Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 220740
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
340 AM EDT Tue Aug 22 2017

.SYNOPSIS...
A strong cold front will move through the region late today and
early tonight. Much cooler and drier conditions will return for
the second half of the week. Temperatures will average a few
degrees below normal highs starting tomorrow and lasting into
early next week.

&&

.NEAR TERM /THROUGH TODAY/...
A few speckles on radar continue to slide eastward. The rest of
the overnight should be rain-free - but not very dry.

The high dewpoints out there now will mean that a good supply of
moisture will be in place in the low levels as the cold front
over the Upper Midwest nears late today. PWATs rise above 2" and
the the trough aloft will dig hard with 5H height falls of
12dam over the next 24 hrs. The storms over IN/IL/MO are along a
strong short wave trough. Ol` fashioned extrapolation puts
those storms/showers associated with the forcing into our NW
zones during the middle of the morning.

Most models do bring in some SHRA before noon in the NW while
the rest of the area cooks under the power of our nearest star.
No moon in the way to cool us down in the middle of the day
today. By the middle of the afternoon, CAPEs poke above 1000
J/kg, by sunset some places may be closer to 2000 than 1000.
Effective shear climbs into the 35-45KT range. The hodograph
looks like an open parachute and will create a threat of
supercells and all that is bad about them. SPC paints the threat
for tornadoes higher over our NE zones today. The EHI and Sig
Tor parameter are highest/worst in the far NW in the early aftn
and then again in the far SErn zones just before/around sunset.
LCLs will be low in the NW ~1500ft coincident with the high EHI,
but will be >2500ft later in the day over the SE. Also, CAPEs
will be lower in the NW, but much higher (perhaps as high as
3000 J/kg) in the SE. In between the NW and SE maxima things
look they would be organized into more-linear storms with the
predominant threat wind damage.

Will carry catg POPs for the day over the NW and central zones,
but keep them lower than 80 in the SE, since the storms may not
get there/develop overhead until close to or after sunset.

Maxes will be very warm for this time of year with maxes 5-10F
above normal.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
On-going convection will be entering the SE third of the area
around 00z per most guidance. Some cells may pop up ahead of
the main area/line of storms due to the very high CAPEs - but
some mid-level capping/lapse rates will try to suppress deep
convection as long as it can. Will make high-likely to lower
categorical POPs for the SE half of the area after 00z, but
kill most of the convection around midnight. The real cold front
will likely move through in the middle of the night, so some
SHRA may linger behind the main show. The front should clear the
area before sunrise. Dewpoints will be crashing in the wake of
the cold front. Mins will be in the m50s in the NW, but still
in the l70s SE.

Some instability under the upper trough and with a lake breeze
could pop some SHRA close to the lower lakes and drift would
bring them south. Will keep POPs below mentionable except in the
NW 3 zones. Maxes on Wed will be near normal in the east/valleys,
but about 5F below normal in the mountains.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
An extended period of early autumn-like weather starts
Wednesday and lasts into the upcoming weekend as an anomalously
deep sfc low/upper trough slides east across southeastern
Canada.

Daytime high temps will be about 5-7 Deg F below normal across
the Western Mtns on Wednesday, though still just slightly below
normal across the SE zones prior to the arrival of the
deeper/colder air for the latter part of the week.

GEFS mean 850 mb temps will dip about 2-3 deg C in all locations
for Thursday-Sunday, leading to max temps averaging 5-10 F
below normal (with min temp departures about 10-13F below
normal Friday-Sunday) as a large Canadian High Pressure area
pushes SE across the Glakes Region and becomes centered over the
NE states.

Lows Fri/Sat/Sun mornings with high centered overhead will be
dipping into the l-m 40s over the Northern Mountains (and deeper
valleys of the Central Mountains) and solidly into the 50s
elsewhere. Some of the perennial cold spots near and to the east
of KBFD could see readings of 38 or 39F.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Only a few showers left across the far northeast now.

06Z TAFS adjusted and sent.

Areas of fog beginning to develop, with a few areas of LIFR
already being reported at KIPT.

Overnight, expect widespread MVFR fog, with areas of IFR/LIFR
visibilities and ceilings.

Morning fog gives way to VFR conditions later this morning, but
widespread TSRA expected during the afternoon and evening, as a
strong cold front moves into the area.

.OUTLOOK...

Wed...AM low cigs BFD/JST, otherwise VFR.
Thu-Sat...No sig wx expected.

&&

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

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...La Corte/Lambert
AVIATION...Jung/Martin



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