area. Either way rain chances should increase towards the end of the workweek with locally heavy rainfall.

Like it.

[Ptarmigan]

Jason, I thought the HGX issued one of their better detaled, informative and well written AFD's in a long time. It was interesting to see their thoughts on how 1 to 3 inches of rain could turn into 5 inches if training storms develop. Obviously Thursday night into Saturday could turn out rather complicated as steering currents collapse as the short wave exits stage left.

I would not be surprised if over 5 inches of rain falls, possibly up to 12 inches. The PW value is quite high and steering current is weak.

[srainhoutx]

Morning Update From Jeff:

Active 24-36 hours for SE TX as deep moisture and a strong short wave combine to produce widespread rainfall.

Radar is already active this morning with showers moving northward off the Gulf of Mexico mainly east of a line from Freeport to Hempstead. Stalled weak frontal boundary is along a line from roughly Lake Charles to Waco or across the NE 1/3rd of our region. Strong short wave is noted in water vapor images over WY dropping SE into the central plains helping to focus widespread slow moving heavy rainfall over N and NC TX this morning. Storm totals north of Dallas along I-45 are already nearing 10 inches.

Extremely moist air mass will be spreading into SE TX today with PWs rising from around 2.0 inches to near 2.3 inches by this evening. Only modest heating will be needed to set off thunderstorms and expect an increase in activity in the 1100am-100pm time period. Main threat will be lightning and very heavy rainfall. Storms this morning over NW Harris County were moving at nearly 25mph and were still able to produce a quick .50 of an inch of rainfall.

Large scale lift arrives late tonight into early Friday as the WY short wave digs into N TX. Expect a large MCS to develop over N and C TX this afternoon and track into SE TX tonight. System will slow as it moves into the area greatly increasing the threat for heavy rainfall especially NE of a line from College Station to Liberty. Not sure exactly how things will play out on Friday as various model solutions are at play and with meso scale nature of the events (outflow boundaries) it is hard to determine where exactly any sustained training of storms may develop. MCS may have enough push to move to the coast early in the day which would tend to limit the heavy rainfall threat or if may “run out of steam” and slowly stall across the area leaving a well defined boundary to continue to focus heavy rainfall into Friday afternoon. Given PWS over 2.0 inches there is certainly a threat for excessive rainfall and flooding, but the main threat appears to be just north and northeast of the region where lift will be maximized from the short wave.

Will go with widespread rainfall amounts of 1-2 inches this afternoon through Friday afternoon with isolated amounts of up to 5 inches especially across our NE counties from roughly Huntsville to Liberty. Amounts could even be higher than that as seen this morning in N TX so the heavy rainfall threat will have to be watched carefully over the next 12-24 hours. Additionally, excessive forecasted QPF over N TX may generate some significant river rises with flood waves possibly reaching SE TX early next week.

[srainhoutx]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT THU JUL 17 2014

VALID 171300Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/WRN TX...

...SUMMARY...
SCATTERED THUNDERSTORMS...A FEW SEVERE...ARE EXPECTED TO DEVELOP
ACROSS WEST-CENTRAL INTO NORTH-CENTRAL TEXAS. OTHER ISOLATED STRONG
STORMS ARE POSSIBLE ACROSS MUCH OF THE REMAINDER OF TEXAS INTO
SOUTH-CENTRAL NEW MEXICO.

...SYNOPSIS...
IN MID-UPPER LEVELS...BROADLY CYCLONIC FLOW WILL PERSIST OVER MOST
OF ERN CONUS. NONETHELESS...CONSIDERABLE HEIGHT RISES WILL OCCUR
ACROSS UPPER MS VALLEY...GREAT LAKES AND NERN STATES AS STG
SHORTWAVE TROUGH CURRENTLY OVER PA LOSES AMPLITUDE AND EJECTS NEWD
ACROSS NEW ENGLAND. WEAKER BUT STILL WELL-DEFINED SHORTWAVE TROUGH
WAS APPARENT IN MOISTURE-CHANNEL IMAGERY OVER CENTRAL HIGH
PLAINS...FCST TO LOSE AMPLITUDE GRADUALLY AS IT MOVES SEWD TO OK AND
SWRN MO BY END OF PERIOD. MEANWHILE...SHORTWAVE TROUGH NOW OVER WRN
BC WILL PROGRESS ESEWD TO SK BY 12Z...CONTRIBUTING TO GEN TSTM
POTENTIAL OVER NRN ROCKIES AND NRN HIGH PLAINS...THOUGH STRONGEST
DEEP-LAYER FORCING AND MOST VIGOROUS CONVECTION WITH THIS SYSTEM
SHOULD REMAIN N OF CANADIAN BORDER.

