SE TX weather thread #4 - Severe weather Fri/Sat

[Extremeweatherguy]

0Z GFS is coming in, and it still looks chilly...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _138.shtml
^^Cold front reaching TX by next Wednesday afternoon (Notice the 1044mb high up in the NW United States which will drive the air due south), Behind the front temps. drop off quite rapidly.^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _162.shtml
^^A 1051mb+ high (which is only slightly weaker than the Dec. 1989 record smashing high pressure) helps to push cold air south into Texas on Thursday. By Midday, 850mb temps. in the panhandle are below -9C and the 0C 850mb line has reached central TX. In Houston, a line of storms will have come through and the front will be switching winds to a gusty northerly direction. A few snowflakes will be possible in north TX as temps. there fall to near freezing. In Houston, our temps. should fall into the 30s and 40s behind the front (During Mid Afternoon!!!).^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _180.shtml
^^Friday morning (Dec. 1st) features a widespread freeze.^^

However, though this is still cold, I believe that it is still a bit underdone. With a high that strong, the cold air would dig a little further south than shown and would not be shoved off east as quickly. A 1051mb high is just too incredibly strong to allow that to happen as quickly as the model shows. The model seems to still be having a few minor problems. None the less, it IS still showing the coldest air of the season..and possibly the year (and is colder than the 18Z run).

**I just took a closer look at the 18Z on accuweather pro and it does still indicate the chance of a snow flurry, sleet pellet or brief area of freezing rain early on Friday morning. This winter weather trend has been with us for most of the last many model runs and is interesting to see it is still showing this. Also, the more in-depth look showed that IAH is forecast by the GFS to reach 29F next Friday morning and 25F next Saturday morning. If it did so, those would be the coldest numbers we have seen all year (including last winter)! Brrr...**

[Extremeweatherguy]

Houston AFD:

DISCUSSION...
DENSE FOG HAS BEEN SLOWER TO DEVELOP THAN WAS PREVIOUSLY
THOUGHT...LIKELY CULPRIT IS THE WIND BEING SLIGHTLY STRONGER
AND THIS IN TURN AIDING IN DEVELOPMENT OF CLOUDS VERSUS FOG.
WILL CONTINUE TO MENTION AREAS OF FOG IN THE ZFP/GRIDS BUT NOT
EXPECTING THE MORE WIDESPREAD DENSE FOG.

FORECAST NOT CHANGED MUCH...STILL EXPECTING A PERSISTENT RETURN
FLOW AS A LARGE STORM COMPLEX DEVELOPS MONDAY/TUESDAY OVER THE
CENTRAL PLAINS/FOOTHILLS. RAIN CHANCES INCREASE MONDAY WITH
SLIGHT CHANCE OFFSHORE INCREASING TO CHANCE INLAND TUESDAY. NOT
WILLING TO GET SPECIFIC YET AS THE GFS SHOWS A SURGE OF DEEPER
MOISTURE COMING INLAND AND I CANT FIND ANY INDICATIONS OF IT YET
ON SATELLITE...STILL TO FAR OUT IN TIME. VERY COLD AIR TO SPILL
SOUTH FROM NORTHERN CANADA AND SHOULD COME ROARING THROUGH HERE
WEDNESDAY NIGHT/EARLY THURSDAY MORNING. ECMWF STILL THE MODEL OF
CHOICE...GFS IS SLOW DRIVING THE FRONT SOUTH (IT HAS ALSO BEEN
THE MOST INCONSISTENT OF THE TWO MODELS ON TIMING).

ABOVE NORMAL TEMPERATURES WILL BE THE NORM...MIN-T 10-17 ABOVE AND
MAX-T 5-10. POST FROPA...TEMPERATURES SHOULD RUN AT LEAST 10
DEGREES BELOW NORMAL AND BE BREEZY/WINDY.

[Extremeweatherguy]

The following is also posted in the "blue norther" thread:

wow! The European model has 850mb temps. over Houston down to 28F by the EVENING of Thursday November 30th! That makes me wonder how cold it brings the city to being overnight! With perfect radiational cooling a hard freeze would be likely! Brrr...

It also really dries out the upper atmosphere at that point with humidities at 850mb and 700mb down below 5%!

The 6Z GFS is also cold and shows the potential for 3 freezing nights in Houston, with two of those nights possibly featuring a hard freeze (it also doesn't dry us out as quickly and shows a chance of a wintery mix Fri. morning).

