-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 261948
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
348 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 11 PM THIS EVENING/...
Dewpoints have dropped back into the 40s over the entire area
this afternoon with deep mixing. Temps aloft are chilly for
late June and have allow an expansive cu field to pop. Only a
few places of which look like moderate or towering cu have been
able to grow - probably due to the lack of moisture. There is
also a lack of a trigger to make the low level kick necessary to
overcome any CIN. The earlier boundaries from the over-lake
convergence are likely what is still helping to puff up the
storms in the NW. Coverage will be greatest in the nrn mtns
where 70-80 POPs have been painted. Timing will be centered
around 21-22Z in the NC/Cent mtns with a bell curve around then
earlier in the NW and later in the NE/EC counties. Showers
should diminish with loss of heating but they could linger a few
hours after sunset in the NE/Poconos.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Another round of nocturnal-mid-lake-convergence-driven-
convection could POP up overnight. But, guidance also whips a
strong short wave trough through the upper Great Lakes and
pushes showers and thunderstorms over the second half of the
night into wrn PA. These may reach into the Laurels/Alleghenies
by morning and have placed low chc POPs there. It will likely
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.

Tuesday 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/...
-- Changed Discussion --
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
noticably 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.
-- End Changed Discussion --

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
line of SHRA/TSRA over the nrn tier is along a weak boundary
which used to lie over the lower lakes this morning. The
convergence is drifting to the east and a short wave trough over
OH could add a little forcing to the mix this aftn/evening. But,
most of these shra will be diurnally driven, and will die as the
heating goes away. The nrn mtns will have numerous SHRA/TSRA
until about 00Z when the weak trough aloft scoots to the east.
A tail of showers may linger in the NE and even into the central
mtns through 01Z or 02Z. The clearing behind these showers and
light wind may allow fog to form again in the northern valleys
by sunrise. But there are some clouds which will move in later
tonight.

Next issue will be a much stronger trough aloft whipping around
the base of the larger/long wave trough. The timing of the best
lift provided by this wave will be before sunrise over the west.
But, the remnants/moisture associated with this wave will still
make some isold/sct shra over the local through the morning.
Limits to vsby will be few, though. Just isold/sct SHRA are
then expected for just the nrn mtns/KBFD in the aftn.

.OUTLOOK...

Wed...VFR.

Thu...VFR early, then sct afternoon SHRA/TSRA NW.

Thu PM-Sat...sct-nmrs SHRA/TSRA.

&&

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

&&

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

&&

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