March 2016 - Progressive Changeable Weather To End The Month

[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

Severe Weather Outlook (Tuesday):

[wxman57]

12Z Euro has a 10" bullseye over southwest Houston (my house) and eastern Ft. Bend County, mostly on Wednesday. Much of Harris County with 5-8" Tuesday evening through Wednesday afternoon. Looking likely that much of Houston will see in the 5-8" range. Travel issues likely on Wednesday due to flooded streets. Can't tell precise timing yet.

Here's a graphic I made from the 12Z Euro:

[srainhoutx]

Three day QPF amounts continue to increase across most of SE Texas. Also low level jet has really increased the past hour or so across the Region with 4mb per hour pressure falls noted here in NW Harris County. Just had a wind gust to 41 MPH at the house.

[srainhoutx]

Afternoon updated Excessive Rainfall Outlook from the Weather Prediction Center has expanded the Moderate Risk to include all but the extreme SW zones of SE Texas.

[jasons2k]

Yes, it's looking more like we're going to have some flooding issues to contend with in and around the Houston area.

[jasons2k]

Just got an alert on my iPhone a Flood Watch was issued...

FLOOD WATCH
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
302 PM CST MON MAR 7 2016

TXZ163-164-176>179-195>200-210>214-226-227-235>238-081200-
/O.NEW.KHGX.FF.A.0001.160308T1800Z-160310T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
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-
INCLUDING THE CITIES OF...ALVIN...ANAHUAC...ANGLETON...BAY CITY...
BELLVILLE...BRENHAM...BROOKSHIRE...BRYAN...CALDWELL...CLEVELAND...
COLDSPRING...COLLEGE STATION...COLUMBUS...CONROE...CORRIGAN...
CROCKETT...DAYTON...EAGLE LAKE...EDNA...EL CAMPO...FREEPORT...
FRIENDSWOOD...GALVESTON...GROVETON...HEMPSTEAD...HOUSTON...
HUMBLE...HUNTSVILLE...KATY...LAKE JACKSON...LAKE SOMERVILLE...
LEAGUE CITY...LIBERTY...LIVINGSTON...MADISONVILLE...
MISSOURI CITY...MONT BELVIEU...NAVASOTA...ONALASKA...PALACIOS...
PASADENA...PEARLAND...PIERCE...PRAIRIE VIEW...RICHMOND...
ROSENBERG...SEALY...SHEPHERD...SUGAR LAND...TEXAS CITY...
THE WOODLANDS...TOMBALL...TRINITY...WEIMAR...WHARTON...WILLIS...
WINNIE
302 PM CST MON MAR 7 2016

...FLASH FLOOD WATCH IN EFFECT FROM NOON TUESDAY THROUGH
WEDNESDAY AFTERNOON...

THE NATIONAL WEATHER SERVICE IN HOUSTON/GALVESTON HAS ISSUED A

* FLASH FLOOD WATCH FOR A PORTION OF SOUTHEAST TEXAS...INCLUDING
THE FOLLOWING AUSTIN...BRAZORIA...BRAZOS...BURLESON...
CHAMBERS...COLORADO...FORT BEND...GALVESTON...GRIMES...
HARRIS...HOUSTON...JACKSON...LIBERTY...MADISON...MATAGORDA...
MONTGOMERY...POLK...SAN JACINTO...TRINITY...WALKER...WALLER...
WASHINGTON AND WHARTON.

* FROM NOON TUESDAY THROUGH WEDNESDAY AFTERNOON

* PERIODS OF SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A SLOW-
MOVING STORM SYSTEM ARE EXPECTED TO MOVE ACROSS SOUTHEAST TEXAS
TUESDAY AFTERNOON THROUGH WEDNESDAY AFTERNOON.

* TIMING... HEAVIEST RAINS ARE EXPECTED TUESDAY NIGHT INTO
WEDNESDAY MORNING.

* AMOUNTS... WIDESPREAD RAINFALL AMOUNTS OF 3 TO 7 INCHES ARE
EXPECTED WITH LOCALLY HIGHER AMOUNTS POSSIBLY APPROACHING 10 TO
12 INCHES.

* MAIN THREAT...FLASH FLOODING OF LOW LYING LOCATIONS ESPECIALLY
IN URBAN AREAS WITH POOR DRAINAGE OR RURAL ROADS IN HILLY
TERRAIN CAN BE EXPECTED. FLOODING OF STREAMS... CREEKS... AND
BAYOUS IS LIKELY THROUGH WEDNESDAY. HEAVY RAINFALL MAY CAUSE
SIGNIFICANT TRAVEL IMPACTS DURING THE WEDNESDAY MORNING COMMUTE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.

YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.