[double D]

Although the cold doesn't look to hang around for a long time, it does stay with us for abut 3 days. That is a long time for us down in south and southeast Texas.

To bad that moisture will be scoured out, it sure would have been nice to start off December with a little white stuff.

[Extremeweatherguy]

Although the cold doesn't look to hang around for a long time, it does stay with us for abut 3 days. That is a long time for us down in south and southeast Texas.

To bad that moisture will be scoured out, it sure would have been nice to start off December with a little white stuff.

the GFS doesn't dry the atmosphere out as quickly. The 6Z GFS is showing a mix of rain, sleet, frz. rain and snow around our area on Friday morning.

[JenBayles]

And what the GFS giveth, the GFS usually taketh away.

[Extremeweatherguy]

And what the GFS giveth, the GFS usually taketh away.

usually it does, but this time it has had the trend of a little bit of wintery precip. for many runs now. Hopefully this trend keeps up. Either way though it will be COLD! JB this morning is saying Thursday night in the I-10 corridor will be between 26-32F with wind!

Nevermind: The 12Z run of the GFS now takes away the winter precipitation on Friday morning. Too bad. Hopefully it replaces it later on..

[Extremeweatherguy]

Houston's current low max of 51F on December first will likely be shattered with this cold snap, also the record lows of 26F and 28F on the first and the second will likely be in jeopardy. This very well could be the coldest ever early December arctic blast for SE Texas.

[Johnny]

I sure appreciate you keeping us abreast of what the models are saying EWG. I'm going to Wimberley (the hill country) which is about 45 miles south of Austin from Nove 30th through December 4th. I'm guessing it should even be a bit colder than Houston during this time period? Are the models showing any frozen precip for this area? Man, that would be something...even if it's just some good sleet.

[Extremeweatherguy]

I sure appreciate you keeping us abreast of what the models are saying EWG. I'm going to Wimberley (the hill country) which is about 45 miles south of Austin from Nove 30th through December 4th. I'm guessing it should even be a bit colder than Houston during this time period? Are the models showing any frozen precip for this area? Man, that would be something...even if it's just some good sleet.

the 12Z GFS is not showing winter precip. there right now, but it could be a bit colder there than in Houston. However, the models are still seeming to have a few problems, so I would not rule out some winter precip. for the state just yet. Lots to watch in the coming days..

[Extremeweatherguy]

I just posted this in the "blue norther" thread:

the cold trend continues on the GFS. The 12Z run still looks VERY cold (and it is actually a little faster too. The front reaches us earlier than on the 6Z run, and is more in line with the EURO.):

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_138m.gif
^^Early Thursday morning the front should be sweeping through with severe weather. Notice the GFS also still paints a 1050+mb high! Temperatures quickly drop below 50F behind the front for all of Texas and by by about 12-1am Thursday the panhandle and parts of north Texas should be below freezing.^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_144m.gif
^^By about daybreak Thursday all of North Texas is below freezing and SE Texas is in the 30s and 40s with wind (1053mb+ high)^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_150m.gif
^^Temperatures still in the 30s and 40s by mid afternoon Thursday^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_162m.gif
^^By about 12am (midnight) Friday morning, most of the northern 2/3rds of Texas is below freezing with breezy winds still along the coast (low windchills). 850mb temps. fall below freezing all the way down to Brownsville. The high pressure to our west is still a respectable 1044-1046mb at this point.^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_168m.gif
^^Most of the state of TX is below freezing by daybreak Friday morning. Unlike earlier runs, there is now no winter precipitation in the state though. ^^

http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_174m.gif
^^Fri. afternoon should stay below 50F. However, I think it is way too warm still. The 1053mb+ high seems to have weakened unrealistically fast (all the way down to 1034mb).^^

After hour 174, however, the model goes crazy, moves the cold air out way too quick, weakens the strong high unrealistically and warms us up way too rapidly. The GFS is still having a few problems it seems. The above guidance is also still likely a bit too warm. However, it does still indicate the same general trend of CHILLY weather to end next week.

[Johnny]

A saw that you just posted that in the 'winter weather' thread. Very good analysis EWG. Keep 'em coming.

