Texas Spring 2016

[TheProfessor]

All are Forecasted Soundings of the 12z NAM at 63 hours.

Denton Sounding

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Dallas Sounding

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Fort Worth Sounding

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Austin Sounding

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San Antonio Sounding

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Still a lot can change between now and Tuesday.

[TheProfessor]

Also if the Nam is handling the Cap well then it looks like it won't help much, it looks to break around 18z Tuesday in time for storms but it doesn't break early in the morning to allow for convection like we sometimes get.

[gboudx]

Update from Jeff Lindner:

Slow moving significant storm system to impact TX much of this week.

Severe weather and flooding rainfall over multiple days will be possible.

Discussion:
Powerful upper level storm system arriving into CA this morning will move SE into the SW US on Monday and then into MX on Tuesday where it slows and deepens. SE winds are already underway over TX helping to transport moisture into the region from the Gulf of Mexico, but this current moisture advection is shallow and trapped beneath a strong 800mb inversion (cap). This capping will maintain itself into Monday afternoon, before much more significant moisture arrives late Monday into early Tuesday. Moisture values climb from 1.0 in of PW to nearly 1.8 inches of PW by Tuesday afternoon which would be near record values for early March. Additionally, dry layer above 800mb rapidly moistens on Tuesday with the air column becoming nearly saturated by Tuesday afternoon. Upper level forcing will spread out of MX and across TX Tuesday-Thursday with several surface low formations and rounds of thunderstorms. Capping in the mid levels will be eroded by Tuesday afternoon from incoming cold air aloft along with several upper air disturbances and jet streaks. Upper winds become strong divergent early Wednesday morning and think this is when a very active period is going to transpire.

Monday night/Tuesday:
Short wave will eject out of the incoming large scale trough and develop thunderstorms over NE MX and SW TX. Some of these storms will become severe and this activity will move eastward, but likely weaken early Tuesday morning over C TX. Will need to watch for any boundary trying to move into SE TX early Tuesday that would help to focus development Tuesday afternoon.

Tuesday afternoon-Wednesday midday:

Significant short wave disturbance will likely result in widespread thunderstorms, heavy rainfall, and flash flooding.

Departing short wave Tuesday morning will give way to strong SE onshore flow by midday with significant moisture advection on a 50-60kt low level jet across coastal TX. Air mass will become increasingly unstable with current forecast sounding showing CAPE of over 2000 J/kg and LI’s down in the -4 area. Breaks in the overcast will only lead to more destabilization. Strong lift will spread across SW TX by early Tuesday afternoon and expect vigorous thunderstorm formation in NE MX/SW TX which will then move eastward Tuesday night. Severe parameters are maintained all night with a dramatic increase in the low level shear profiles Tuesday night favoring a threat for tornadoes and wind damage. Not sure how much development will occur over the warm sector ahead of what will by this time become a very well defined MCS over the TX coast bend into C TX where severe and excessive rainfall will be ongoing. Certainly could be cells developing in the warm sector with a tornado threat Tuesday evening and all night over SE TX. Severe probabilities upgrade may be required in additional outlooks if the tornado threat looks higher. All severe modes will be possible at this time with wind and tornadoes the greatest.

Other significant concern is going to be excessive rainfall and flash flooding. Well defined MCS will move slowly eastward into highly moist air mass being fed by 50-60kt low level jet Tuesday night/Wednesday morning. Forecast models want to slow down this MCS over coastal TX/SE TX Wednesday morning where favored wind field become parallel to the mean upper level flow…the result will likely be a period of prolonged cell training and cell mergers. Saturated air column in this setup is concerning for high hourly rainfall rates of 1-3 inches per hour and rapid onset flash flood event. HPC has already outlooked much of the region for slight to moderate risk for flash flooding and excessive rainfall.

Widespread rainfall amounts of 3-5 inches appear likely with isolated totals of 6-8 inches especially east of I-45 where cell training appears the greatest threat. 24-hour storm total from 600am Tuesday to 600am Wednesday are very impressive over the region with a solid 2-4 inches likely. Models have been trending southward and southwest with the axis of maximum rainfall the last few days from around Little Rock now toward Toledo Bend…which is concerning as values around the Sabine River in that same 24 hour period could be 6-9 inches.

Rainfall of this magnitude will cause significant rises on area creeks, bayous, and rivers. I am really worried about the Trinity and San Jacinto Basins given basin wide amounts of 3-5 inches is looking likely. However rises on all basins is almost certain given the widespread nature of the event. Urban flash flooding will also be a concern with higher hourly rainfall rates.

