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


Portastorm

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Yep, even if you went conservative with some blend of the GFS/Euro/Euro EPS (whatever it is at 00z)/NAM, you have to recognize the snow potential.   

Yep, especially since it would start in basically 24 hours or less.

 

Not to mention, Winter storm watches are already out to your west for FWD and well east along I-20 through Miss, and Alabama. Should be a good AM AFD read. I would suspect a watch with the morning package....of course it is SHV so I could easily be wrong here. :lmao:

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So when does the NAM cave? 00z GFS is south and Euro is kind of between the two but more GFSish. NAM was more north with this past system and the GFS had a number of runs keeping parts of Oklahoma dry that saw snow. What will FWD do with the overnight package?

So far FWD is sticking with the NAM saying there is a piece of energy the other models are not picking up on, which is factoring into the tilt of the trough to more neutral. They have a long but good read this morning and mentioned the 6z GFS was initializing towards the NAM.

Edit: When I've dealt with these setups in the past they always would always tell us to watch where the rain/snow line is, typically just north of that line is where the heaviest snow is as it has the most moisture.

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So far FWD is sticking with the NAM saying there is a piece of energy the other models are not picking up on, which is factoring into the tilt of the trough to more neutral. They have a long but good read this morning and mentioned the 6z GFS was initializing towards the NAM.

The GFS did come into alignment with the NAM. Neither show anything heavy in Texas, but both show 1-3 inches north of I-20. We will have to watch to see if the heavier stuff can shift south into our area.
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Morning briefing from Jeff:

 

Main upper level storm to cross TX tonight/Wednesday.

 

Freezing line at 700am this morning extended from Columbus to Waller to Conroe to Cleveland with Tomball and IAH at 33. Light freezing drizzle has been observed overnight/this morning at both College Station and Huntsville and both the wind sensors at Caldwell and Crockett are calm suggesting ice has accumulated on some elevated surfaces. TXDOT roadway temperatures are running 34-36 degrees on elevated bridges which has saved much of the area from any ice formation on those surfaces…appears the warm weather on Sunday helped with that aspect even for locations which have now been below freezing for many hours.  Light drizzle and mist should end this morning and temperatures will gradually rise above freezing across the entire area by 900-1000am. Saturated layer below 800mb will keep low level stratus clouds locked in place all day along with haze and fog.

 

Main upper trough approaches and moves across N TX tonight. Warm layer sampled in the CLL special sounding launch yesterday evening will begin to cool overnight especially in the College Station to Huntsville corridor as the cold pocket aloft moves over N TX. Forecast models are fairly impressive in their development of banded heavy snowfall over N TX tonight with just enough instability to likely generate a few lightning strikes. Could see periods of heavy snow is mesoscale bands over N and NE TX tonight/Wednesday morning with accumulations of 2-5 inches.

 

Over SE TX the sounding profile looks too warm to support sleet or snow and the surface temperature will be at or above freezing for all of the area overnight with no threat of freezing rain. While the profile does not support snow production from a high altitude, as was seen yesterday evening in Huntsville snow can be generated in the sub freezing layer just above the surface. Still think that any snow potential for tonight is very low across the region.

 

Lift will increase tonight and expect light ran and drizzle to develop across the region again and last into Wednesday. Rainfall amounts will once again be on the light side averaging less than .25 of an inch. Highs today will struggle to reach the 40’s and likely remain in the 40’s on Wednesday.

 

Slight warming onsets Thursday with highs breaking 50 before another strong cold front surges across the region Thursday night. Colder again on Friday with highs in the 40’s.

 

Next upper level storm system begins to dig into the SW US over the weekend with returning southerly winds overrunning the surface cold dome. Current model guidance has backed down on the rain chances over the weekend and generally warm surface temperatures toward 70 by Sunday as warm air advection becomes established.

 

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Cavanaugh is awesome.  I think he was the one who discussed the December '13 event as to why we were seeing reports of -SN rather than IP.  Something to do with supercooled droplets and learning how to freeze as the air T gets to -8C.  It's a sign of love that he takes the time to explain things.  Other AFDs seem incredibly dull by comparison.  

