Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 280548
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
148 AM EDT Tue Mar 28 2017

.SYNOPSIS...
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.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Isolated showers breaking out early this morning across the
Central and West Central Mountains...with scattered coverage
increasing over the Laurel Highlands. This in response to
approaching midwestern upper trough pushing through the lower
Ohio Valley...inducing northward increase of deep layer moisture
into central PA from WV and VA. PW increasing to over 1.0" up to
the I-80 corridor at this hour...as sfc low tracks into south
central OH...and moisture pools along and north of inverted sfc
extending from the WV pandhandle ESE to Chesapeake Bay.

Shower arrival is right on time with previous forecasts, and
while showers look to be mostly hit or miss...POPs will increase
to around 50pct. Developing frontogenetical forcing across the
northwest mountains is likely to result in a better chance of
steady rain up there toward dawn.

Increasing easterly low level flow ahead of aforementioned
sfc low pressure will promote nearly homogeneous min temps
within a few degrees of 50F across the entire area.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
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.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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.

Outlook...

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

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

Thu...VFR/No sig wx.

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

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...La Corte
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Lambert/Gartner
AVIATION...Jung/La Corte



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