AT SFC...11Z ANALYSIS SHOWED COLD FRONT OFFSHORE NEW ENGLAND AND
SWWD ACROSS SERN GA TO NEAR MS RIVER MOUTH. WARM FRONT WAS DRAWN
NWWD ACROSS SWRN LA AND E TX...INTERCEPTED OVER DFW METROPLEX BY
OUTFLOW BOUNDARY FROM HEAVY-RAIN-PRODUCING TSTMS THAT HAVE BEEN
OCCURRING OVER THE DTO AREA. JAGGED OUTFLOW BOUNDARY EXTENDED FROM
THERE WWD TO JUST NW MWL THEN SWWD BETWEEN BPG-MAF.

...TX...
CONVECTIVE SCENARIO TODAY IS MESSY WITH FOCI SUBTLE AND UNCLEAR S OF
OUTFLOW BOUNDARY AND WARM FRONT. NRN PORTIONS OF SVR OUTLOOK HAVE
BEEN CARVED AWAY DUE TO SUBSTANTIAL STABILIZATION FROM OVERNIGHT
ACTIVITY AND IMPROBABILITY OF ENOUGH RECOVERY TODAY TO SUPPORT
ORGANIZED SVR THREAT IN AREAS NEAR RED RIVER. OTHERWISE...WIDELY
SCATTERED TO SCATTERED TSTMS IN CLUSTERS ARE POSSIBLE THROUGH LATE
EVENING...SOME OF WHICH MAY PRODUCE DAMAGING GUSTS AND LARGE HAIL.
TORNADO RISK IS VERY CONDITIONAL ON MESOBETA- TO STORM-SCALE
PROCESSES...AND LOCALIZED BOUNDARY INFLUENCES YET TO TAKE SHAPE.

OUTFLOW BOUNDARY STILL IS MOVING SWD BUT DECELERATING ACROSS BIG
COUNTRY AND NERN PERMIAN BASIN REGIONS. ITS AFTN POSITION IS
CRUCIAL TO SVR POTENTIAL TODAY BUT STILL UNCERTAIN...GIVEN POTENTIAL
FOR MORE ELEVATED CONVECTION TO FORM TO ITS N THROUGH FORENOON
HOURS. WIDELY SCATTERED/ELEVATED CONVECTION ALSO HAS DEVELOPED OVER
WARM SECTOR...GENERALLY IN BPG-SNK-DYS REGION...WITH LARGER AREA OF
PRECIP AND EMBEDDED TSTMS TO ITS E OVER NRN HILL COUNTRY.
WARM-SECTOR CONVECTION GENERALLY SHOULD MOVE ESEWD-SEWD TO ALLOW FOR
SOME DIABATIC HEATING TODAY ACROSS W-CENTRAL TX...WHERE LOW-LEVEL
LAPSE RATES WILL BE STEEPEST AND SFC-BASED/AFTN DEVELOPMENT MOST
PROBABLE.

S OF OUTFLOW BOUNDARY ACROSS W-CENTRAL TX...STG DIRECTIONAL SHEAR
WILL EXIST...CONTRIBUTING TO FAVORABLE DEEP SHEAR FOR ORGANIZED
MULTICELLS AND ISOLATED SUPERCELLS...DESPITE SHALLOW LAYERS OF SPEED
WEAKNESSES APPARENT IN FCST LOW-MIDDLE-LEVEL WIND PROFILES. FCST
SOUNDINGS INDICATE LAPSE RATES ALOFT WEAKEN AND WARM-RAIN CLOUD
LAYERS DEEPEN WITH EWD EXTENT. AS SUCH...HAIL POTENTIAL IS
RELATIVELY MAXIMIZED OVER WRN 1/2-2/3 OF CATEGORICAL SLGT AREA.

FARTHER SE...HODOGRAPHS ARE EXPECTED TO ENLARGE LATE THIS AFTN INTO
EVENING ACROSS PORTIONS S-CENTRAL/SE TX...AS 1-2 KM AGL FLOW
STRENGTHENS...WHILE VERY MOIST BOUNDARY LAYER STILL SUPPORTS
SFC-BASED PARCELS. AS SUCH...CONDITIONAL BUT NONZERO TORNADO RISK
MAY DEVELOP WITH ANY RELATIVELY DISCRETE/SUSTAINED TSTMS IN THAT AIR
MASS.
..EDWARDS/ROGERS.. 07/17/2014

[srainhoutx]

MESOSCALE PRECIPITATION DISCUSSION 0209
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
854 AM EDT THU JUL 17 2014

AREAS AFFECTED...PORTIONS OF CNTRL AND NRN TEXAS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 171253Z - 171845Z

SUMMARY...THE FLASH FLOOD THREAT WILL CONTINUE THROUGH 18Z WITH
MODEST OVERRUNNING OF A STATIONARY FRONT IN THE PRESENCE OF
ANOMALOUSLY DEEP MOISTURE. SLOW MOVEMENT OF AN ASSOCIATED UPPER
TROUGH WILL KEEP FAVORABLE CONDITIONS IN PLACE INTO THE EARLY
AFTERNOON.

