Texas Severe Weather Potential for 4/28 and 4/29

[Extremeweatherguy]

Also...the NWS in Houston has upped the rain chances for tonight/tomorrow to 100%!

[Extremeweatherguy]

NWS morning discussion:

000
FXUS64 KHGX 281137
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
637 AM CDT FRI APR 28 2006

.DISCUSSION...
WARM AND BREEZY AFTERNOON IN THE WORKS AS TROPICAL MOISTURE IN
THE PACIFIC TAP ARCS IN ACROSS NORTHERN MEXICO AND SOUTH TEXAS AS
LOW LEVEL FLOW STRENGTHENS IN RESPONSE TO THE UPPER LOW NEAR THE
NM/AZ BORDER MOVING OUT INTO THE SOUTHERN PLAINS. THIS SYSTEM IS
GOING TO BRING A ROUND OF THUNDERSTORMS TO THE AREA TONIGHT AND
EARLY SATURDAY. SOME OF THE PARAMETERS THAT SHOULD BE IN PLACE
HERE TONIGHT AS THE ORGANIZING MCS MOVES OUT OF THE HILL
COUNTRY...LI -4 TO -7...CAPE 1000-2000 J/KG...CINH -80 TO 0...EHI
1-3.5...PW 1.7 TO 2.1"...LLJ 45 TO 60 KTS...0-3 KM HELICITY 250-450.
INCREASING DIFFLUENCE ALOFT AS ANTICYCLONIC FLOW OVERHEAD SHIFTS
EAST AND CYCLONIC FLOW INCREASES WITH JET INCREASING TO 100-110
KNOTS. MODELS INDICATING THAT CINH DROPPING (THOUGH S/W THAT MOVED
THROUGH EARLY THIS MORNING IMPLIES INCREASING SUBSIDENCE) THIS
AFTERNOON AND ISOLATED TO SCATTERED THUNDERSTORMS COULD BE
POSSIBLE ACROSS THE REGION. BEST RAIN CHANCES LOOK TO BE AROUND
06Z WESTERN ZONES AND 12-15Z EASTERN. FOR WHAT IT IS
WORTH...MODELS APPEAR CONSISTENT IN TRACKING THE MCS EAST AT 22-
25 KNOTS BUT WITH 50-60 KNOT LLJ TO THE EAST AND 40-50 KNOT
DRY/COOL INFLOW INTO THE BACK OF THE MCS IT COULD MOVE FASTER SO
MUCH OF THE TIMING OF THE FORECAST WILL BE IN RELATION TO WHERE
THE MCS FIRST SETS UP AT ALONG THE DRYLINE. LOOKS LIKE WE SHOULD
HAVE A LINEAR MCS ENTER THE WESTERN COUNTIES WITH A LEWP DEVELOP
OVER THE WESTERN/SOUTHWESTERN ZONES AND TRACK EAST. STORMS SHOULD
BE MORE THAN CAPABLE OF DAMAGING WINDS...AND GIVEN THE
AFOREMENTIONED PARAMETERS CANNOT RULE OUT TORNADOES ALONG WITH A
GOOD WIDESPREAD 1/2 TO 1 INCH OF RAIN. IN THE EVENT THAT ISOLATED
STORMS DEVELOP OUT AHEAD OF THE MCS THEN SEVERE WEATHER POSSIBLE
BUT NOT VERY CONFIDENT ATTM OF THIS OCCURRENCE. THE SYSTEM MOVES
OUT OF THE AREA 15-18Z AND WINDS SWING TO THE WEST. THE WEAK
PACIFIC FRONT SHOULD MOVE IN AFTER 18Z BUT MOISTURE SHOULD HAVE
BEEN SCOURED OUT BY MCS. FRONT WASHES OUT VERY QUICKLY AND
SOUTHEASTERLY FLOW PICKING BACK UP SUNDAY AFTERNOON. (CURRENT
AFTERNOON TEMPS IN THE MID TO UPPER 80S MAY BE TOO LOW) ANOTHER
COLD FRONT SETTLING SOUTH TUESDAY BRING A SLIGHT CHANCE TO THE
NORTHERN 1/2 OF THE AREA WITH STORMS DRIFTING OFF THE STALLED
FRONT OVER N TX IN WNW/NW FLOW ALOFT. THE FRONTAL BOUNDARY LINGERS
OVER N TX TUESDAY THROUGH THURSDAY AS LOW OVER THE CENTRAL US
LIFTS OUT TO THE NORTHEAST AND ANOTHER SYSTEM DROPS DOWN OUT OF
MONTANA INTO THE WEAK UPPER TROUGH AXIS. MAY GET ANOTHER COLD
FRONT TO THE COAST FRIDAY...BUT THAT IS A LOW CONFIDENCE FORECAST.