Wednesday afternoon-Thursday:
Hopefully the area will get into a break by Wednesday afternoon and Wednesday evening before another strong short wave rotates around the parent upper level storm which by this time will be located over NE MX/SW TX. Strong height falls will force surface low pressure over S TX which will move NE along or offshore of the TX coast. Current track of this feature is just offshore of SE TX coast and then inland over far E TX/W LA on Thursday. The track of this feature will be very important on additional rainfall on Thursday as another significant round of excessive rainfall will focus on the north and eastern side of this feature Thursday. Think our eastern counties could get clipped by this with the majority of the excessive rainfall over the Sabine River valley where another 6 inches could fall on top of the 6-9 inches on Wednesday. If this surface low tracks more across SE TX, then Thursday will be a very bad day across the region with excessive rainfall and flash flooding almost certain.

Friday:
Not done yet! Main upper level low will eject across TX during the day Friday into possibly Saturday. Very cold air aloft will result in an unstable air mass over the region by late morning with showers and thunderstorms developing. Cold air favors a hail threat with these storms. Think moisture will somewhat limited by Friday, but by that time any additional rainfall will likely lead to problems. Should see the main storm system exit to the east by late Friday, but the latest ECMWF is slower once again and lingers the system over the area in Saturday which would keep rain chances going another day.

Tides:
Strong onshore flow will develop later today and continue for the next 48 hours. SE winds of 25-35mph will raise tide levels along the coast and likely result in tidal run-up and minor coastal flooding at high tide on Monday with better potential on Tuesday as wave run-up is maximized. Total water levels may be up around 2.5-3.5 ft by Tuesday afternoon which could cause issues on Bolivar, near Surfside, and on the western side of Galveston Bay at Shoreacres.

[Tireman4]

Houston soundings?

[wxman57]

12z EC says 7-9" across my part of Houston Tue-Thu. Speedo ready...

[wxman57]

Houston soundings?

A good bit of moisture around by Wednesday morning. Here's the URL. Click the RAP, NAM, or GFS then click on the map to get a sounding for that point. You can use the inset map on the right to zoom in on the location and re-draw the sounding. Change the time in the left navigation frame:

http://www.twisterdata.com/

Valid 6am Wed:

[TheProfessor]

The 18z Nam shifted the worse of the severe weather east and south of the metroplex. Locations will probably move around a bit, but it looks like someone in the state might get hit with some intense storms Tuesday.

[TeamPlayersBlue]

That Houston sounding looks nuts.
SREF plume for HOU essentially is 3.6" of rain. There is one outlier of a model that produces 7" of rain.

[TeamPlayersBlue]

Looking at the nino 1-2 region and how it has warmed up, is this likely the reason why late Feb and March is so warm too? The return of my pesky 5H east of Hawaii?

[Ntxw]

Looking at the nino 1-2 region and how it has warmed up, is this likely the reason why late Feb and March is so warm too? The return of my pesky 5H east of Hawaii?

I think it's been warm simply because there is just no real cold anomalous air available much anywhere in the NH. The Nino has pumped a lot of heat into the atmosphere. The slightly warm patterns have overachieved in surface temps while cold patterns underachieved even in good flow. Hopefully the coming Nina can reverse that effect.

[WeatherGuesser]

KTAL is calling for 10-12" in parts of ArkLaTex.

http://www.arklatexhomepage.com/weather ... -this-week

[Ntxw]

I'm surprised flood or flash flood watches haven't yet been posted by the NWS though I'm sure it is forthcoming. Especially I-35 and points east.

DFW will likely challenge the wettest March on record.

[Brent]

Day 2 enhanced is up south of DFW:

SPC hints at the greatest threat down there being mostly overnight

[KatDaddy]

This morning's Houston-Galveston AFD states it well:

...DANGEROUS WEATHER SITUATION DEVELOPING TUESDAY NIGHT INTO WEDNESDAY MORNING…

An upper level low to drop into N MX and then move very slowly E over the week bringing all modes of severe weather and the potential for heavy flooding rains. A Coastal Flood Watch haas been issued for the Upper TX Coast from high tides. In addition, Wind Advisories are in effect the western portion of SE TX. Look for a Flash Flood Watch to be issued tomorrow if not later today. A Flash Flood Watch is already in effect for SW LA. SPC has an enhanced risk area for S Central and SE TX late Tuesday into Wednesday morning.

This has the potential to be a significant weather event for a large portion of TX with widespread heavy flooding rains and night time tornado event across S Central and SE TX Tuesday night into Wednesday morning. Stay weather aware through the week.