&&

[Cromagnum]

10+ inches of rain in our area from that map. Calling hype on this now and bet we see closer to 3-4 inches max. I had to crack up at the east texas weathermen during the last "storm". Telling people to turn their tv up real loud and hide in the closet and they would tell them when it was safe to come out. It didn't even do anything. I don't remember people causing such a ruckus about some rain until the last 10-15 years. They sure didn't do it as a kid.

[tireman4]

Folks, be weather wary. Even if is just "3-4 inches", that can cause problems for some places. Remember, there could be embedded places of 5-7 or even more inches. This has the 'potential" to be a mass rain maker. Stay tuned to your weather outlets and here.

[tireman4]

10+ inches of rain in our area from that map. Calling hype on this now and bet we see closer to 3-4 inches max. I had to crack up at the east texas weathermen during the last "storm". Telling people to turn their tv up real loud and hide in the closet and they would tell them when it was safe to come out. It didn't even do anything. I don't remember people causing such a ruckus about some rain until the last 10-15 years. They sure didn't do it as a kid.

I will say this. I agree with your last statement. Let me add. Houston is MUCH bigger than it was when were kids. Sometimes the drainage systems have not caught up with the urban sprawl. Plus, if you get massive amounts of rain in one area, it will overload even the best of systems. Remember, it always vigilant to be wary of any system. Weather can change on a dime. I did not mean to single you out, but remember, you might get 3-5 inches, I might get 10 inches.

[wxman57]

10 inches or more in parts of Harris County is possible. I'm thinking widespread amounts in the 4-6 inch range Tue-Thu. Peak rainfall in the county could top 10". Wednesday is not going to be a pleasant weather day. Careful on the roadways, there will be flooding.

[unome]

that cell east of Fort Stockton sure got ugly quick

http://www.srh.weather.gov/maf/
http://forecast.weather.gov/wwamap/wwat ... 0statement

[jasons2k]

I have to say, in events past that were 'hyped', there were some known issues or inconsistencies with the models that were seen ahead of time, or models trending drier, dry slotting, weak instability, etc., and these signs were ignored for whatever reason until the bitter end.

In this case, other than some dry slotting that was mentioned yesterday, the trend in this case seems to be wetter with time.

Unless something changes dramatically over the next 24 hours, this system looks like the real deal. I don't say that very often. My $.02.

[srainhoutx]

While we spend a lot of time talking about weather possibility for our Region, rarely do we see parameters coming together in the short range that suggest a myriad of weather worries particularly in early March with such a strong, dynamic and very far South into Mexico. Our intentions are never to hype on this online weather community. Our main goal is to inform and provide the most accurate and reliable information as humanly possible. Stay tuned as I am sure there will be much more information forthcoming tonight and into tomorrow.

[jasons2k]

^^

I honestly don't think I've ever seen a height chart like that in March before.

[jasons2k]

Latest from Jeff:

***High impact….dangerous storm system…heading for SE TX***

Flash Flood Watch issued all counties from noon Tuesday-Wednesday evening

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

Rainfall:
Significant change is required in the expected rainfall amounts for this event…potentially leading to a dangerous flash flood event for E/SE TX. Latest model guidance has continued the trend of shifting the axis of heavy SSW and deeper into SE TX. This is requiring the adjusting upwards of rainfall totals over the next 24-36 hours. Combination of “tremendous” tropical moisture…rising to record levels for early March…massive upper level divergence on the east side of a monster upper level trough…a strong low level jet of 45kts feeding a continuous supply of moisture into a potentially WSW to ENE low level boundary all point to a very high flash flood threat from training strong thunderstorms over SE TX Tuesday evening/overnight.

Widespread Rainfall: 4-6 inches
Isolated Rainfall: 8-10 inches

Note that the amounts listed above are still lower than some guidance including some of the HPC graphics and HGX totals which are pushing isolated totals toward 12 inches. Would certainly not be surprised with 10-12 inches, but the narrow training bands that such totals will fall under I have no confidence of at this time. Will favor areas E of I-45 for maximum totals, but the entire area is under the gun!

Large scale rises on all watersheds are almost certain with this magnitude of rainfall and some will likely exceed their flood stages. If model trends and totals hold into tomorrow morning…we are facing a very serious flood/flash flood threat over this region.

Severe:
All parameters a go for a prolonged severe weather threat from early afternoon Tuesday into Wednesday morning. Low level wind fields really ramp up Tuesday afternoon and evening and suspect a tornado and wind damage threat from high precipitation supercells. Cells will be translating toward the NNE at 35-40mph, but some areas will be hit multiple times in training bands. Large scale upper air forcing arriving across the Rio Grande late Tuesday will force a large MCS to form and track ENE across SC/coastal bend into SE TX Wednesday morning. Will maintain wind damage threat with this line along with a tornado threat (likely lower than Tuesday evening).