[TexasStooge]

Rain chances here in the DFW area are 100% for tonight, and yes we're gonna have some severe weather as well.

[jeff]

***Significant threat for severe weather tonight.***

Potential for a long lived derecho (large scale damaging wind event) across almost all of TX.

Discussion:

Parameters coming together for an extensive round of severe weather. Potent upper low located near the AZ/NM border will eject into the southern plains this evening. Low level tropical air mass is urging northward into SE and C TX on an increasing low level jet. Surface dewpoints will climb into the low 70's by afternoon. W TX dryline will sharpen in response to falling surface pressures and increasing low level moisture over SW TX. Surface heating over the higher terrain of NE Mexico and the Trans Pecos region of W TX will ignite severe convection once lift from the upper low overspreads the dryline. Shear profiles are impressive with a 100kt mid level jet crashing through northern Mexico. Storms will quickly congeal and grow upscale into a large MCS and race eastward across the state.

Local Discussion/Timing/Atmo. Parameters:

Local air mass will be primed for severe weather by late afternoon. CAPE values exceed 1500 J/kg with LI's of -4 to -7. Capping will weaken and nearly erode by early evening with forecast soundings showing -40 to -60 J/kg of cap left (0 J/kg would be an eroded cap). Low level jet increases to near 45kts this evening and as high as 55kts overnight. PWS rise to an impressive 1.9-2.1 inches and low level shear values in the 0-3km range increase to nearly 350 m^2/s^2 (ouch). Upper level divergence greatly increases after dark along with a 120kt mid level jet max plowing into the region from the WSW.

Severe MCS will be moving out of SW and C TX by 1000pm and approaching the I-35 corridor by midnight. Forecast models show 50-60kts of low level inflow over SE TX and nearly 45kts of cold dry inflow into the back of the MCS. Given such wind energy being depicted in the models will not bode well for the area with respect to wind damage.

MCS should enter out western counties around 200am and accelerate ESE and E into favorable low level inflow pattern. Line echo wave pattern along with multiple bow echo formations are likely, producing significant and possibly widespread wind damage. Intense line should reach metro Houston between 300am and 600am and exit the eastern counties and coast around 900am. Given a forecasted 45-50kt of back inflow into the MCS may indicate a long period of high winds associated with an extreme meso/wake low formation within the MCS. High winds may continue for several hours. Leading edge gust front winds may exceed 70mph with forward storm propagation of 40-50mph.

Pattern is favorable for strong bowing segments along with notches along the line where weak tornadoes will be possible (similar to Fort Bend Co. tornado last Friday).

Given the expected widespread nature of the event...future outlooks by SPC may upgrade the area to a moderate risk. I expect numerous watchboxes by early evening with a plethora of weather warnings overnight. Such weather events can be exceptionally dangerous at night when persons are sleeping and are unaware of the approaching threat. Residents with NOAA weather radios should place them into the ALERT mode before going to sleep to receive critical warning information for your county.

[Extremeweatherguy]

wow! A derecho and wake low event all in one! If this plays out, we could see some serious damage around the area. I will have to watch the situation closely tonight and take cover at first sign of trouble. I just hope everyone will be ok. The thing I am really worried about now is power outages. 70+mph gusts would knock out our power for awhile.

[Johnny]

Hopefully Jeff's scenario does not play out for us here in Southeast, Texas. If it does play out then it like we are in for one hell of a ride. Very interesting night ahead. The wind should effect my tomatoes because I have cages around them. Now my corn and potatoes, they'd take a severe beating.