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Cavanaugh is awesome.  I think he was the one who discussed the December '13 event as to why we were seeing reports of -SN rather than IP.  Something to do with supercooled droplets and learning how to freeze as the air T gets to -8C.  It's a sign of love that he takes the time to explain things.  Other AFDs seem incredibly dull by comparison.  

 

He did one a couple of summers ago that was off the charts, it was for a low probability dry line event.  Most AFD would have simple been "dry and hot" blah blah.  He went way out in the deep water to describe how storms could fire and then mentioned that it was like a 5 - 10% event.  It ended up just being dry and hot 

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I don't know how this works but....the office last to jump on board, is the first to issue Winter Storm Warnings for the Tyler/Longview area.

 

 

URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE SHREVEPORT LA1000 AM CST TUE FEB 24 2015ARZ050-051-059>061-070>073-LAZ001>004-006-OKZ077-TXZ096-097-108>112-124>126-136>138-250000-/O.UPG.KSHV.WS.A.0003.150225T0600Z-150226T0000Z//O.NEW.KSHV.WS.W.0004.150225T0600Z-150226T0000Z/SEVIER-HOWARD-LITTLE RIVER-HEMPSTEAD-NEVADA-MILLER-LAFAYETTE-COLUMBIA-UNION AR-CADDO-BOSSIER-WEBSTER-CLAIBORNE-UNION LA-MCCURTAIN-RED RIVER-BOWIE-FRANKLIN-TITUS-CAMP-MORRIS-CASS-WOOD-UPSHUR-MARION-SMITH-GREGG-HARRISON-INCLUDING THE CITIES OF...DE QUEEN...NASHVILLE...ASHDOWN...HOPE...PRESCOTT...TEXARKANA...LEWISVILLE...MAGNOLIA...EL DORADO...SHREVEPORT...BOSSIER CITY...MINDEN...HOMER...FARMERVILLE...IDABEL...CLARKSVILLE...MT VERNON...MT PLEASANT...PITTSBURG...DAINGERFIELD...ATLANTA...QUITMAN...GILMER...JEFFERSON...TYLER...LONGVIEW...MARSHALL1000 AM CST TUE FEB 24 2015...WINTER STORM WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 6 PMCST WEDNESDAY...THE NATIONAL WEATHER SERVICE IN SHREVEPORT HAS ISSUED A WINTERSTORM WARNING FOR SNOW UP TO 4 INCHES...WHICH IS IN EFFECT FROMMIDNIGHT TONIGHT TO 6 PM CST WEDNESDAY. THE WINTER STORM WATCH ISNO LONGER IN EFFECT.* EVENT...AN UPPER LEVEL TROUGH WILL BE APPROACHING THE REGION  LATE TONIGHT BRINGING WITH IT A MIXTURE OF SLEET AND SNOW.  DURING THE DAY WEDNESDAY...THE UPPER TROUGH WILL BE DIRECTLY  OVERHEAD WITH MUCH OF THE PRECIPITATION CHANGING OVER FROM SLEET  TO SNOW. SLEET ACCUMULATIONS SHOULD BE LESS THAN ONE QUARTER OF  AN INCH WHILE SNOW ACCUMULATIONS AROUND 4 INCHES POSSIBLE.  PRECIPITATION WILL MOVE EAST OF THE REGION LATE WEDNESDAY  AFTERNOON.* TIMING...THE WINTER PRECIPITATION SHOULD BEGIN AFTER MIDNIGHT   TONIGHT AND CONTINUE THROUGH THE DAY WEDNESDAY. * IMPACT...IMPACTS WILL BE CONFINED TO MAINLY ELEVATED AND EXPOSED  SURFACES INCLUDING BRIDGES AND OVERPASSES. IF THE SNOW COMES  DOWN QUICKLY ENOUGH...THEN SURFACE STREETS WILL SEE  ACCUMULATIONS AS WELL.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHERCONDITIONS ARE EXPECTED OR OCCURRING. SIGNIFICANT AMOUNTS OF SNOWARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL IN ANEMERGENCY. IF YOU MUST TRAVEL...KEEP AN EXTRA FLASHLIGHT...FOOD...AND WATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY.
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Sounds like it. Hate that they are so reactionary. I am 10 miles from being in FWD's area and I so wish I was in it. Just this morning my forecast has gone from just rain to a Winter Storm Warning for 4 inches of snow.

