May 2017: Memorial Day/End Of May Outlook

[MontgomeryCoWx]

I did upper 40s and rain for the Kentucky Oaks and Derby last weekend. It was refreshing!

[Katdaddy]

A few strong storms possible this afternoon mainly N and W of Houston metro where the SPC has a marginal risk area. Our next front will be moving across TX today and approach SE TX tonight. This front will move off the coast Friday morning bringing clearing skies and lower humidity however temps will remain warm through the weekend. TS Adrian has been downgraded to a TD and expected to dissipate later today.

[srainhoutx]

Thursday morning briefing from Jeff:

Omega block upper air pattern that has been in place for the last week is breaking down allowing a slow moving storm system over the SW US to eject across the plains today into Friday.

Low level moisture has returned to the region below a capping inversion while high level moisture spills across the state from the Pacific on the southeast flank of the upper air storm system over portions of NM and W TX this morning. A surface cool front will progress through TX today and off the coast sometime on Friday. Air mass will likely remain capped today with isolated showers and possibly a thunderstorms late this afternoon with enough surface heating. Overall rain chances look fairly low with the front (20-30%) tonight into early Friday as the main forcing for lift is aimed that the central plains with little to break the cap over our region.

Much drier air mass will filter into the area late Friday with weekend dewpoints falling into the 50’s which will result in overnight lows down into the lower 60’s by Saturday and Sunday mornings. High temperatures will still make the mid 80’s given the rapid heating of the dry air mass and clear skies.

Next Week:
Another upper level storm system drops into the SW US by early next week and once again moisture will begin to return off the western Gulf of Mexico. Will keep rain chances out Monday and maybe Tuesday then begin to raise chances on Wednesday. GFS and ECMWF are not in much agreement on how the upper air pattern will play out next week and just how much rainfall is possible over the region. ECMWF wants to develop a coastal trough and focus heavy rainfall along the coast and possibly into SE TX toward the end of next week while the GFS is mostly dry. Both of these completely opposite solutions appear possible at this time. One other item to keep an eye on is the pool of moisture associated now tropical depression Adrian south of Mexico. If this moisture pool remains in that area as expected for the next several days it could become entrained within the return flow early next week.

[srainhoutx]

Thursday afternoon update from Jeff:


SPC has issued a Severe Thunderstorm Watch until 1000pm for the northern counties of SE TX: Trinity, Walker, Madison, Houston, Grimes, Brazos, and Burleson.

Thunderstorms are slowly increasing in region of increasing instability south of a slow moving cold front over NC TX. Air mass has become unstable and capping appears to be eroding which may result in the formation of strong to severe thunderstorms over the next few hours. Main threat will be large damaging hail and strong winds although an isolated tornado cannot be ruled out. Storms may grow upscale this evening into a line and track ESE/E into portions of E TX and the northern portions of SE TX with an increasing wind damage threat.


Severe Thunderstorm Watch Outline and Radar Overlay:

[jasons2k]

I'm glad I watered.

[Cromagnum]

I'm glad I watered.

Yep, this persistent cap is bullshit already. Hardly any rain in April or May so that June-September can scorch the rest.

[Katdaddy]

Beautiful SE TX weather arrives this morning behind the front this morning and will remain through the weekend. Strong storms pushing into the coastal waters SE and E of Galveston currently. 19 days until the 2017 hurricane season. Day 6 of hurricane preparedness this week is important. Teamwork is very important before, during, and after a hurricane.

Day 6 of 2017 Hurricane Preparedness Week: Check On Your Neighbor

Many rely on their neighbors after a disaster, but there are also many ways you can help your neighbors before a hurricane approaches. Learn about all the different actions you and your neighbors can take to prepare and recover from the hazards associated with hurricanes. Start the conversation now with these Neighbor Helping Neighbor strategies.

[Cromagnum]

We almost need some tropical mischief just to have a chance at rain.

[DoctorMu]

We almost need some tropical mischief just to have a chance at rain.