DISCUSSION...SSWLY 925-850 MB FLOW OF 20-30 KTS AS SAMPLED BY 12Z
RAOB DATA AND VAD WIND PROFILES AT KGRK AND KFWS CURRENTLY EXISTS
ACROSS MUCH OF CNTRL TEXAS IN THE PRESENCE OF PRECIPITABLE WATER
VALUES NEAR OR ABOVE 2 INCHES. THIS MOISTURE IS ABOUT 2 STANDARD
DEVIATIONS ABOVE THE MEAN FOR THIS TIME OF YEAR...WITH SAMPLED
SBCAPES OF ROUGHLY 1000-1500 J/KG PER 12Z KFWD SOUNDING SOUTH OF A
STATIONARY FRONT. THIS ENVIRONMENT IS IN PLACE AHEAD OF A SLOW
MOVING 700 MB WAVE OVER WRN OKLAHOMA WHICH IS FORECAST TO VERY
SLOWLY TRACK EAST TODAY...REACHING CNTRL OKLAHOMA BY THIS EVENING.

WHILE THE HEAVIEST RAINFALL IS NOT EXPECTED TO BE WIDESPREAD
ACROSS THE THREAT AREA...THERE ARE PORTIONS OF THE HIGHLIGHTED
REGION THAT HAVE RECEIVED 3 HOUR RAINFALL RATES OF 5 TO 6 INCHES
OVERNIGHT...AND CONTINUE TO RECEIVE MODERATE TO HEAVY RAINFALL
THIS MORNING. THROUGH THE REMAINDER OF THE MORNING INTO EARLY
AFTERNOON...CONDITIONS ARE EXPECTED TO PERSIST WITH A SLOW EWD OR
SEWD DRIFT PER RAP FORECAST CORFIDI VECTORS. THE 00Z HRW ARW AND
RECENT RUNS OF THE HRRR SUGGEST ADDITIONAL RAINFALL MAXIMA OF 4-6
INCHES IN THE VICINITY OF THE RED RIVER TO THE NORTH OF THE DFW
METROPLEX THROUGH 19Z...WITH POTENTIAL FOR LOCALIZED FLASH
FLOODING TO THE SOUTH WHERE RECENT COOLING ON IR IMAGERY HAS BEEN
OBSERVED.

OTTO

ATTN...WFO...SHV...TSA...FWD...OUN...EWX...SJT...

[srainhoutx]

A rather interesting and potentially active weather day lies ahead across our Region. The latest meso as well as surface analysis suggest two areas of low pressure currently analyzed across the Lone Star State. One is near Wichita Falls and another further S nearing the Hill Country ESE of San Angelo which the guidance did not predict or expect has developed. We will need to monitor the short range meso guidance and see if they detected the further S surface low and how that may change the future forecasts further S across Central and SE Texas on into Louisiana.

[wxman57]

I measured 2.45" yesterday afternoon in Westbury. That makes nearly 5" for July. Even heavier rain likely over the next 2-3 days.

[unome]

crazy rainfall totals around Denton

http://www.srh.noaa.gov/wgrfc/

http://www.srh.noaa.gov/ridge2/RFC_Precip/

RFCs derive the "Observed" precipitation field using a multisensor approach. Hourly precipitation estimates from WSR-88D NEXRAD are compared to ground rainfall gauge reports, and a bias (correction factor) is calculated and applied to the radar field. The radar and gauge fields are combined into a "multisensor field". Human quality control then seeks to remove gages that appear to be malfunctioning as well as radar artifacts that may appear. This is done on an hourly basis. In areas where there is limited or no radar coverage, satellite precipitation estimates (SPE) can be incorporated into this multisensor field. The SPE can also be biased against rain gauge reports.

[txflagwaver]

FINALLY getting some rain here. Lots of thunder and lightning as well.

[BlueJay]

We are currently enjoying a heavy rainfall complete with some thunder!
This looks like it will be a real soaker for my backyard!

[jasons2k]

All the yellows and reds skirted right by me with the first line. And now that gaping hole along I-45 in the second line looks like it will pass right over me too. Maybe tonight/tomorrow I'll get my turn.

Edited: and just like that, line #2 is through with little fanfare. It's moving so fast unless you get a big red blob right over you, you probably won't accumulate much rain.