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Area forecast discussion 
National Weather Service Shreveport la 
1008 PM CDT Friday Mar 19 2010 


Discussion... 
busy evening this evening...as the short term forecasts have come into 
good agreement with the 12z European model (ecmwf) run...painting more of a doom 
and gloom winter weather scenario for the northwest sections of the 
forecast area Saturday night and Sunday. These forecasts are much 
farther S with the closed low as it deepens rapidly/significantly 
Saturday evening over southern OK/North Texas...before gradually translating 
it eastward between txk and shv by 12z Sunday. Not much change in the 
last 24 hours with the overall timing of the front/its associated 
convection...with these storms reaching the western sections of East 
Texas/southeast OK shortly after daybreak Saturday. In fact...convection has 
blossumed in the last few hours along the front/dry line intersection 
across central OK/west-central Texas...and should continue to build S and 
March east overnight as it encounters a better low level moisture 
fetch across central Texas. Instability still looks to remain meager 
at best across much of the region Saturday with the arrival of the 
frontal passage...but can/T rule out an isolated severe storm or two given the 
extent of the forcing...and low wet bulb zero heights. Still 
looking for around an inch-inch and a half at most of quantitative precipitation forecast with 
this system for the weekend. 


Concerning the winter weather threat...forecast soundings and 
partial thicknesses all suggest the rain changing over to mostly 
snow late Saturday evening over SW Arkansas/southeast OK/NE Texas as the system 
begins to wrap up...with snowfall coverage/intensity increasing 
Sunday morning across these areas on the north and west side of the low. 
Have issued a Winter Storm Watch for late Saturday night/Sunday for 
Red River and Bowie counties in East Texas...McCurtain Colorado OK...as well as 
our 3 northwest counties in SW Arkansas...with the expectations of seeing possibly 
2-5" of snow...with amounts possibly nearing 7" over northern McCurtain 
County. Very steep lapse rates near the core of the closed low 
(~7.5-8 c/km) suggests the possibility for thundersnow across southeast 
OK/extreme NE Texas...which would enhance snowfall rates despite 
temperatures near/slightly above freezing for the duration of the event. 
Was not confident enough to extend the watch farther east into SW 
Arkansas...or farther S into NE Texas near the I-20 corridor...as temperatures 
should remain slightly above freezing...and the best forcing 
remains farther north and west. Will allow the middle shift to make the call 
in a possible upgrade to a Winter Storm Warning across 
all/portions of the watch area...with winter weather advisories 
also possible for areas surrounding the watch. 


Have also lowered temperatures Sunday as well in the watch area...as strong 
cold advection/precip/tight pressure gradient will not allow for 
much of a rise in temperatures. It should be noted that lake wind/wind 
advisories will also be needed this weekend...as wind gusts of 
35-40 miles per hour is expected. This may cause for some blowing of snow 
across extreme NE Texas/southeast OK/possibly SW Arkansas...creating dangerous 
travel conditions. 


As for tonight/S probability of precipitation...did lower probability of precipitation a tad for our far western 
sections of the forecast area...while also making a few minor 
adjustments to temperatures. Will be updating the severe weather potential statement shortly for the 
expected winter weather threats. 


New prelims follow below. Zone update already out...grids will be 
available shortly. 


15 


&& 


Aviation... 
a deepening upper level disturbance is prognosticated to move from The Four 
Corners area...southeast to over the four state area from Saturday 
through Sunday. The movement of this feature should push a cold 
front toward the I-30 corridor around 20/20z...and through all the 
taf sites by 20/06z. Widespread rain showers/thunderstorms and rain expected to occur in the 
vicinity of the frontal zone Saturday afternoon and Saturday night. 
Precipitation may change to snow late Saturday night in the txk area. 


Ceilings should gradually lower on Saturday to MVFR levels by 20/12z 
over the west sites...tyr...lfk...ggg...and by 20/22z over the rest 
of the taf sites. Visibilities at times will be IFR/MVFR in rain on Saturday 
and Saturday evening. Winds are expected to be from the south and 
southeast at 10-15 knots Saturday shifting to the northwest at 15-20 
knots after frontal passage. /03/ 


&& 


Preliminary point temps/pops... 
shv 50 65 34 40 33 / 10 80 70 50 20 
mlu 47 71 38 44 36 / 0 70 80 60 40 
deq 50 55 33 35 33 / 30 90 80 60 40 
txk 50 58 34 38 34 / 20 80 80 60 40 
eld 46 65 36 42 34 / 0 70 80 60 40 
tyr 53 55 33 44 34 / 30 90 20 30 10 
ggg 50 59 32 44 32 / 20 90 50 40 20 
lfk 53 63 34 49 33 / 10 80 40 30 10 


&& 


Shv watches/warnings/advisories... 
Arkansas...Winter Storm Watch from late Saturday night through Sunday 
afternoon for the following zones: arz050-051-059. 


La...none. 
OK...Winter Storm Watch from late Saturday night through Sunday 
afternoon for the following zones: okz077. 


Texas...Winter Storm Watch from late Saturday night through Sunday 
afternoon for the following zones: txz096-097. 


&& 


$$ 


15/03