Area Forecast Discussion
Issued by NWS State College, PA

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197
FXUS61 KCTP 301342
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
942 AM EDT Sun Apr 30 2017

.SYNOPSIS...

A nearly stationary front will remain just south of PA today. A
strong Cold front will move across the region on Monday
followed by brisk west to northwest winds and cooler air for
Tuesday. Fair weather with milder temperatures will occur
Wednesday under a weak ridge of high pressure. Deep moisture
will flow north into the state Thursday afternoon through Friday
bringing a return to inclement weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

Meso anal shows the stalled surface front extended from
southern Ohio to northern Virginia into the northern Chesapeake
area early this morning. The frontal system aloft shows up
nicely in the LI fields and is further north from near CLE east
to just south of ERI then sharply SE down into the Laurel
Highlands. This shows up spectacularly on the high resolution
GOES R data with the convective clouds riding up over this
elevated boundary while the cool air damming can be seen with
the stable low clouds hanging tough east of the Alleghenies
plateau.

For today, shallow cool air damming will persist across much of
the Central and Eastern, Ridge-Valley region of the state where
a blend of the very cool NAM was used with the warmer NBM and
previous fcst temps. Highs this afternoon will vary from the
L60s across the higher terrain north and east of IPT and SEG,
to the mid and upper 70s in the valleys near and to the west of
state route 219 in western PA.

Followed closely with a combination of the 07Z RAP and HRRR to
time an expected area of showers that should blossom around
17-18Z across the western mountains and S-Central PA (over the
western/southern extent of the sfc-925 mb front), then move
northeast across the Central Mountains during the mid to late
afternoon timeframe, before weakening toward dusk.

QPF is expected to be generally a few hundredths to around one
tenth of an inch on average with the usual isolated heavier
amounts in the stronger convection.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Upper level ridge builds across the Mid Atlc Region Sunday
Night and Monday, and a warm front will be lifting through the
Ohio Valley and W PA. This weather feature will lead to
continued chances for showers and even a tsra - mainly in the NW
half of the area.

The deep/potent upper low (centered over the OK panhandle and
bringing snow to the southern High Plains and Southern Rockies),
will lift NE acrs the central Plains today and tonight, reaching
the Upper Glakes region late Monday night.

This dominant weather feature will shoot pieces of mid-upper
level energy well out ahead of it, which will act to trigger
isolated showers (and perhaps a few low-topped TSRA) along the
slowly northward drifting surface boundary over PA tonight
through Monday morning.

Temps should return/rise to very very warm levels on Monday.

A strong cold front (bowed out east and then south from the
approx 990 MB low over the Upper Glakes) will push east through
PA Mon into Mon night, accompanied by a round of potentially
potent showers and thunderstorms (likely reaching western half
of CWA in the afternoon and eastern half during the evening).
A narrow north/south ribbon of +3-4 sigma PWAT air along and
just ahead of the cold front will support some locally heavy
downpours and QPF up over one inch in some spots. SPC Day 2
outlook has ramped up the SVR threat with a SLGT RISK area
painted across about the western half of the CWA for Monday
afternoon and evening.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Once this front passes by much chillier air will advect into PA
on cyclonic flow with a gusty NW wind and unsettled light
showery weather, persisting mainly for the northern part of the
state right into Wednesday.

Chance for a more widespread (potentially MDT to HVY) rain
arrives Thu into Fri as latest 00Z Operational GFS/EC run and
their EFSs are coming into decent/converging agreement with an
area of low pressure progged to develop along the southern
Appalachians and the lift north-northeastward.

Although this event shows some pretty strong signals (even at
this long time range) for a potential, widespread 1-2 inch
rainfall late in the upcoming week, A wide and varying array of
models solutions has been present prior to the latest model run
or two to throw some uncertainty into the mix w/respect to the
specific timing and amount of showers across the CWA.

Fri night and Saturday will turn windy and quite cool with
isolated rain showers falling across the central mtns, while
the Alleghenies experiences more numerous rain showers (and
yes, maybe even the last gasp of show showers until later this
fall).

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...

Southeast low-level flow has brought a blanket of MVFR ceilings
from THV up into AOO and UNV. Expect these ceilings to hang
tough in the range of about 2000-3500` today while most of the
remainder of the flying area sees ceilings a little higher in
the 3000-5000` range. BFD will uncharacteristically enjoy the
best conditions with scattered clouds and VFR conditions.

Short term high resolution model consensus shows scattered
thunderstorms developing along the Alleghenies by mid afternoon
and drifting to the east into the early evening. Used VCTS
given low confidence/limited spatial coverage. Model guidance
generally shows a lowering trend in conditions tonight into
Monday and have followed this bringing most sites down to
MVFR/IFR into early Monday morning. IFR is most likely at
MDT/LNS.

Outlook...

Mon...Breezy. Showers/thunderstorms likely with periods of
sub-VFR. A few strong-severe storms possible wrn 1/2 Monday
afternoon/evening. FROPA Monday night.

Tue-Wed...Breezy with a chance of showers NW.

Thu...Widespread sub-VFR with rain likely.

&&

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

&&

$$
SYNOPSIS...La Corte/Lambert
NEAR TERM...La Corte/Lambert
SHORT TERM...Lambert
LONG TERM...Lambert/Gartner
AVIATION...La Corte/Steinbugl



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