Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 6

[bubba hotep]

From Steve McCauley in dfw this afternoon:

The latest data now starts the precip in the Metroplex a little earlier when we are still very close to freezing, so a wintry mix is looking more possible not just for the western areas of north Texas but for the Metroplex as well. It will turn to all rain Friday.

18z GFS came in faster and a bit more south with the S/W kicking out than 12z, if we could get it faster and more south then we could be back in the game.

Over the past few years I've seen a couple of systems look good in the long range, disappear in the medium range, and then come back strong in the 4th quarter and deliver. Not calling for that but it's always a possibility.

[Srain]

Morning briefing from Jeff:

 

Arctic  air mass heading for TX with another wet storm system Wed-Sat.

 

Big changes on the way this morning with arctic boundary surging through KS into northern OK. Upstream temperatures over NW KS are in the 1’s with the arctic boundary being driven by a massive 1055mb high pressure cell dropping out of NW Canada. Boundary will plow southward today especially across west TX as is common with such air masses and likely push into NE MX before reaching Houston as the cold dense air dams against the Rocky Mountains. Model guidance does not have a good handle on the incoming cold as is usually the case with shallow and very cold arctic fronts. Almost all the guidance is too warm and once again will need to significantly undercut the guidance output to match what in reality will likely occur.

 

Arctic boundary will move across SE TX on Tuesday and off the coast and temperatures will begin their fall from the 50’s into the 40’s. Cold air advection will continue into Wednesday and expect temperature to not warm much if at all from the 30’s on Wednesday under increasing clouds. WSW flow aloft from the downstream effect of a large upper level trough over the west coast will produce overrunning of warm and moist air on top of the dense and cold arctic surface pool. Short range models have a slightly better handle on the incoming air mass and will follow that guidance for Wednesday with highs mainly in the 30’s for most inland locations and the lower 40’s near the coast.

 

NYE Night:
Problems begin on Wednesday evening as lead short wave moves out of the SW US and across the arctic cold pool. Models have increased the chances for precipitation on Wednesday evening which is running about 12-18 hours faster than previous guidance was suggesting. Bigger concern is what will surface temperatures be at this time. Highs on Wednesday in the 35-38 range would only need to cool a few degrees to potentially lead to freezing drizzle or freezing rain. This seems at least possible NW of a line from Columbus to Brenham to Huntsville on Wednesday night where dewpoints in the upper 20’s would allow a few degrees of evaporational cooling to lower the surface temperature to near or below freezing. Main question is just how much precipitation actually develops and how well are the models handling the surface cold air as only a few degrees will make a big difference over portions of the area. For now will keep everything liquid SE of the above mentioned line which falls in close with WPC freezing rain probability guidance showing the highest threat along the I-35 corridor from San Antonio to Dallas. A lot of uncertainty in this part of the forecast and changes are likely over the next 48 hours.  

 

New Year’s Day:

Increasing overrunning pattern with widespread light to moderate rainfall developing over the region with cold surface arctic high entrenched at the surface. Temperatures will show almost no recovery likely in the mid 30’s most of the day. Some locations north and west could be very near freezing during the morning hours and even into the afternoon hours and will have to continue to watch for freezing rain mainly NW of a line from Columbus to Huntsville. Will see temperatures attempt to warm slightly by evening as warm air advection attempt to gain ground, but think the models are too quick in eroding the cold air.

 

Friday:

Powerful upper level system approaches the region from the west with significant lift and moisture advection into the region. Expect widespread rain and thunderstorms. Surface temperatures should start to warm into the 40’s during the day on Friday effectively ending any threat of freezing precipitation. Thinking is that the warm sector will not push inland keeping any severe threat offshore, but will need to watch for this potential in the coming days. Potential for heavy rainfall will increase and given the wet grounds in place from the 3-8 inches of rainfall over the last 2 weeks rises on area rivers and watersheds will be possible.

 

Storm system exits on Saturday, but clouds and rainfall will likely linger into Saturday afternoon along with cold temperatures. May finally see the sun again by next Sunday with a warming trend.

