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fxus61 kpbz 210100 
afdpbz 


Area forecast discussion 
National Weather Service Pittsburgh PA 
900 PM EDT Sat Mar 20 2010 


Synopsis... 
a weak cold front will sag across counties immediately to the 
north of Pittsburgh tonight...but dry weather may be expected 
through Sunday. Low pressure approaching from the plains will 
generate rain from Sunday night into Monday night. 


&& 


Near term /through Sunday/... 
cold front continues to drop slowly from the eastern Great Lakes 
into the northern counties of the forecast area. All of the shower 
activity has remained well to the north of the front...primarily 
across lower Michigan and Ontario. The front is expected to decay as 
it enters the area...leaving a weak wind shift and minimal 
precipitation chances. 


Warm advection regime is expected to resume on Sunday as low 
pressure advances up the Ohio Valley...thus temperatures should 
once again make it into the middle to upper 60s. The model-timing of 
the low is such that rain should hold off until Sunday night...so 
only slight numbers were included along the stalled boundary. 


&& 


Short term /Sunday night through Tuesday/... 
low pressure is now expected to have only reached eastern Kentucky 
by Monday morning...which will delay the arrival of precipitation to 
the area. Will also diminish probability of precipitation Sunday night...but expect that 
most locations south and west of Pittsburgh should see precipitation 
by sunrise Monday morning. The low is then expected to drift north 
into eastern Ohio by Monday night and only reach central 
Pennsylvania by Tuesday morning. This will also result in keeping 
higher probability of precipitation into Tuesday. Still expect that precipitation amounts 
should be between half an inch and an inch through this portion of 
the forecast. With the upper ridge moving off the Atlantic coast and 
upper low then moving through the region...support for above normal 
temperatures will disappear...with temperatures expected to drop 
back to near normal numbers. Temperatures will be well above 
freezing Sunday night...and should be just warm enough (particularly 
north of I-80) Monday night that all precipitation should remain 
rain. 


&& 


Long term /Tuesday night through Saturday/... 
residual showers will diminish Tuesday night as the system exits 
to the east. Brief high pressure is prognosticated to cross the area 
Wednesday into Thursday for mainly dry conditions. Medium range 
models differ a bit handling low pressure projected to affect the 
area late week into next weekend. Will use low end chance probability of precipitation for 
now until better agreement/run to run continuity exists. Slightly 
above normal temperatures for midweek will cool to near normal 
by Friday/Saturday. 


&& 


Aviation /01z Sunday through Thursday/... 
VFR conditions may be expected through Sunday although middle level 
cloudiness will be abundant tonight. A generally light and 
variable surface wind is also forecast in response to a weak cold 
front that sagged to near a duj to phd line on Saturday evening. That 
boundary is expected to stall in vicinity of that line and hamper 
any prevailing wind direction. 


Low pressure approaching from the southwest will result in 
southeast, to easterly wind on Sunday...although speed should 
remain under 10 kts. On Sunday night, condition deterioration may 
be expected as moisture is advected over the upper Ohio region 
with the advance of the low. MVFR conditions will persist 
Monday/Tuesday as the system slowly crosses the region...and periods 
of IFR are possible Monday in heavier showers. High pressure will 
rebuild over the region Wednesday/Thursday and provide for mainly 
VFR conditions. 


&& 


Pbz watches/warnings/advisories... 
Maryland...none. 
Ohio...none. 
PA...none. 
WV...none. 


&& 


$$ 


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