532 
fxus64 ksjt 191210 
afdsjt 


Area forecast discussion 
National Weather Service San Angelo Texas 
710 am CDT Friday Mar 19 2010 


Discussion... 
see 12z aviation discussion below. 


&& 


Aviation... 
a strong cold front will move south across the terminals this 
evening and overnight as a potent upper level storm system 
approaches from the west. VFR conditions prevailing early this 
morning but will likely see MVFR stratus develop throughout the 
morning hours before scattering out after 18z. South winds will 
increase ahead of the front today with winds gusting to 25 knots 
through afternoon. North winds will increase and become gusty 
behind the front as it progresses south overnight. Showers and 
thunderstorms are expected to develop along and ahead of the 
front overnight with MVFR/IFR ceilings developing behind the front 
early Saturday morning. Gusty north winds continue on Saturday 
along with lingering stratus. 


&& 


Previous discussion... /issued 421 am CDT Friday Mar 19 2010/ 


Short term... 
main challenge in the short term will be precipitation chances this 
evening and overnight as a strong cold front surges southeast across 
the area. Upper trough will deepen over the southern rockies today 
then close off and move east across the Red River valley Saturday 
and Saturday night. Models in good agreement with timing of the 
associated cold front as it moves southeast across the area during 
the overnight period. Low level moisture will continue to increase 
ahead of the front today along with increasing south winds. Low 
level stratus will spread north across much of the area this morning 
as low level jet continues to strengthen through middle morning. 
Partly cloudy skies expected by afternoon with stratus scattering 
out as boundary layer warms and mixing increases. Surface cold 
front will be entering the Big Country around 03z then continue 
south overnight and exit the far southeast counties shortly after 
12z Saturday. Forcing along the front along with increasing lift 
with the approaching upper trough will result in showers and 
thunderstorms developing over much of the area tonight. Will 
maintain highest probability of precipitation over the Big Country and eastern zones 
where best moisture will reside. 


Forecast becomes quite tricky towards daybreak over northern zones 
as strong cold air advection develops in wake of the front. Latest 
NAM shows both 850 and 700 mb temperatures lowering to around minus 04c 
over western portions of the Big Country with surface temperatures dropping 
into the middle 30s. Could see some snow mix in with the rain at times 
just before daybreak but expect the best chance of this occurring 
after 12z. 


24 


Long term... 
a chance of wraparound precipitation Saturday...as strong upper 
low intensifies along the Red River...and moves east. Snow may mix 
in with the rain in the Big Country including Abilene...as GFS/NAM 
forecast soundings are below freezing. Snow amounts should be 
light...and with temperatures in the middle 30s...snow should melt as it 
falls. Lower portion of forecast soundings near surface is dry 
adiabatic...which is not realistic given cloud cover...thus expect 
colder temperatures than GFS MOS guidance. Highest daytime 
temperatures Saturday will actually be in the early morning in 
many areas. Wind chills will be in the lower 20s in the Big 
Country Saturday morning. 


Light freeze likely in most areas Sunday morning. With winds 
staying up however...do not think they will slip into the upper 
20s except in protected areas. Coldest temperatures may be Monday 
morning...at least south of the Big Country... where winds will be 
lighter and good radiational cooling conditions prevail. 


Otherwise...another upper trough/cold front may impact the region 
the middle of next week. Have a slight chance if thunderstorms... 
Wednesday into Thursday. 


&& 


Preliminary point temps/pops... 
Abilene 71 34 36 31 56 / 20 70 40 0 0 
San Angelo 75 38 44 31 62 / 10 50 30 0 0 
Junction 75 44 50 32 62 / 10 50 30 0 0 


&& 


Sjt watches/warnings/advisories... 
none. 
&& 


$$ 


99/99/24