Tides:
Tides are already coming up with strong onshore winds and the winds will only increase with strong gradient in place. Expecting 25-35mph with higher gusts Tuesday pushing water into the coast. ET surge showing an impressive 2 ft of surge at Galveston and total water level rise up around 3.5-4.0 ft which is close to causing minor flooding and overwash especially on Bolivar (Hwy 87). Could see some issues on the west side of Galveston Bay also.

Decision Support:

Widespread Rainfall Amounts and Timing:
600am Tues-600pm Tues: 1-2 inches
600pm Tues-600am Wed: 3-5 inches
600am Wed-600pm Wed: 2-4 inches

Flash Flood Guidance (Harris County):
1-hr: 3.4
3-hr: 4.0
6-hr: 4.9

Onset Timing:
Noon-300pm Tuesday

Duration:
Noon Tuesday-600pm Wednesday

Severe:
Tornado: low to moderate
Wind: moderate (60mph+ gusts)
Hail: low (1 inch or larger)


Latest (72 hours rainfall forecast):

http://www.wpc.ncep.noaa.gov/qpf/d13_fi ... 7392196180


Tuesday (Severe Weather Outlook):
http://www.spc.noaa.gov/products/outloo ... 7392234677

[DoctorMu]

San Antonio, Austin, Houston, Victoria, College Station all in the bullseye for severe weather on Tuesday. Tue-Thursday will be nasty, with flooding likely.






DISCUSSION... /ISSUED 402 PM CST MON MAR 7 2016/
AN ACTIVE WEATHER PATTERN IS SETTING UP FOR SOUTHEAST TEXAS AS AN
ANOMALOUSLY STRONG/DEEP UPPER LOW FOR THIS TIME OF YEAR APPROACHES
THE REGION. AFTERNOON WATER VAPOR IMAGERY SHOWS THIS FEATURE
BEGINNING TO TAKE SHAPE OVER SOUTHERN/BAJA CALIFORNIA AND WILL
TRANSLATE DIG SOUTHEAST INTO NORTHERN MEXICO OVER THE NEXT 24 TO
36 HOURS. AS THIS HAPPENS... FAVORABLE UPPER LEVEL SUPPORT
COMBINED WITH EXCEPTIONALLY MOIST LOW LEVEL INFLOW WILL RESULT IN
PERIODS OF SHOWERS AND THUNDERSTORMS CAPABLE OF SEVERE WEATHER AND
HEAVY RAINFALL ACROSS SOUTHEAST TEXAS TUESDAY AFTERNOON THROUGH
WEDNESDAY AFTERNOON.

GENERALLY DRY CONDITIONS ARE EXPECTED TO PERSIST THIS AFTERNOON
AND EVENING... WITH ISOLATED TO SCATTERED SHOWERS DEVELOPING
OVERNIGHT TONIGHT ACROSS THE REGION AS A 45 TO 50 KNOT LOW LEVEL
JET INTENSIFIES ACROSS THE REGION. AS THE UPPER LOW DIGS FARTHER
INTO MEXICO DURING THE DAY ON TUESDAY... INCREASINGLY DIFFLUENT
FLOW ALOFT WILL ALLOW FOR THE FIRST ROUND OF CONVECTION TO GET
GOING TUESDAY AFTERNOON WITH WIDESPREAD SHOWERS AND THUNDERSTORMS
DEVELOPING ACROSS THE REGION.

WITH MLCAPE VALUES APPROACHING 1000-2000 J/KG... 0-6 BULK SHEAR
VALUES AROUND 40-50 KNOTS... AND 0-1 KM SHEAR VALUES EXCEEDING 25
KNOTS TUESDAY AFTERNOON AND EVENING... STRONG TO SEVERE
THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ACROSS MOST OF THE
REGION. ISOLATED TORNADOES AND DAMAGING WIND WILL BE THE PRIMARY
THREATS WITH THIS ACTIVITY... WITH THE AMOUNT OF WIND ENERGY
ASSOCIATED WITH THIS STORM SYSTEM ALLOWING THE TORNADO AND
DAMAGING WIND THREAT TO PERSIST WITH ANY THUNDERSTORM THAT
DEVELOPS WELL INTO THE EVENING AND OVERNIGHT HOURS AS THE LOW
LEVEL JET REINTENSIFIES. HOWEVER... AN UPPER LEVEL SPEED MINIMA
MOVING ACROSS THE REGION AROUND MIDNIGHT WEDNESDAY MIGHT BE ENOUGH
TO PROVIDE A BRIEF BREAK IN RAIN CHANCES LATE TUESDAY. THIS WILL
QUICKLY CHANGE AS THE UPPER LOW DRAWS CLOSER EARLY WEDNESDAY
MORNING... WITH AN ASSOCIATED THUNDERSTORM COMPLEX BLOSSOMING
ACROSS SOUTH CENTRAL TEXAS AND MOVING EASTWARD THROUGH THE
REMAINDER OF THE DAY WEDNESDAY.