[srainhoutx]

Morning briefing from Jeff:

***High impact….potentially dangerous…weather event for SE TX Tuesday-Wednesday***

Impacts listed in order of greatest threat:

· Excessive rainfall / flash flooding

· Tornadoes

· Damaging winds

· Large hail

· Coastal flooding

· Non-thunderstorm winds

Discussion:
Powerful upper level storm system will dig into MX over the next 24 hours while air mass over TX becomes primed for widespread outbreak of severe thunderstorms and flooding rainfall. Lead short wave will eject into TX this evening and erupt thunderstorms on returning Gulf moisture. This short wave leaves behind a low level boundary over SE TX on Tuesday which will help to focus rapid and intense storm develop Tuesday afternoon as next more potent short wave ejects out of the mean trough over MX. Air mass by midday Tuesday will become unstable and strongly sheared with severe parameters looking favorable. Moisture levels surge to 1.85 inches which is near maximum levels for early March with soundings saturated. Excessive rainfall and flash flooding is looking likely Tuesday afternoon –Wednesday.

Tuesday afternoon-Wednesday:
Morning short wave will mainly pass north of our area, but looks like some sort of low level boundary sneaks in and stalls near the coast around noon. Expect a few showers to be ongoing Tuesday morning spreading inland from the Gulf of Mexico. Powerful short wave begins to eject into SW TX around midday with strong height falls and tremendous lift overspreading a very moist and unstable air mass. Appears in short range guidance that surface feature near the coast activates with deep convection as lift increases Tuesday afternoon and spreads northward. These storms could be high precipitation supercells with both excessive rainfall and a tornado threat.

Latest guidance is showing small breaks Tuesday evening before main show arrives from the west between midnight and 600am. Mature MCS with all severe modes and flooding rainfall is likely to cross SE TX during this time period. Wind field continue to intensify Tuesday night with low level shear values peaking Wednesday morning. Cells developing ahead of the main line will have a tornado threat as well as supercells within the main line. Severe threat is certainly tied toward damaging winds and tornadoes

I am becoming increasingly worried about the potential for cell training Tuesday afternoon and evening with any low level boundaries in place over the region followed by rapid increase in widespread activity overnight. Moisture levels are very high and will support high hourly rainfall rates. Will hit the area pretty hard on the QPF with 24-hr totals from noon Tuesday to noon Wednesday of widespread 3-4 inches and isolated amounts up to 6-8 inches. Highest threat is across eastern counties of Liberty, San Jacinto, and Polk, but training potential Tuesday afternoon and evening could bring the potential higher totals back to the SW some.

Flash Flood Watch will be needed today.

Not sure when exactly the rainfall is going to shut off on Wednesday. Position of the upper level low suggest a dry slot will rotate into the region at some point on Wednesday on the backside of the morning activity. Some models show a rapid shut off in rainfall while others linger it into the afternoon and even the evening hours. Thinking currently is to go with the faster ending of the rainfall from west to east as the air mass is worked over…but will have to watch and see how things play out.

Thursday-Friday:
Should be drier on Thursday before main upper level storm moves across the region on Friday. Potential for another round of showers and storms on Friday over the region.

Tides:
Strong onshore flow has developed and will continue with winds of 25-35mph for the next 24-36 hours. This is going to push a lot of water toward the coast and overnight ET storm surge guidance suggest total water levels could be pushing 4.0-4.5 ft by Tuesday afternoon which is near warning levels on the Gulf facing shores and on the west side of Galveston Bay.

Coastal Flood Watch is in effect for Brazoria, Chambers, Harris, and Galveston Counties.

Upgrade to Coastal Flood Warning is likely for overwash of Bolivar on Tuesday.

Winds:
Strong winds will develop today and continue through Tuesday night. Expect sustained speeds of 20-30mph with gust to 40mph. Some models are showing a few gusts of 45mph early Tuesday evening due to very strong gradient

[jasons2k]

It's going to be a very active week with several rounds of heavy rain. Everyone be safe and keep an eye on the sky!

[gboudx]

The Corp of Engineers is releasing water from Lavon, I assume in preparation for the amount of water about to fall into it. It's 8"-10" above pool elevation.

[TexasSam]

It sounds like it's going to be a wild next few day! Be safe everyone. I hope my neighbors newly planted garden is going to be ok.

[wxman57]

12Z Euro has a 10" bullseye over southwest Houston and eastern Ft. Bend County (including Sugar Land), mostly on Wednesday. Much of Harris County with 5-8" Tuesday evening through Wednesday afternoon.

[TeamPlayersBlue]

What are the totals for the latest run of the Euro? GFS had SGR with about 4" of rain. Wed morning it has the LLJ kicking up at 60 MPH. Thats a little scary.

Edit: Got me.