[Yankeegirl]

Well after looking at some weather sites, it looks as if the NWS is getting onboard to at least some moderately chilly weather, they have lowered their high from 62 yesterday to 59 today... I did look at the accuweather site, and they arent showing anything to write home about... they still have highs in the 60's for the middle part of next week, the NWS actually has lower temps forecasted then they do!! Which is an oddity all in itself... SO as for my thoughts, I think we are going to get some colder weather later on by mid week, but how cold, Im not sure... Guess we are going to have to wait till some more model runs come out and give it a few days... I am going to keep my fingers crossed for cold though....

[Extremeweatherguy]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
232 PM CST FRI NOV 24 2006

.DISCUSSION...
DEVELOPING PATTERN CHANGE ALOFT SPELLS A CHANGE IN OUR WEATHER OVER
THE NEXT SEVERAL DAYS AS WE WAIT FOR OUR NEXT COLD FRONT. AS THE SOUTHWEST
FLOW ALOFT BEGINS TO STRENGTHEN...SOUTHEAST TEXAS WILL SEE INCREASING
MID/UPPER LEVEL MOISTURE. AT THE SURFACE...OUR AREA WILL REMAIN ON THE
EDGE OF A SOUTHWEST TO NORTHEAST ORIENTED HIGH CENTERED ALONG THE U.S.
EAST COAST THROUGH THE UPCOMING WEEKEND. PER WATER VAPOR IMAGERY...THE
GULF OF MEXICO REMAINS VERY DRY...AND IT WILL TAKE SEVERAL DAYS OF SOUTH
TO SOUTHEAST SURFACE WINDS IN COMBINATION WITH DEEPENING MOISTURE ALOFT
AND A STRENGTHENING SUBTROPICAL JETSTREAM TO GET RAIN BACK INTO OUR
FORECAST. THIS SHOULD HAPPEN AS EARLY AS SUNDAY NIGHT OFFSHORE AND MONDAY
INLAND. THE CURRENT FORECAST PACKAGE HAS LOW END CHANCE POPS DURING
THE DAY AND SLIGHT CHANCE POPS AT NIGHT MONDAY THROUGH WEDNESDAY. WILL
KEEP THESE NUMBERS THE SAME FOR NOW DUE TO THE INABILITY TO TIME ANY
UPPER LEVELS IMPULSES THIS FAR OUT. ABOVE NORMAL TEMPERATURES WILL CONTINUE
THROUGH WEDNESDAY WITH STEADILY INCREASING OVERNIGHT LOWS (FROM THE
50S INTO THE 60S) AND NEAR STEADY AFTERNOON HIGHS (IN THE 70S). A STRONG
COLD FRONT ALONG WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS WILL
THEN SWEEP THROUGH SOUTHEAST TEXAS WEDNESDAY NIGHT AND VERY EARLY THURSDAY
MORNING. EXPECT RAPID CLEARING BEHIND THE FRONT. THE POST FRONTAL AIRMASS
WILL BE COLD...PROBABLY THE COLDEST SO FAR THIS WINTER SEASON....AND
IT WILL BE BREEZY TOO AS STRONG SURFACE HIGH PRESSURE BEGINS TO BUILD
IN BEHIND THE FRONT. RIGHT NOW...IT LOOKS LIKE WE CLOSE OUT NEXT WEEK
AND START DECEMBER ON THE COLD SIDE. FRIDAY NIGHT LOOKS TO BE THE COLDEST
NIGHT WITH SURFACE HIGH PRESSURE ALMOST DIRECTLY OVERHEAD.

I think the NWS forecast numbers are still too high though. IMO, they need to be lowered by another 10F for the Thursday and Friday time frame.

[double D]

000
FXUS64 KEWX 242110
AFDEWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
310 PM CST FRI NOV 24 2006

.DISCUSSION...
ABOVE NORMAL AFTERNOON HIGHS WILL CONTINUE THROUGH THE REST OF THE
HOLIDAY WEEKEND AND INTO MID-WEEK. ANOTHER ROUND OF PATCHY FOG
WITH EMBEDDED DENSE FOG IS ON TAP FOR SATURDAY MORNING ACROSS THE
EASTERN TWO-THIRDS OF THE CWA. A DENSE FOG ADVISORY MAY BE
NECESSARY, PARTICULARLY ALONG AND SOUTHEAST OF I-35. AS THE UPPER
TROUGH CONTINUES TO DEVELOP OUT TO THE WEST, PRESSURE GRADIENTS
WILL TIGHTEN, CREATING BREEZY CONDITIONS FOR THE NEXT SEVERAL
DAYS. LOW LEVEL MOISTURE WILL ALSO BE ON THE INCREASE...BUT WILL
NOT BE ENOUGH TO GENERATE ANY CHANCES FOR RAIN THROUGH THE
BEGINNING OF THE WEEK. THE ADDITIONAL MOISTURE WILL RESULT IN
GREATER CLOUD COVERAGE OVERNIGHT, LIMITING MORNING LOWS TO THE 50S
AND 60S THROUGH WEDNESDAY.