ADDITIONALLY... A THREAT FOR HEAVY RAIN WILL EXIST ACROSS THE
REGION DURING THIS TIME AND PEAK LATE TUESDAY INTO WEDNESDAY
MORNING COINCIDENT WITH THE HIGHEST ATMOSPHERIC MOISTURE LEVELS. WHILE
ANTECEDENT CONDITIONS ARE NOT THE MOST SUPPORTIVE FOR RUNOFF
LEADING TO FLASH FLOODING GIVEN THE RECENT DRY SPELL THE REGION
HAS BEEN UNDER /HOUSTON INTERCONTINENTAL IS OVER 3 INCHES BELOW
NORMAL FOR RAINFALL FOR THE YEAR SO FAR/... FORECAST SOUNDINGS
SHOW PRECIPITABLE WATER VALUES CLIMBING TO 1.7 TO ALMOST 1.9
INCHES WEDNESDAY MORNING. THESE VALUES ARE NEAR RECORD LEVELS
WHEN COMPARED WITH SOUNDING CLIMATOLOGY FOR CORPUS CHRISTI AND
LAKE CHARLES. ADDITIONALLY... STORM MOTION OF INDIVIDUAL CELLS IS
EXPECTED TO BE VERY QUICK /CELLS MOVING SOUTH TO NORTH AROUND 35
TO 40 KNOTS/ BUT GENERALLY UNIDIRECTIONAL SHEAR PROFILES DURING
THIS TIME WILL ENCOURAGE STORMS TO TRAIN ACROSS THE SAME AREA.

AS A RESULT... HAVE ISSUED A FLASH FLOOD WATCH FOR ALL OF
SOUTHEAST TEXAS BEGINNING NOON TUESDAY AND LASTING THROUGH
WEDNESDAY AFTERNOON. SREF PLUME MEANS SHOW RAIN TOTALS GENERALLY
AROUND 5 INCHES ACROSS MUCH OF THE REGION... BUT LOCAL FLASH FLOOD
GUIDANCE OFFERS SOME SUPPORT FOR ISOLATED HIGHER AMOUNTS THAT
OUTLIERS ARE ADVERTISING /AROUND 10 INCHES/ GIVEN THE ANTICIPATED
TRAINING... INSTABILITY... AND HIGH AVAILABLE ATMOSPHERIC
MOISTURE. ACCORDINGLY... WIDESPREAD RAIN TOTALS OF 3 TO 7 INCHES
WILL BE POSSIBLE WITH LOCALLY HIGHER AMOUNTS OF 10 TO 12 INCHES.
GIVEN THE ANTICIPATED TIMING OF THIS COMPLEX... TRAVEL IMPACTS
WILL BE POSSIBLE ACROSS MUCH OF THE REGION WEDNESDAY MORNING.

SUBTLE DISTURBANCES TRANSLATING ACROSS THE REGION IN THE
SOUTHERLY FLOW ALOFT AHEAD OF THE UPPER LOW WILL RESULT IN PERIODS
OF SHOWERS AND THUNDERSTORMS CONTINUING ACROSS THE REGION
WEDNESDAY EVENING INTO THURSDAY MORNING... BUT THE BEST
INFLOW/MOISTURE SHIFTS EAST OF THE REGION AND WILL HELP LIMIT THE
HEAVY RAIN THREAT DURING THIS TIME. MEDIUM RANGE GUIDANCE
CONTINUES TO STRUGGLE WITH CONSISTENCY GIVEN THE PLACEMENT/TRACK
OF THE UPPER LOW... BUT WITH THIS FEATURE IN THE VICINITY OF THE
REGION THROUGH THE END OF THE WEEK HAVE MAINTAINED SHOWER AND
THUNDERSTORM CHANCES IN THE FORECAST THROUGH SATURDAY.

[srainhoutx]

Cautiously will post a 00Z NAM sounding in NW Harris County.

[jeff]

10 inches or more in parts of Harris County is possible. I'm thinking widespread amounts in the 4-6 inch range Tue-Thu. Peak rainfall in the county could top 10". Wednesday is not going to be a pleasant weather day. Careful on the roadways, there will be flooding.

Rainfall of that magnitude in Harris County will cause major house flooding. Memorial Day was 8 inches in 3 hours with between 4000-8000 homes flooded. These kind of rainfall totals are no joke.

[TexasBreeze]

Let alone the severe weather parameters, the forecast pw of 1.92" in that NAM sounding above is deep tropical (for March standards!)