316 
fxus61 kctp 191852 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
252 PM EDT Friday Mar 19 2010 


Synopsis... 
unseasonably mild and tranquil weather will continue through much 
of the upcoming weekend. Unsettled weather conditions are 
anticipated from late Sunday through early next week as a slow 
moving low pressure system lifts from the Southern Plains toward 
the middle Atlantic region. Another area of high pressure will bring 
another string of dry weather for the middle to latter part of 
next week with temperatures slightly above normal. 


&& 


Near term /until 6 am Saturday morning/... 
looking for a close copy of last nights conds overnight 
tonight. Save for a few high clouds moving across from time to 
time skies will again be clear. Increasing dewpoints ahead of 
slowly approaching weather system will keep min temperatures up few 
degrees especially over the lower susq. 


&& 


Short term /6 am Saturday morning through 6 PM Saturday/... 
in a continuing trend...the models have been slowing the appch of 
the next system...as the trough digs and eventually cuts off over 
the MS valley. This will serve to help The Heights rise over the 
eastern states and continue our long string of really nice and really 
dry weather. Weak front tries to nudge in from the northwest on Sat...and could 
help to keep things cooler than curr forecast in the northwest. But...with 
trend the way it has been and MOS guidance running too cool...will 
keep them up for now. Expect maxes in the 60s and l70s Sat and 
u50s and 60s on sun. Ridge axis does move to our east by sun...but 
slowing of the central U.S. System will keep moist isen lift to 
our north for the most part. 


&& 


Long term /Saturday night through Thursday/... 
guidance appears to be slowing with arrival of moisture from next 
weather system. At this time it appears low level/mid-lvl moisture arrives sun as 
a weak boundary slides southeast stretching from southeast Ontario to the 
southern Ohio River valley. This should increase clouds across the northwest 
mountains sun...then gradually increase as the boundary sags further southeast 
across the County warning forecast area. At this time have adjusted back the probability of precipitation for sun only a slt 
chance across northwest prior to 18z...then gradually increase late afternoon/evening 
into Monday. Surface ridge off the Carolina coast and middle-level ridging has 
remained strong thus slowing the eastward propagation of the 
developing shortwave and 500mb vorticity maximum. 


850mb temperatures warm under a decent southerly flow...advecting temperatures or 
6-9 degree c into the lower susq-valley Sun afternoon. The limiting factor 
for warm temperatures is increasing clouds from northwest to southeast thus have sun maximum 
temperatures of m50s northwest mountains...low to middle 60s elsewhere. Optimal conds 
would result in 3-5 degree f warmer...especially across the lower susq-valley. 
Gefs members are pointing towards an atmos river developing from the 
Carolinas to Maryland...early Monday as shortwave pushes into the tenn 
valley. Guidance also points towards precipitable water values or nearly 
1... compared to prior solutions this has marginally 
backed off thus introducing a slightly lower confidence. 


Ensemble data is in high agreement with bulk of moisture arriving 
Monday. Quantitative precipitation forecast totals between 0.30-0.60 along and east of the Laurel 
Highlands. Middle-level instability is marginal for Monday...however went 
ahead and noted the slt chance for thunder. It appears this will be 
focused along and east of the Laurel Highlands through susq-valley. 
Overnight temperatures Sun night and Monday night across a portion of the northwest mountains 
may be cool enough to allow rain to mix at times with snow...no accums 
are anticipated at this time. 


Tuesday will feature improving weather from west to east as the shortwave departs 
the region...lingering moisture across eastern portion of County warning forecast area. 
Confidence is increasing that trough axis will quickly depart as 
well with a return to seasonal conds Wednesday/Thursday of next week...then 
possibly another system approaching from the west late next week. 
Temperatures should be warm enough to limit any precipitation as rain. 


&& 


Aviation /19z Friday through Wednesday/... 
widespread VFR expected to continue into the evening as fair 
conditions prevail. Later in the period...a low pressure system passing 
north of PA will drag some low level moisture into northwest PA by early 
Saturday morning. Reflected this in tafs by dropping ceilings at kjst 
and kbfd to mvrf threshold...while keeping all other airfields 
VFR through the entire period. 


Outlook... 
Sat-sun...no sig weather expected. 
Monday...rain/IFR ceilings possible. 
Tuesday...shra/IFR ceilings possible. 
Wednesday...mainly VFR. 


&& 


Fire weather... 
a string of sunny and warm days has lead to very dry conditions across 
central PA...with relative humidity values below 30 percent the 
last several afternoons and quick drying of fine fuels. Winds 
however have been light due to an area of weak high pressure 
dominating the weather over the region. Latest observation are indicating 
small to moderate increase of dewpoints and rhs compared to this 
time yesterday at most RAWS stations across PA...at a time of day 
when rhs and...to a lesser extent dewpoints...should be 
decreasing. This is likely in response to a moist flow of air 
beginning ahead of approaching weather system. 


Have been monitoring the potential for increasing winds over the 
weekend ahead of the approaching weather system and possible red 
flag conditions. However...at this time the movement east of the 
system has slowed. This should keep winds below red flag criteria 
and low level moisture will continue to increase. 


The next chance of rainfall will be Sunday night or Monday from 
the slow moving weather system...which will linger into the first 
part of the new week. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...Lambert/steinbugl 
near term...gartner 
short term...gartner 
long term...beachler 
aviation...gartner/Dickey 
fire weather...gartner 

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