Not much relief on the long term GFS through the end of the month. We have some deep moisture on Wednesday elevating our chances of rain (50% in CLL).


The persistent cap may partly reflect the 10 year drought and CC. Still, the last couple of years tropical mischief has provided a few May and June deluges. We need as much natural water as possible in the ground before July. Far too much Na+ in our sprinkler water, making it alkaline.



.PREV DISCUSSION... /ISSUED 257 PM CDT Sat May 13 2017/

SHORT TERM...
Today`s surface analysis at 19Z was fairly simple with broad weak
high pressure over much of the Plains into Texas. Over SE Texas
light north winds have allowed for some mixing and dewpoints in
the upper 50s to low 60s. Upper level analysis has ridging aloft
over much of Texas and the Plains for that matter. Overall weather
conditions are so quiet that I literally heard a pin drop in the
office. Plus the airmass is pretty stagnant and we are having
ozone action days.

Upper level ridge looks to hold over much of the area through
Monday night. Southerly return flow sets up tomorrow and look for
moisture return to continue for much of the week. Overall this
allows for temperatures to be near or 3 to 5 degrees above normal.

Overpeck

LONG TERM...
The upper level ridge should break down Tuesday into Wednesday
and shift over Florida and SE U.S. A short wave trough should move
out of the southern Rockies into the Plains late Tuesday. This is
also when the subtropical jet becomes more active over the
southern half of Texas. Forecast will keep ongoing rain chances
mainly for Wednesday. GFS shows a good surge of moisture with
precipitable water values 1.5 to 1.9 inches. Overall the pattern
supports decent rain chances mainly north of Houston for the
middle of the week. The stronger upper level ascent looks to
remain even farther north over the Plains Tuesday night and then
another upper level low deepens over the Rockies going into
Thursday. Look for rain chances of 20 to 30 percent to continue
for the end of next week. Best chances look to be Wednesday with
the initial surge of moisture. There may be a threat for heavy
rainfall Wednesday through the end of the week, but models seem to
be keying on Wednesday the most. One thing that seems to be
missing from the atmospheric set up for heavy rain is a stalled
frontal boundary. Quite possible that outflow from previous
convection could provide this on the mesoscale but still plenty of
time to figure out these details. For now the heavy rainfall
potential for Wednesday remains just a potential and something to
monitor.

[srainhoutx]

Monday morning briefing from Jeff:

After several weeks of generally nice weather…the upper air pattern will undergo changes that will allow a return of thunderstorms across the southern plains this week into next week.

Upper level blocking with high pressure over the southern plains the last week is shifting eastward allowing the semi-stationary upper level trough over the SW US to edge closer to the southern plains. The initial trough will eject into the plains on Wednesday, but a secondary trough will quickly dig back into the SW US late this week and very slowly move into the plains this weekend into early next week. Locally onshore winds have already returned to the region allowing a slow but steady increase in Gulf moisture. Air mass will slowly moisten over the next 48 hours before a surge of deeper moisture arrives on Wednesday. Will raise rain chances to 40% for Wednesday as this deeper moisture arrives and SE TX may get skirted by the tail end of lift from the ejecting SW US trough. Main dynamics with this system are aimed more toward the central plains. This week will provide near daily chances of severe weather including tornadoes across the plains.

Secondary trough digs into the SW US Thursday and Friday and this will position a SW flow aloft across the region. Weak disturbances in this flow aloft combined with the W TX dryline may result in complexes of thunderstorms developing to our west each afternoon and moving eastward during the overnight hours. Big questions at this time range are do any of these complexes make it as far east as SE TX or do their outflow arrive into the region during peak heating. Given a moist and generally unstable air mass in place from Wednesday onward will have to keep an eye on such potential.