[bubba hotep]

It looks like a fair number of the 00z Euro EPS members keep the DFW area cold enough for some freezing rain/sleet/drizzle on the front end. It looks like transition zone will setup precariously close to DFW and a few degrees either way could make a difference. Precipitation will have to overcome the forecasted dry lower levels (FWD has been hammering this point in their discussions for days) and even if DFW starts out as freezing rain/ sleet temps look to eventually warm enough to melt everything before ice can cause any major issues. Overall, pretty disappointing as it initially looked like this air mass would be cold and deep enough to support snow across the DFW area.

[aggiegeog]

It looks like a fair number of the 00z Euro EPS members keep the DFW area cold enough for some freezing rain/sleet/drizzle on the front end. It looks like transition zone will setup precariously close to DFW and a few degrees either way could make a difference. Precipitation will have to overcome the forecasted dry lower levels (FWD has been hammering this point in their discussions for days) and even if DFW starts out as freezing rain/ sleet temps look to eventually warm enough to melt everything before ice can cause any major issues. Overall, pretty disappointing as it initially looked like this air mass would be cold and deep enough to support snow across the DFW area.

I would not count out temps being much colder than forecasted. Now moisture will be a concern early on along with how quickly temps moderate. 

[DFWWeather]

It looks like a fair number of the 00z Euro EPS members keep the DFW area cold enough for some freezing rain/sleet/drizzle on the front end. It looks like transition zone will setup precariously close to DFW and a few degrees either way could make a difference. Precipitation will have to overcome the forecasted dry lower levels (FWD has been hammering this point in their discussions for days) and even if DFW starts out as freezing rain/ sleet temps look to eventually warm enough to melt everything before ice can cause any major issues. Overall, pretty disappointing as it initially looked like this air mass would be cold and deep enough to support snow across the DFW area.

Given the dry layer aloft, more concerned with greater potential for evaporative cooling (should be substantial dewpoint depressions initially) effects and the likely precip mode being sleet over freezing rain. Freezing rain tends to be over done for our area with main precip phase usually ending up being sleet or just plain rain. The higher res models are a bit more aggressive with precip which makes sense given they are most likely colder.

[vwgrrc]

Well, it's quite surprised to see the forecasted temps for 1/1 keep dropping in the last few days, and it just dropped again to freezing.

[aggiegeog]

I am getting a bit concerned about a sweet spot developing around Canton or Tyler where temps could drop just cold enough (29-30) and the heavier moisture meet Thursday morning. This would require temps about 5 degrees cooler than what is shown by the models, but it is definitely within the error range of the models to be a few degrees warm when they expect the cold to be retreating faster than it usually does. 

[aggiegeog]

The RGEM continues to show a major ice storm from the Hill Country to Northeast Texas. The American models continue to be too warm with current temps especially in the Arctic air leading me to think that they may be too warm for the storm.

[cheese007]

Getting some wintry precip in Collin County

[Srain]

A quick look at observations across Central and E Texas into Western Louisiana show near or just below freezing temperatures at Georgetown near Austin. Temperatures in Lufkin are near 34-36 and in Jasper into the Piney Woods E Texas and Western Louisiana near Dequincy temperatures are near the 34-36F range. Dewpoints here in NW Harris County have dropped to 32 and the air temperature is 39F.

[bubba hotep]

A quick look at observations across Central and E Texas into Western Louisiana show near or just below freezing temperatures at Georgetown near Austin. Temperatures in Lufkin are near 34-36 and in Jasper into the Piney Woods E Texas and Western Louisiana near Dequincy temperatures are near the 34-36F range. Dewpoints here in NW Harris County have dropped to 32 and the air temperature is 39F.

 

FWD has slowly been expanding the WWA east this morning and I wouldn't be surprised to see that trend continue, esp. NE out towards Paris & Sulphur Springs.  For MBY up in Collin County, it looks like we could get into several hours of freezing rain early tomorrow morning but we should warm as the day goes on.  I guess I'll be up early to catch a fleeting glimpse of winter weather... 

[DFWWeather]

FWD has slowly been expanding the WWA east this morning and I wouldn't be surprised to see that trend continue, esp. NE out towards Paris & Sulphur Springs.  For MBY up in Collin County, it looks like we could get into several hours of freezing rain early tomorrow morning but we should warm as the day goes on.  I guess I'll be up early to catch a fleeting glimpse of winter weather... 

