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FXUS61 KCTP 280218

Area Forecast Discussion
National Weather Service State College PA
1018 PM EDT Mon Mar 27 2017

An area of low pressure will move along or just south of the
Mason-Dixon line late tonight and Tuesday. High pressure will 
build down out of southern Canada and bring cooler and drier 
weather for Wednesday and Thursday.

A new storm system will approach for the end of this week with
the potential for more inclement weather.


Partly cloudy and dry conditions this evening, as central Pa
remains located in region of upper level ridging between
shortwave exiting New Eng and upper low approaching from the

Clouds will return with a renewed chance of showers once again 
tonight, as upper low and associated surface wave approach from
the west. Near term model guidance indicates arrival time of 
showers will be between 02Z-05Z across the southern counties 
and late tonight in the north. In general, showers look to be 
hit or miss, with POPs around 50pct. However, developing fgen 
forcing across the northwest mountains is likely to result in a 
better chance of steady rain up there toward dawn. 

02Z surface analysis shows a warm front lying across south
central Pa. However, this boundary is progged to retreat south 
of the border overnight, as easterly low level flow develops 
ahead of approaching low pressure. A blend of latest guidance 
supports min temps within a few degrees of 50F across the entire


Weak surface low will track just south of the Mason Dixon Line 
Tuesday. However, bulk of the latest near term model guidance 
indicates the best chance of rain will be across the northern 
mountains, where models place a developing band of fgen 
forcing. A cool, rainy day appears likely in this part of the 
state, while thin spots in the overcast and only scattered 
showers allow temps to rise into the 60s over much of central 
Pa. Along the southern tier, readings could reach the low 70s if
warm front manages to lift north of the Mason Dixon. 

The guidance continues to show the development of some 
instability over southern areas by afternoon, where a 
thunderstorm cannot be ruled out, especially in the vicinity of
warm front along the MD border. 

Showers should wind down from west to east Tuesday evening, as
weak surface low passes off the Mid Atlantic coast.


The long term period will start with a frontal system and 
associated precipitation exiting the region and heights building
aloft. Building high pressure will push the warm moist air off 
to our south Tuesday night into Wednesday. Wednesday should be 
a relatively nice day (though with some mdt northerly wind gusts
at times, as high pressure builds in from the northwest. The 
dry air and high pressure are in all of the most recent 
guidance, implying Wednesday and Thursday should be relatively 
nice days.

High pressure, dry air, and normal to slightly below normal 850
hPa and 925 hPa temperatures imply near normal daytime highs.

Most of the 26/00-06Z U.S. and int'l model guidance (and EFS)
indicates more of southern...shearing storm track for late in
the week...thanks to a stronger and more wwd position of a deep
nrn stream vortex across the Canadian Maritimes. 

The trend of the big model discrepancy for late this week and 
this weekend (between the GFS and EC over the past several days)
has trended toward the GFS and its ENS members with southern 
stream energy and its moisture being prevented from amplifying 
with an associated storm track to our west. 

Rather, what we see is a shift of the primary southern stream 
sfc low track to our south as the potent midweek southern stream
sfc/upper low (that will be trying to take the turn northeast 
across the Mid Miss Valley twd the Great Lakes) encounters great
resistance from the notably stronger WNW upper jet core 
defining the northern stream that will be situated from the 
Upper Glakes to the Mid Atl Coast. 

With this type of consensus storm track, pops will be somewhat 
less for Friday and Saturday (compared to a heavily weighted 
EC/ECENS solution) and limited to mainly the southern half of PA
where some rain (or even an elevation-dependent rain/wet snow 
mix) with expansive cooler and drier air north of PA.


VFR conditions this evening will deteriorate with lowering 
ceilings and dropping visibilities as lower atmosphere moistens 
rather rapidly tonight on light southeast flow. Approaching 
system will bring showers into most areas overnight, with damp 
rain/shower activity lasting through Tuesday. This will bring 
significant restrictions to flying conditions, with widespread 
MVFR to IFR expected.

Cooler, drier air filters in behind the system late Tuesday 
night into Wednesday with a slow improvement in conditions.

VFR conditions Thursday, before a large rain-making system 
affects the area Thursday Night through Saturday.


Tue...IFR/MVFR across the region in showers/light rain.

Wed...Morning restrictions, gradually improving to VFR most

Thu...VFR/No sig wx. 

Thurs Night-Sat...Sub-VFR restrictions/rain likely.





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