Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 270213
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1013 PM EDT Sun Mar 26 2017

.SYNOPSIS...
A cool-moist easterly flow will keep it damp over most of the
forecast area tonight. A frontal system will move back into the
region overnight and remain nearly stationary before a cold
front finally ushers in cooler and drier air during the day
Tuesday.

The drier conditions will continue for mid week before a new
storm system approaches for the end of the week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
The region remains firmly ensconced in a low level cold air
damming pattern this evening with stratus covering the entire
CWA. Regional radar loop at 02Z showing a band of showers
moving into the Alleghenies associated with approaching
shortwave. As attendant southerly low level jet overruns dome of
cool air across central Pa, expect rain to overspread the
rest of the region between 02Z-05Z. Blend of near term models
support POPS near 100 pct with rainfall overnight of between a
quarter and half inch over much of central Pa, with the lower
amounts across the Lower Susq Valley and northwest mountains.
Although the entire region will remain in stable air east of
stationary front, models indicating enough elevated instability
ahead of shortwave to perhaps support a few rumbles of thunder
overnight, mainly across the western counties.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Early showers should shift east of the region, as shortwave and
associated low lvl jet exit the area shortly after 12Z Monday.
Low level stability indices indicate that the surface warm front
will lift northeast across the CWA by midday, as it`s
associated sfc low moves down the St. Lawrence River Valley.

Model soundings support lingering low clouds across the
northwest mountains, where southwest flow rises over the higher
terrain. Elsewhere, expect brightening skies by midday, with the
most sunshine expected over the southern valleys. The partial
sunshine, combined with ensemble mean 850mb temps of around 7C,
should support max temps in the low 70s across the southern
valleys. More cloud cover expected across the northern half of
the state, where maxes should be mostly in the 60s.

&&

.LONG TERM /MONDAY 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 overnight tonight into early Monday. It
has a good surge of moisture and one or more distinct ribbons
of llvl theta-e convergence that should result in some nearly
north-south oriented bands of briefly heavier showers. Thus
nearly all operational and blended/ensemble guidance shows a
very high probability of rain overnight tonight into Monday.
Most of the guidance shows the peak chance of rain from
0000-1200 UTC Monday. Then things improve during the day Monday.

The second wave moving northeast and right up the Ohio River
Valley comes in overnight Monday into Tuesday. 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.

The second event 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 good day as high pressure builds in from the
northwest. The dry air and high pressure are in all the 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 /02Z MONDAY THROUGH FRIDAY/...
Made a few more changes here at 7 PM. Second band of showers
now in western PA. Band over OH not so widespread in nature.

Earlier discussion below.

First band of showers falling apart, as it moves into central
PA. Several more bands of showers over OH.

Made some changes to 21Z TAF package, some of which will be
used in the 00Z TAF package. Expect some improvement later
Monday, as winds shift more to the southwest.

A moist east/southeast low level flow will support widespread
low MVFR to LIFR conditions into Monday. Aside from pockets of
drizzle/mist/fog, the main period of rain should be tonight
between about 27/00z to 27/12z, tapering off from west to east
Monday morning.

Conditions will improve slowly later Monday morning with central
and eastern terminals likely rising to VFR by early to mid
afternoon. A stray afternoon thunderstorm cannot be ruled out,
especially over the south.

Outlook...

Tue...Sub-VFR with periods of rain.

Wed...MVFR becoming VFR early.

Thu...VFR early, Increasing chance of rain and lowering
conditions late in the day into Thursday night.

Fri...Breezy with showers. MVFR to IFR conditions possible.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Grumm/Lambert/Gartner
AVIATION...Martin



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