362 
fxus61 krlx 202020 
afdrlx 


Area forecast discussion 
National Weather Service Charleston WV 
415 PM EDT Sat Mar 20 2010 


Synopsis... 
high pressure remains in control through tonight. Low pressure 
system passes Monday...with showers lingering through Tuesday. Next 
bigger system expected by late in the week. 


&& 


Near term /through Sunday/... 
high pressure dominates tonight with light winds and enough 
cloudless skies to go below model temperature guidance. 


Models in very good agreement on another large upper low approaching 
from the Southern Plains. Models have slowed the system a 
little...and the warm front approaching...associated with the first 
short wave rotating around the upper low...will not affect the area 
with showers until Sunday afternoon...and then mostly in the south. As 
is usual with these type systems...low level flow increases from the 
southeast Sunday...which cools east facing slopes of the mountains 
while increasing temperatures west of the mountains...and produces a 
bit of a rain shadow west of the mountains. Thus...maximum temperatures and 
probability of precipitation show this. Any showers will be light...though...as the system 
will be just starting to affect US. No thunder forecast Sunday as 
model instability and moisture not yet sufficient. 


&& 


Short term /Sunday night through Tuesday/... 
850 mb moisture convergence increases over southern and mountain 
counties around 00z Monday then lifts northwest into southeast Ohio before 12z 
Monday. Have 2 rain maximums Sunday night into Monday morning along 
the southeast upslope and another in southeast Ohio. 850 mb winds increase to 
around 50 knots late Sunday night. Have gusts at or above 30 knots over our 
High Mountain locations 06z to 12z Monday..before weakening. 


Have higher probability of precipitation lifting north late Sunday night...with probability of precipitation briefly 
lowering before 12z Monday across our southern counties. Timing 
wind shift to southwest...associated with the low lifting from SW to 
NE...beginning after 12z in SW Virginia and reaching northern counties toward 
21z. Will have a pop maximum along that wind shift. Do think there 
will be enough instability from cooling aloft and the boundary to 
include chance thunderstorm for Monday. Have temperatures peaking 
ahead of that wind shift...then falling across southern counties 
during Monday afternoon. That cooling delayed until late in the day 
or Monday evening in the north. 


Plenty of moisture lingers Monday night into Tuesday...around the 
upper low. Will hold probability of precipitation higher longer. Also...thought 12z NAM 
was a bit too cold on 850 mb temperatures...but 00z ecwmf too warm. 
Still want to mention a rain and snow shower mixture developing over 
our high terrain from SW Virginia into WV overnight Monday night into 
Tuesday morning. 


No big changes in our quantitative precipitation forecast...still have widespread .5 to 1. Into from 
Sunday night into Monday night. Will include southeast Ohio in the hazard 
for stream flood concerns...but no reason to Post any watches at 
this time. 


&& 


Long term /Tuesday night through Saturday/... 
East Coast low pressure heads out to sea Tuesday night...with 
lingering moist upslope in mountains...yet waning. Still enough to 
include chance probability of precipitation in the WV mountains initially Tuesday evening. 


Wednesday through Thursday...we will be in a brisk zonal flow. So 
temperatures look to not deviate very much from normal /only 
slightly above/. For a few days now...it looked like the midweek 
period would be dry...but the models are beginning to have issues 
with possible small embedded waves within the flow. One such wave 
comes through Wednesday afternoon or evening...with at least clouds 
as per European model (ecmwf) and perhaps even light showers as per GFS. This is a 
departure from previous runs...and for now will only include slight 
chance probability of precipitation with the feature because of weakness of wave and 
inaccessibility to moisture. 


A better southern stream wave...with more moisture availability from 
south-southwest low level flow ahead of it...is still expected 
sometime in the Thursday night to Friday night timeframe. HPC-based 
probability of precipitation accepted with this system...with 50-ish probability of precipitation for the southeast 
half of the area and still at least a chance for the remainder of 
County Warning Area. These probability of precipitation will probably go higher as timing...and nature of 
the system...become better understood in coming days. Model spread 
becomes especially problematic as to what happens on the back side 
of that system by Saturday. 


&& 


Aviation /20z Saturday through Thursday/... 
18z Saturday to 18z Sunday... 
high pressure in control through tonight...warm front approaches 
from the southwest Sunday. VFR mainly scattered clouds tonight. 
After 12z Sunday...increase in clouds with ceilings lowering to 
around 5000 feet in scattered showers by 18z well south of a 
heights-crw-bkw line. 


After 18z Sunday... 
IFR possible in showers/isolated thunderstorms Sunday night and 
Monday. 


&& 


Rlx watches/warnings/advisories... 
WV...none. 
Ohio...none. 
Kentucky...none. 
Virginia...none. 


&& 


$$ 
Synopsis...ktb/mdp/jmv 
near term...jmv 
short term...ktb 
long term...mdp 
aviation...