Area Forecast Discussion
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FXUS61 KCTP 271558
Area Forecast Discussion
National Weather Service State College PA
1158 AM EDT Mon Mar 27 2017
An area of low pressure will be moving northeast across the
Upper Great Lakes region this morning, pushing a warm front
northward across the District.
Unseasonably mild conditions are expected this afternoon
Cooler and dry weather will follow for Wednesday and Thursday.
A new storm system will approach for the end of this week with
the potential for more inclement weather.
.NEAR TERM /TODAY/...
Drier air can be seen invading from the west. So far much of it
is overshooting the low clouds/moisture trapped in the cool air
damming regime over central PA, but the mixing down is starting
to become evident over the SW where JST and AOO have both
skycover improve rapidly.
LAV and MET MOS guidance shows more of a mix of sun and clouds
developing today. The model guidance also indicates a quick
rebound/warmup in temps back into the 60s to near 70 deg F in
the south this afternoon.
RAP guidance shows us developing a modest amount of instability
over about the southern 1/3 of the CWA this afternoon, and the
meso-anal shows this already beginning over SWRN PA where the
sun is breaking through the clouds. I kept small chance pops
over the south to cover the potential for an isolated shower or
It will tend to become cloudy with a renewed chance of showers once
again tonight as the next wave of low pressure moves into Ohio.
Lows will be very mild in the 40s to lower 50s.
.SHORT TERM /TUESDAY/...
The storm will pass just south of PA Tuesday with periods of
light rain that will tend to taper off during the afternoon. It
will be another mild day in the 60s in most locations.
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
This period starts out with above normal heights over the
eastern U.S. Several lows weaken as they move into this blocked
flow and are forced to move to our west.
The first wave is comes through early today. It has a good
surge of deep layer moisture preceding it, and one or more
distinct ribbons of llvl theta-e convergence that have resulted
in some quasi north-south oriented bands of briefly heavier
showers. Most of the guidance shows the peak chance of rain
ending from SW to NE across the region between 0900-1400 UTC
today. improving conditions will follow for the midday and
afternoon hours today.
The second wave moving northeast and right up the Ohio River
Valley comes in overnight tonight across the western part of the
state, and Monday into Tuesday over the eastern half or so of
Another similar surge of +2-3 sigma Pwat air precedes the
passage of this area of low pressure and will once again result
in a high probability for showers, but generally light to
locally moderate 12 hour rainfall amounts.
This second ares of low pressure will push the warm moist air
off to our south Tuesday night into Wednesday. Chance of rain
should drop overnight Tuesday 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
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.
.AVIATION /16Z MONDAY THROUGH FRIDAY/...
MVFR/IFR conditions are already beginning to improve over SWRN
PA. Expect the improving trend into the afternoon with MVFR to
VFR conditions likely by mid to late afternoon.
VFR early will deteriorate once again overnight as a new storm
system spreads showers our way.
Tue...VFR/MVFR with periods of rain.
Wed...MVFR NW 1/3 becoming VFR.
Thu...VFR/No sig wx.
Thurs night-Fri...Sub-VFR restrictions/rain likely.
NEAR TERM...La Corte/Lambert