 

 

000

FXUS64 KSHV 241637

AFDSHV

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SHREVEPORT LA

1037 AM CST TUE FEB 24 2015

.DISCUSSION...

BASED ON DATA FROM NEW NAM COMING IN WITH HIGHER SNOW

ACCUMULATION AMOUNTS TO AS MUCH AS 4 TO 5 INCH TOTALS ACROSS THE

INTERSTATE 30 CORRIDOR...WENT AHEAD AND UPGRADED WINTER WEATHER

WATCH TO A WINTER STORM WARNING. CONSIDERING NAM MODEL HANDLED

MONDAYS EVENT VERY WELL...WILL BE RELYING ON NAM FOR THIS UPCOMING

EVENT. HOWEVER...DID REMOVE OUACHITA AND LINCOLN PARISHES FROM

WATCH AND INCLUDED THEM IN THE ONGOING ADVISORY THAT EXISTS FOR

AREAS SOUTH OF INTERSTATE 20. NO OTHER SIGNIFICANT CHANGES TO

FORECAST AT THIS TIME. /05/

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Snow looks very likely for DFW metroplex and points ENE. For DFW temps will likely range from 32F in the Nern suburbs to 34-37F elsewhere. Time window for the higher snow rates will be around 3am - 12pm Wednesday. Looks like mostly wet snow, with accumulations ranging from 1 to 3", with isolated amounts around 4" -5" where snow bands develop.

 

This event is highly dependent on boundary layer temps. Temps colder or warmer than expected would change, rather significantly, the snow amounts. 

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Snow looks very likely for DFW metroplex and points ENE. For DFW temps will likely range from 32F in the Nern suburbs to 34-37F elsewhere. Time window for the higher snow rates will be around 3am - 12pm Wednesday. Looks like mostly wet snow, with accumulations ranging from 1 to 3", with isolated amounts around 4" -5" where snow bands develop.

 

This event is highly dependent on boundary layer temps. Temps colder or warmer than expected would change, rather significantly, the snow amounts. 

 

I'm up in the NE burbs and my NWS point for today is 35/27 and we are sitting at 29 right now.  Maybe we bust low with the cloud cover and sleet on the ground?  The results could be crazy for this with high bust potential.  If forcing sets up south it could just be heavy rain or very wet snow but the more north you go the better the rates will be.  Like you said, seeing 4"+ in the NE burbs isn't out of the question but probably just as likely for us to see nothing or just a dusting.

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I'm up in the NE burbs and my NWS point for today is 35/27 and we are sitting at 29 right now.  Maybe we bust low with the cloud cover and sleet on the ground?  The results could be crazy for this with high bust potential.  If forcing sets up south it could just be heavy rain or very wet snow but the more north you go the better the rates will be.  Like you said, seeing 4"+ in the NE burbs isn't out of the question but probably just as likely for us to see nothing or just a dusting.

You are sitting in a pretty good position, as most/all precipitation will probably stick from end to end. The fly in the ointment, like you said is about forcing setting up further south, with little precipitation over you.

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BTW, about my post 3.5 days ago about the disparity of the NAM and GFS for the lows today...GFS busted hard with it's forecasted 49F as low (48 hours away, it was still 49F)...we got down to 37F...it was funny looking at the GFS trend yesterday, with each run going colder by 1 to 2F every run. It also busted on precipitation, as a stronger CAA set up a nice CAD dome with drizzle. The GFS had no precipitation from 9am yesterday onwards...and we got drizzle most of the time until early this morning.

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