 

Wouldn't be surprised to see some of the western areas get upgraded to a Winter Storm Warning as time wears on. Very impressive temperature gradient across North Texas. Downslope component off Ozarks keeping northeastern areas much warmer than southwestern areas this morning. For example, 23°F at Comanche and 32°F at DFW. If the cold air spreads out more than progged the stage could be set for decent icing. It was a very interesting discussion from Cavanaugh last night about the formation of snow out west, when forecast soundings indicated freezing drizzle. Of course, if the freezing rain is heavy enough it could pull down warmer air from aloft. I'm still concerned with potential for more sleet, especially in areas already under a Warning, than freezing rain.

[bubba hotep]

Wouldn't be surprised to see some of the western areas get upgraded to a Winter Storm Warning as time wears on. Very impressive temperature gradient across North Texas. Downslope component off Ozarks keeping northeastern areas much warmer than southwestern areas this morning. For example, 23°F at Comanche and 32°F at DFW. If the cold air spreads out more than progged the stage could be set for decent icing. It was a very interesting discussion from Cavanaugh last night about the formation of snow out west, when forecast soundings indicated freezing drizzle. Of course, if the freezing rain is heavy enough it could pull down warmer air from aloft. I'm still concerned with potential for more sleet, especially in areas already under a Warning, than freezing rain.

Moisture return appears to be occurring much faster than anticipated, so maybe the wetter/ colder NAM will be closer to what happens tonight.

[aggiegeog]

Moisture return appears to be occurring much faster than anticipated, so maybe the wetter/ colder NAM will be closer to what happens tonight.

I think the NAM is close, if the precip is as heavy as the RGEM shows things will be very bad. Looks like temps will be above freezing south of I-30 in E TX, but I am keeping a very close eye on it.

[bubba hotep]

I'm not sure if we can post them and I am even less sure as to how accurate they are but the WxBell 12z 4k WRF/NAM has basically all of Collin and Denton county with 0.25 - 0.50 inches of freezing rain.  Given that temps look borderline at best, I would guess that accumulation is much lower but still might be enough to cause some issues on elevated surfaces. 

[vwgrrc]

NATIONAL WEATHER SERVICE FORT WORTH TX 946 AM CST WED DEC 31 2014

 

...UPDATED MODEL GUIDANCE CONTINUE TO COME IN COLDER THAN PREVIOUSLY EXPECTED...

[bubba hotep]

Updated graphic from FWD:

 

[vwgrrc]

It continues to downgrade the temps for the next 24 hrs 

Updated graphic from FWD:

 

[Srain]

Accidents reported in Mountain Home (Kerr County) on HWY 41 and I-10 due to freezing drizzle.

[bubba hotep]

We originally had a forecast high of 38 today, we got up to 34 and now are down to 33.  Not convinced that we won't surge back up later this afternoon but the CAA appears to be rather strong today.  

[Srain]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1217 PM CST WED DEC 31 2014

.UPDATE...
Temperatures are reluctant to warm at all today, currently ranging
from the mid teens north of I-20 to the mid 20s along the I-10
corridor. Max temps were lowered a good 4-5 degrees today.
Precipitation type was modified as well. Carrying occasional
freezing drizzle with a chance for sleet. Otherwise, changes were
minor. We're still looking for precip to increase in coverage and
intensity tonight with additional ice accumulations up to 1/4 inch
possible from the Concho Valley into the Big Country.

Johnson
 

[Srain]

Seagraves FD (Gaines County) reports Hwy 83 W of Seagraves totally iced over.

[DFWWeather]

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SAN ANGELO TX

1217 PM CST WED DEC 31 2014

.UPDATE...

Temperatures are reluctant to warm at all today, currently ranging

from the mid teens north of I-20 to the mid 20s along the I-10

corridor. Max temps were lowered a good 4-5 degrees today.

Precipitation type was modified as well. Carrying occasional

freezing drizzle with a chance for sleet. Otherwise, changes were

minor. We're still looking for precip to increase in coverage and

intensity tonight with additional ice accumulations up to 1/4 inch

possible from the Concho Valley into the Big Country.