MODELS ARE BEGINNING TO SHOW MORE CONSISTENCY WITH THE TIMING OF
THE STRONG COLD FRONT FOR NEXT WEEK. FOR NOW, CONTINUING WITH A
FROPA AFTER WEDNESDAY`S MAX HIGH. STRONG NORTHERLY WINDS WILL PUSH
IN BEHIND THE FRONT...LEADING TO A VERY DRY AND WINDY THURSDAY. AS
THE ARCTIC AIRMASS TAKES HOLD BEHIND THE FRONT, EXPECT TEMPERATURES
TO BE 5-10 DEGREES BELOW EARLY DECEMBER NORMALS. WILL LIKELY
[b]SEE WIDESPREAD SUB-FREEZING TEMPERATURES FRIDAY AND SATURDAY]MORNINGS.

Somehow i think it will be more like 10-20 degrees below normal at least. How can you have widespread sub-freezing temperatures with 5-10 degrees below normal?

[JenBayles]

You know, I really have to thank you Extreme for all the analysis. If I relied on the NWS, I wouldn't have a clue!

If this cold snap actually verifies, I'm just glad I'll have the chimney repairs done by then and the wood pile restocked. With Maggie the Puppy Pie (her Pieness on Her Throne) on one side, the Chica Pet on my feet, and Dave on the other side at night, at least I stay pretty cozy on a cold winter's night.

[JenBayles]

Seems to me like the NWS has been bearish on the last several systems until the last possible minute. Is it just me?

[Extremeweatherguy]

Seems to me like the NWS has been bearish on the last several systems until the last possible minute. Is it just me?

no, it isn't just you. They tend to do that a lot. They like to play it safe beyond day 4. If the models look the same by Sunday though, then expect to see their forecast numbers really start to tumble.

Victoria and Austin are forecasting highs near 50F for Thursday, and eventually I think Houston will follow suit (though I think the temperatures will likely fall through the day into the 40s).

[jeff]

Significant upper air pattern amplification will result in a strong arctic air intrusion into the US next week.

Bone dry air mass will gradually moisten over the next 48-72 hours with a chance of rain returning by Monday and Tuesday. A powerful polar jet stream will begin to dig a deepening trough over the Rockies by early next week with the trough moving eastward into the plains around the middle of the week. Buckling of the upper air pattern will result in the dislodging of a very cold arctic air mass over NW Canada and the Yukon of Canada with temps. this morning ranging from -35 to -45 below zero. Very cold and dense air mass should reach the US border by early Monday and surge southward along the front range of the Rockies Tuesday reaching TX on Wednesday.

850mb temps tumble to -3C by late 11/30 over SE TX as strong arctic boundary blasts into the Gulf of Mexico. Massive 1051mb arctic high pressure cell will produce a strong pressure gradient over the area and NW winds will howl with gale conditions along the coast and offshore Wednesday night late and Thursday. Temps. will drop 25-30 degrees with the frontal passage and struggle to get out of the 40's/50's on 11/30 under very strong cold air advection regime. Widespread killing freeze appears likely 11/30 and 12/1 as skies clear out and winds go calm with record lows of 26 and 28 appearing in jeopardy.

Given the intensity of this air mass coupled with the favorable upper air pattern delivery, current guidance may be way too warm with highs and lows for the end of next week.

At this time I will not entertain the idea of frozen or freezing precip. in the post frontal air mass Thursday morning per the 06Z run of the GFS. GFS is likely too fast with the onset of freezing temps. this far south, and the 850mb and 700mb RH drop quite low by the time the air column is frozen. My only concern is the 250mb jet max located over SW TX late on 11/30 and early on 12/1 which could generate mid level lift increasing clouds and possibly saving the area from a hard freeze.

[Extremeweatherguy]

Thanks for the update Jeff! Your professional input in greatly appreciated!