Sub-tropical ridge aloft will shift a bit eastward this weekend and this will allow a very slow motion of the SW US trough eastward. A surface cold front will move into the state from the NW helping to act as a trigger for deep convection. Upper air parameters may become more favorable also for thunderstorm formation along with continued ejecting short wave disturbances out of the mean trough to our west. Timing of this all remains in question, but models are starting to key in on Saturday as the first day for potential widespread thunderstorms. Also starting to see a heavy rainfall signal in the models with QPF maxes of 3-5 inches over the weekend likely from some sort of slow moving thunderstorm complex (something to watch very closely).

Very slow movement of the upper trough will continue to favor rounds of thunderstorms into early next week allowing rainfall totals to pile up. Each rough will likely pose some risk of severe weather given it is mid May and instability is generally decent this time of year. QPF amounts are highest across central TX into OK this week and enough rain may fall, even though grounds are generally dry, to activate run-off and rises on upstream rivers and creeks. Heavy rainfall signal drifts deeper into SE TX this weekend into early next week.

[tireman4]

000
FXUS64 KHGX 151731
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1231 PM CDT Mon May 15 2017

.AVIATION...
Not a lot of changes from previous TAF forecast thinking that the
intrusion of BKN/OVC mid/high clouds from the west overnight will
help temper the development of patchy fog through early Tues morn-
ing. Otherwise the quiet weather pattern will remain in place and
VFR conditions will prevail. 41

&&

.PREV DISCUSSION... /ISSUED 1037 AM CDT Mon May 15 2017/

Today is shaping up to be another quiet day weather-wise with
temperatures in the upper 70s and dewpoints in the low/mid 60s.
Moisture should only increase with southerly winds today. Upper
level ridge over much of Texas should suppress convection over the
area so only expecting flat cumulus development today. High
temperatures should reach the mid/upper 80s again and look for a
repeat tomorrow.

Afternoon forecast update will take a look at rain chances
Wednesday through the weekend. Only changes to the forecast for
this morning are to ongoing temperature, dewpoint and sky trends.

Overpeck

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 88 67 89 71 84 / 0 0 10 20 40
Houston (IAH) 87 68 87 73 85 / 0 0 10 10 40
Galveston (GLS) 81 74 83 77 83 / 0 0 10 10 20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

[DoctorMu]

The GFS has changes its tune a bit and has a more dynamic weather pattern by the end of the month, including a couple of cold fronts. Trough sets up in the west with the block to our east. While the greatest chance of pricip in the next 2 weeks is allegedly in the NW HGX area, the outlook is more hopeful than yesterday. Wednesday and Sunday appear to have the best chance of rain this week.

[Katdaddy]

GOM moisture inflow will continue to increase across SE TX through the rest of the week with some scattered thunderstorms possible tomorrow and Thursday across portions of SE TX. The upcoming weekend is looking more unsettled but will be mesoscale driven.

[srainhoutx]

Best chance of showers and storms looks to be along and West of the I-35 Corridor into the weekend where there are several days of severe storm chances before the frontal boundary slowly sags SE into Central Texas. I still believe it is too soon to know with any certainty where the greatest chance of rainfall will occur regarding our sensible weather in SE Texas other than the College Station to Lake Livingston areas which have been the lucky locations the past several events. I will wait until Friday before believing any of the models predicting heavy rainfall across Metro Houston to the Coast...

[srainhoutx]

Tuesday midday weather briefing from Jeff:

Upper air pattern continues to transition toward one of a much more active period of weather coming to TX compared to the recent week.

First upper level trough will eject into the plains today and Wednesday only to be replaced with a secondary upper trough over the SW US by this weekend. While the air mass is certainly moistening over the area, it is capped off to deep convection via a warm layer of air in the mid levels. A surge of deeper moisture on Wednesday may help to promote a few showers under the capping inversion along with the arrival of an outflow boundary from today’s dryline convection over W TX. Meso models general show the arrival of the west TX convective line into the western counties of SE TX early Wednesday before forcing weakens and the line generally collapses.

Calm weather on Thursday and Friday although dryline storms will likely erupt each afternoon and will have to at least watch for any potential for any sort of thunderstorm complex to approach from the W/NW during this period.