Johnson

 

 

We need this deeper cold air to filter into DFW to make this a good ice storm. Need to get surface temps down to 28 or lower.

[ArmyGreens]

Currently sitting at 26 here in east El Paso. Forecast was 39 today. Concerned about precip type since nws office here is saying to warm for all frozen in the city.

[bubba hotep]

It is one thing to get trolled by the Euro snowfall maps at D10 but the day before is a different story     

 

However, the Euro EPS has always had a group of colder wetter members.  Everyone knows the different model bias but it is always tricky when you are in the transition zone and DFW has pretty much always been in that area for this event.  This is starting to remind me of how the Christmas day 2012 event unfolded.  The models and forecasters spent Christmas Eve scrambling around as they went from a cold rain to snow event.  However, the setup was totally different with that system, IIRC, and we had some nasty storms w/ hail overnight and then quickly transitioned to snow on Christmas day.

[Srain]

SJT is mentioning a significant storm across their WFO service area. Most of the guidance is off by a good 5- 10 degrees being entirely too warm.

[Quixotic1]

It is one thing to get trolled by the Euro snowfall maps at D10 but the day before is a different story

However, the Euro EPS has always had a group of colder wetter members. Everyone knows the different model bias but it is always tricky when you are in the transition zone and DFW has pretty much always been in that area for this event. This is starting to remind me of how the Christmas day 2012 event unfolded. The models and forecasters spent Christmas Eve scrambling around as they went from a cold rain to snow event. However, the setup was totally different with that system, IIRC, and we had some nasty storms w/ hail overnight and then quickly transitioned to snow on Christmas day.

Setup reminds me of Feb - Mar 1989. Cold rain storms became huge ice/sleet storms overnight. Wasnt forecasted at all. Hopefully we can keep the CAA and low DPs to help with the evaporative cooling once the system approaches.

[DFWWeather]

Setup reminds me of Feb - Mar 1989. Cold rain storms became huge ice/sleet storms overnight. Wasnt forecasted at all. Hopefully we can keep the CAA and low DPs to help with the evaporative cooling once the system approaches.

 

The Feb 1989 ice storm event associated with a 1060mb Arctic high (basically along the same path as this one) was very well forecasted by Harold Taft for DFW. National Weather Service did a pretty decent job 24 hours ahead of event. It was a little different as surface temps were in the upper teens and lower 20s when this event happened.

 

There was a surprise snow storm later in the month (it was on a Friday) that wasn't forecasted well at all. This left 5 to 6 inches of snow in west Fort Worth (9 inches in Weatherford).

[Srain]

Happy New Year gang. Be safe out there along and N of the I-35 Corridor if you are planning to travel late tonight into tomorrow.

[DFWWeather]

WITH REGARD TO THE KEY WEATHER FEATURES...THE STRONG UPPER TROUGH CURRENTLY DEVELOPING INTO WESTERN ARIZONA WILL EJECT INTO THE PLAINS WITH TWO DISTINCTIVE WAVES. THE FIRST WAVE OF ENERGY IS FORECAST TO MOVE ACROSS NORTHERN NEW MEXICO AND EASTERN COLORADO ON THURSDAY AND WILL BE RESPONSIBLE FOR THE WINTER WEATHER EVENT TONIGHT. PLENTIFUL PACIFIC MOISTURE...STRONG LOW LEVEL WARM AIR ADVECTION...AND SOME MID LEVEL FRONTOGENESIS WILL LEAD TO THE DEVELOPMENT OF WIDESPREAD PRECIPITATION FROM WEST TO EAST AFTER MIDNIGHT. SOME CONVECTIVE BANDS /SHOWERS/ ARE FORECAST TO DEVELOP IN THE AXIS OF FRONTOGENESIS TONIGHT WHICH IS FORECAST TO BE CENTERED FROM THE EASTLAND AND BRECKENRIDGE AREAS EASTWARD INTO THE DFW METROPLEX AFTER MIDNIGHT. WINTER WEATHER IMPACTS WILL BE ENHANCED LOCALLY NEAR ANY OF THE HEAVIER SLEET SHOWERS THAT DEVELOP IN AREAS WITH SURFACE TEMPERATURES NEAR OR BELOW FREEZING.

 

 

Interesting update from FWD in AFD.