Area Forecast Discussion
Issued by NWS State College, PA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS61 KCTP 211746
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
146 PM EDT THU JUL 21 2016

.SYNOPSIS...

Pennsylvania will be on the northern edge of a subtropical ridge
into next week. A couple of weakening cold fronts will pass
through the area Friday and again on Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...

High pressure will move off the Mid Atlantic coast
today...allowing return sw flow to advect warmer and eventually
more humid air into the state. Large scale subsidence and a dry
airmass in place will ensure another dry day with abundant
sunshine. GEFS mean 8h temps of around 18C will translate to max
temps from the mid 80s over the high terrain of the north and west
to around 90 in the valleys.

The overnight will begin dry before remnant convection from an MCS
currently diving through the Central Gr Lakes makes a run at my
NWRN zones. We should remain dry through late evening with the
chances for rain start to ramp up from midnight onward.

&&

.SHORT TERM /FRIDAY/...

Shortwave topping the ridge into the nw flow aloft will advect
increasing moisture/instability into the region later tonight and
Friday. Ensembles point to an increase in the PWATs ahead of the
shortwave and associated weakening cold front.

00Z NCAR ensemble supports the idea of a dying line of
thunderstorms working into the nw mountains during the few hours
either side of sunrise as the parent shortwave and best large
scale forcing pass well north of the state.

During the day the weakening cold front will be battling high
heights aloft as it drops se into the region.

After the early day activity fades, diurnal heating and weak
convergence with the dying front will bring the chance for
additional showers/thunder mainly during the mid day and afternoon
hours and mainly over northern areas. Deterministic
guidance shows mid level temperatures on the order of 9-11C which
will act as a convective deterrent, limiting the extent of
development and doing little to break the recent extended period
of widespread dry conditions we have been experiencing.

00Z NCAR ensemble data indicates the best chance for late day
thunderstorms will be across northeast Pa, closest to trailing
shortwave tracking across upstate NY. SPC has placed nearly all of
central Pa in a marginal risk area Friday, but with the expected
warm mid levels, thinking is that convective activity will be
widely scattered with the very far north being most susceptible
to a few strong storms.

8h temps rising to near 20C should translate to max temps from
the m/u80s over the Alleghenies, to 90-95F elsewhere. The heat,
combined with rising dewpoints, should result in widespread heat
indices in the 90s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Big story in the extended fcst is expected heat wave lasting into
early next week, as axis of subtropical ridge briefly shifts from
the plains to the northeast conus. Anomalous upper lvl ridging
building over PA should bring hot and mainly dry wx this weekend,
as warm temps aloft suppress convection. Next chance of shra/tsra
for most of the area comes Monday ahead of shortwave working
across the Great Lakes. Any rainfall Monday is likely to do little
to stem the dry pattern we have been in. Latest GEFS mean qpf is
only a couple tenths of an inch Monday.

00Z ECENS/NAEFS mean 8h temps are near 20C Saturday through
Monday, indicating the potential of several days in a row with
highs in the 90s in the valleys. Heat indices around 100F appear
possible by Mon across the Susq Valley, as higher dewpoints are
advected into the area. Overnight lows are also a concern as the
area doesn`t cool off at night through the weekend with Southern
PA lows in the 70s. Some modest cooling appears likely by Tue/Wed
of next week behind weak cold front. However, temps still likely
to remain somewhat abv normal within a generally zonal flow.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...

Mainly VFR expected through at least Friday.

An area of showers/thunderstorms is expected to impact the far
northwest airspace between 06-12z tonight with localized
restrictions possible.

Isolated to widely scattered thunderstorms are possible across
the entire airspace Friday into Friday night.

OUTLOOK...

SAT-SUN...Early morning fog possible...otherwise no sig wx.

MON-TUE...Restrictions possible with a chance of
showers/thunderstorms.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...La Corte
LONG TERM...Fitzgerald/Ceru
AVIATION...La Corte



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.