Weekend-Early Next Week:

Main attention is starting to focus on this time period as the secondary very slow moving upper level trough lifts into TX allowing a surface frontal boundary to slowly advance into the region. Surface front will act as a trigger for deep convection as early as Saturday, but more likely on Sunday. Mesoscale processes will likely begin to take over and drive convective events during this period as outflow boundaries override the frontal boundary. Air mass will remain very moist (PWS of 1.8-2.0 inches) and unstable throughout the entire period which will support numerous thunderstorms. Heavy rainfall signal continues to show up in model forecast and confidence is starting to grow given the increasingly favorable setup that flash flooding could be possible. Combination of a surface boundary nearly parallel to the upper level SW flow aloft, deep tropical moisture in place, and an upper level storm system nearly stalled just to our west allowing good upper level divergence are some classic heavy rainfall parameters for this area. Would like to see a stronger 850mb transport flow off the Gulf and if then begins to show up in the model guidance this would suggest an even stronger flash flood signal. Concern would be some sort of slow moving thunderstorm complex either Saturday night or Sunday night perpendicular to the 850mb low level jet.

Severe threat also looks possible this weekend with good instability in place. Main threat would likely be large hail and wind damage given the potential for lines of storms versus tornadic supercells.

Forecast into early next week is of low confidence as models attempt to resolve the meso scale influences over the local area. Looks like another surface boundary may approach the area sometime around Tuesday which would only serve promote additional thunderstorms.

[jasons2k]

From the NWS:

May has been relatively cool when compared to the past couple of months with the average monthly temperature (through the 14th) about 2 degrees cooler than normal. 10 out of the first 15 days of the month have been cooler than normal.

However, the year to date average temperatures are still the warmest on record for all four first order climate sites.

[Katdaddy]

Partly sunny skies and breezy across SE TX today. A weakening line of scattered showers and thunderstorms across Central TX will continue to fall apart as they approach NW portions of SE TX this morning. Thunderstorm chances will increase through the weekend with a potential for heavy rainfall.

The big weather story will be the continued severe weather across the Plains through the rest of the week. 27 tornadoes reported yesterday across the Plain with loss of life in WI and significant damage in Elk City, OK The SPC has another Moderate Risk area tomorrow across NW OK and SW KS. If you have friends and family in that area; make sure the are weather aware.

[jasons2k]

Rain chances for today went poof!

[DoctorMu]

Rain chances for today went poof!

Looks like another bust here as well with the dryline. NW Harris Co could see a few midday showers. Maybe some daytime heating shower tomorrow for CLL.

[tireman4]

000
FXUS64 KHGX 171444
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
944 AM CDT Wed May 17 2017

.UPDATE...
Morning soundings from the neighbors showed fairly dry atmosphere
above a pretty stout cap this morning. This can also be easily
inferred from the appearance of radar, where most rain approaching
Southeast Texas is fizzling before moving into our area of
responsibility. CRP`s sounding looked a bit more saturated, so
that showers are better holding together to our west is not a big
surprise.

Have reconfigured PoPs to match these trends a little better for
today and tonight. Best chance for some showers going forward will
be along our western boundary where the environment is a little
more supportive. Also tweaked temps to match obs, but changes here
were not very substantial. Changes to winds include keeping winds
up a little more over the water and immediate coast, which
necessitated a longer small craft advisory. However, winds are low
enough on the coast that the wind advisory was able to expire.

