Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 270355
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1155 PM EDT Mon Jun 26 2017

.SYNOPSIS...
A long wave trough over the Great Lakes and eastern Canada will
deepen across the region. This feature will keep it cooler than
normal into Wednesday. Scattered showers and thunderstorms will
be across the region this afternoon and evening and again on
Tuesday, especially across the northern part of the Keystone
state during the afternoon hours. A warm up and return of higher
humidity levels will occur on Thursday and Friday, as high
pressure moves off the east coast. While temperatures will
average near to above normal for the second half of the week,
there will be occasional showers and thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Showers were more widespread than expected this evening,
particularly in southern extent. Shortwave trof lifting through
east central PA late this evening is taking the bulk of activity
with it, but will need to keep slgt chc to chc pops going until
shortly past midnight in the east.

Farther west, additional upstream shortwave approaching from
central OH will keep isold to sct coverage of showers going
overnight into my western zones. Another round of nocturnal-mid-
lake-convergence-driven- convection could POP up overnight.
These may reach into the Laurels/Alleghenies by morning and have
kept low chc POPs there. It will be cooler tonight than Mon AM,
but the varying cloud cover could help keep temps up. Some fog
is possible in the valleys where they do get some rain this
evening.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Tuesday will be a similar day to Monday...but may hold a few
less showers in the aftn with the negative/suppressing influence
of the rising heights behind the strong short wave passing
overhead (and the related cloud cover and any showers) in the
morning. The afternoon heating and cool air aloft will still
generate sct showers in the nrn tier. Max temps will be similar
to Monday or even a few degs F cooler factoring in chaotic cloud
cover in the morning. On the other hand...With the length of
the daylight in late June, the sun can can overcome a late start
to cook up temps.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Trough axis moves through on Tue, with secondary trough sliding
through Tue night as high pressure builds at the surface. This
will keep just very low pops mentioned in the NW mtns during the
evening. With clearing skies, NW flow and light winds, and
dewpoints in the mid 40s to lower 50s, Wed morning will be the
chilliest one of the week as lows should drop to near dewpoints.
With plenty of sun, temps will rebound during the day back into
the 70s.

As the high moves off the east coast by Thursday, a warm front
will lift across PA ushering in a southwest flow of warmer and
noticeably more humid air. Lows Thu morning will be about 10F
warmer than the day before, and daytime highs will bump up about
4-8F as well.

Upper flow becomes zonal late week as a surface low tracks
across the northern Great Lakes and southern Canada, which will
focus a stationary front across that region. We`ll remain on the
warm/humid side of that boundary (as highs rise to near 80 NW
and 90 SE along with muggy overnight), and see convective
activity increase Thu heading in the weekend - with highest
likelihood over the NW. Convection will be more scattered over
the SE.

Active pattern continues Sun into Mon as another low rides along
the persistent frontal boundary to our west and north, finally
nudging that front into/through PA and keeping mention of
showers in the forecast while taking some of the edge off of
the above normal temps.

&&

.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Main concern overnight will be at BFD and MDT, where wet
ground from earlier showers, combined with clearing skies and
light wind, could result in fog. For now, am banking on just
enough of a breeze to preclude significant fog issues, but will
be monitoring for possible low visibilities after midnight.
Based on radar trends and near term model data at 04Z, still
can`t rule out a shower at LNS until about 07Z. If a shower
occurs there, then LNS will also be at risk for fog late tonight.
Elsewhere, confidence is high for widespread VFR conditions for
most of the night.

A weak frontal boundary will push through the region early
Tuesday morning, accompanied by a few showers. Lack of moisture
with this system should translate to a continuation of VFR
conditions for much of central Pa. Any patchy fog should mix out
by around 13Z. High pressure and associated dry air mass will
build into the region later Tuesday, accompanied by widespread
VFR conditions.

.OUTLOOK...

Wed...No sig wx expected.

Thu-Fri...Isolated PM tsra impacts poss, mainly northern Pa.

Sat...Scattered PM tsra impacts possible.

&&

.EQUIPMENT...
KCCX radar is back on line and in normal operation.

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo/DeVoir
SHORT TERM...Dangelo
LONG TERM...RXR
AVIATION...Fitzgerald
EQUIPMENT...



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