[jasons2k]

Wow, this is getting interesting...almost too interesting.

[CrazyC83]

Wow! This has jumped like crazy! It seems that indeed it will be a derecho/large hail event with some tornadoes mixed in.

[KatDaddy]

This could be a very dangerous and scary event overnight. Eveyone should keep abreast of the weather through the night.

[TexasStooge]

It's probably gonna be a rerun from last week for North Texas.

[Yankeegirl]

I hate it when all of this has to happen at night... I have a weather radio, so I guess I willl leave it plugged in near the bed tonight... and I should get the candles ready too... Its going to be a long night.. Its already overcast here, looks like it wants to rain...

[jasons2k]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1140 AM CDT FRI APR 28 2006

.DISCUSSION...
DEEP SOUTHEASTERLY FLOW IN PLACE ACROSS SE TX THIS MORNING. SFC
DEWPOINTS HAVE INCREASED TO THE UPPER 60S/LOWER 70S AND PWS HAVE
INCREASED TO AROUND 1.5 INCHES. 12Z LCH/CRP SOUNDINGS AND ACARS
SOUNDING FROM IAH SHOW STRONG CAPPING IN PLACE OVER THE AREA WHICH
WILL PRECLUDE ANY THUNDER FOR THIS AFTN. HOWEVER...WITH THE DEEP
MOISTURE IN PLACE...STILL THINK WE WILL SEE SOME SCATTERED -SHRA
FORM UNDER THE CAP AND WILL KEEP THE SLIGHT CHANCE/CHANCE POPS
GOING. TEMPS HAVE ALREADY WARMED TO THE 70S TO NEAR 80 SO WILL
KEEP HIGHS IN THE LOW/MID 80S GOING FOR THIS AFTN DESPITE THE
MOSTLY CLOUDY SKIES.

WATER VAPOR IMAGERY SHOWS STRONG UPPER LOW OVER SOUTHEASTERN
ARIZONA WHILE SURFACE ANALYSIS SHOWS DRYLINE EXTENDING FROM
SOUTHEAST NEW MEXICO TO THE BIG BEND REGION. 12Z NAM/GFS ARE
TRENDING SLOWER WITH THIS SYSTEM...INDICATING THIS MAY BE MORE OF
A SATURDAY MORNING RATHER THAN OVERNIGHT EVENT. FOR NOW WILL
LOWER POPS FOR THE EVENING HOURS AND REMOVE SEVERE THREAT BEFORE
MIDNIGHT. MAY NEED SOME ADDITIONAL ADJUSTMENTS TO POPS/TIMING FOR
AFTERNOON PACKAGE.

[Portastorm]

Weather starting to get active here in south central Texas. Radar lighting up a little more and some scattered storms are starting to pop ... and I know the main event won't be until later this evening.

Looks like we'll get hammered between 10 pm-midnight. Texans, let's all stay in touch as they could be a wild weather night!

[jasons2k]

Wow, already some warnings going up in the Abilene area.

[Johnny]

I changed the title of this thread to include the entire state of Texas.

I'll be reporting my conditions when the time arriives. I hope everyone else does the same.

[jasons2k]

I changed the title of this thread to include the entire state of Texas.

I'll be reporting my conditions when the time arriives. I hope everyone else does the same.

I'll be online to do the same. Should be an interesting night and Sat. AM. Good luck to all my fellow Texan friends out there!

[CrazyC83]

This event has me a bit confused. Will it be primarily a tornado event or a derecho event?

[Yankeegirl]

I will be here too !!! I will prolly be in the CHAT room, you all need to stop by and visit!!!

[Johnny]

From what I understand it will be more of severe squall line, possibly derecho event. Isolated tornadoes will be possible throughout the squall line.

[CrazyC83]

NOT AN OFFICIAL FORECAST - just my prediction.

All and all, I don't have a great deal of confidence and I see a fair bit of uncertainty in this event. As a result, I cannot go above Level 3 with the risk at this moment.