Luchs


&&


.PREV DISCUSSION... /ISSUED 458 AM CDT Wed May 17 2017/

DISCUSSION...
A very tight onshore pressure gradient between the Bermuda
Subtropical High and a deepening low (trough/cold front) over the
western South Plains states has created an overnight moderate to
strong surface wind field. Strongest winds are closer to the coast
where a Wind Advisory will be in effect through 8 AM this morning.
Convection that fired along the west Texas dry line yesterday is
falling apart as it runs into a more dry and capped downstream
environment over Central Texas. There are slight to low chances
that some discrete cells from this activity nearing I-35 this hour
may hold together and enter our warming and becoming increasingly
unstable northwestern forecast area during the morning daytime
hours. Another element to consider will be jet placement as the
southern branch comes right across the state this afternoon...possibly
overlaying more favorable diffluence over the region during peak
heating. Today`s maximum temperatures should achieve the mid to
upper 80s once again...with overnight overcast and a well-mixed
near surface layer keeping regional minimum temperatures in the 70s.

The northeastern ejection of this morning`s Desert SW upper trough
will allow a secondary upper low moving south out of the northern
Rockies to fall into its wake Thursday. This upper low will meander
over the Rockies through Saturday before exiting north into the
Great Northern Plains states. As this occurs...a weak cold front
will slowly travel across the state this weekend. A general unsettled
pattern will evolve through the weekend...with a modest chance of
more widespread rain occurring from late Saturday through as late
as Monday. Not particularly confident on the `where` and `why` as
of this morning...but precipitation forming along or just ahead
of a Central Texas frontal boundary/low level area of convergence
will slowly advance into our area going into Sunday. Overall
moisture should not be a problem with progged greater than 1.5 inch
pwats within an unstable downstream air mass. If the aforementioned
boundary does sag into the region Sunday...there should be enough
focus within a modeled weakly-sheared regional atmosphere with 5.5
to 7 C/km lapse rates (near 2.5k J/kg CAPE) leading to -7 to
-9 lifted indices and lower 30 K indices. Inverted V soundings
indicate that the strongest storms may put down some decent wind
but slow clustering cell movement depict the highest threat being
that of high rainfall leading to early week flooding concerns.

Late period general troughiness over the Southern Plains (ridging
remains over Mexico) signals that unsettled weather will likely
linger on into mid-week. Shortwave disturbances rotating around
the base of the trough Tuesday and Wednesday keep POPS in the low
category range. A more wet and overcast pattern from Sunday onward
into late May will shave a few degrees off daily maxT readings...closer
to the middle 80s...with downward trending minTs eventually falling
back into the interior 60s after several days in the lower to
middle 70s. 31

MARINE...
Localized tight pressure gradient is allowing for some strong
onshore winds this morning, with gusts to close to gale force at
times. These should slightly diminish later this morning, but in the
meantime small craft advisories will remain in effect. In addition,
we plan on issuing a beach hazards statement for strong rip currents
& elevated tide & surf thru the early afternoon hours. Tide levels
are running 1 ft above normal. With high tide at 1018am along the
Galveston beachfront, we may see water get right to the HWY 87/124
intersection with the assistance of wave runup. But not expecting
substantial problems elsewhere. The remainder of the fcst looks
about the same w/ moderate onshore winds & elevated seas continuing
into Sat. May see a combo of caution/advisory flags between now and
then. A weak frontal boundary will approach the coast late Sunday,
but it`s unclear if or how far offshore it`ll push just yet. 47

AVIATION...
MVFR cigs have settled in across the region. These should lift back
above 3000ft by lunchtime. Remnants of the precip currently to our
nw will be making its way into se tx 13-16z, but should be weakening
as it does so. There`s a pretty good chance it dissipates before making
it into the Houston terminals. There may be some lingering spotty shra
around into the aftn hours. Otherwise, expect a transition back to
MVFR ceilings later this evening. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 85 73 90 73 90 / 20 10 20 20 20
Houston (IAH) 85 74 88 74 88 / 10 10 10 10 20
Galveston (GLS) 82 77 85 78 85 / 10 10 10 10 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 6 PM CDT this evening
for the following zones: Galveston Bay...Matagorda Bay.

Small Craft Advisory until 4 AM CDT Thursday for the following
zones: Coastal waters from Freeport to the Matagorda Ship
Channel out 20 NM...Coastal waters from High Island to
Freeport out 20 NM...Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.

&&

$$

Discussion...25