Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 181522
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1022 AM EST Thu Jan 18 2018

.SYNOPSIS...

A large are of high pressure centered over the Lower Mississippi
Valley will maintain fair skies for the next few days.
Temperatures will moderate to near normal Friday, then climb
well above normal over the upcoming weekend with mainly dry
weather continuing. The next chance for widespread rain showers
will come Monday into Tuesday with the passage of a cold front.

&&

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

GOES16 visual loop shows a shield of low clouds creeping down
over my northern counties. It appears to be associated with a
very weak back door cold front/surface trough.

The remainder of the region is just cold and dry with some thin
mainly low clouds.

Model soundings show these clouds are occupying the thermal
channel of -12 to -18C, which is right in the middle of the
prime Dendritic Growth Zone. We see confirmation of this with
some very light snow occasionally being reported at KJST and we
had a report of freezing drizzle along a very small section of
I-80. Flurries from this cloud layer are possible through mid
day before temps warm and the layer mixes out a bit.

Later on and elsewhere today, periods of sct-bkn altocu and
cirrus will spill southeast from the glakes as deep layer warm
advection begin with the slow departure of the anomalously deep,
snow-producing sfc and upper low near the Outer Banks.

Highs this afternoon will be about 5 deg F below normal, and
range from near 20F across the NW mtns to the L30s in the
Southeast. Westerly winds will freshen to 10 to 15 kts today,
with gusts in the 25 to 30 kts range later this morning and this
afternoon over the higher terrain of SC and SW PA. Relatively
lighter winds will occur across the eastern zones.

The wind will create a wind chill 15 to 20 degrees F lower than
the actual air temp through today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Variable amounts of mainly mid and high clouds along with dry
conditions will prevail tonight. A slightly lighter westerly
breeze with significantly lower gusts will result in wind chills
staying steady (or rising slightly) into tonight.

Lows tonight will be in the teens, to near 20F in the southern
PA valleys.

Mid and high clouds increase a bit Friday as do temps, that will
climb to slightly above normal highs.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
High pressure moving off the southeast coast late in the week
will bring mild and dry weather to the area which will last
through most or all of the upcoming weekend.

A deep low will swing a cold front across the area late Monday
and early Tuesday next week, accompanied by a few period of rain
showers amounting to 1 to 3 tenths of an inch of Liq Equiv
precip. There is a low probability for a weak wave of low
pressure to develop along the front heading into Tuesday which
could add a few to svrl tenths more and even some light accums
of snow.

Mainly dry weather with just some isolated to scattered snow
showers will follow for Tuesday and Wednesday, with temps
falling to a few deg below normal by the middle of next week.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...

A shield of MVFR strato-cu has crept into my northern higher
elevations associated with a weak back door cold front.

The strong gradient that is bringing the drier air and clearing
skies will allow for a period of LLWS to the region.

Most of the flying area will remain VFR into Friday as high
pressure noses in from the SW.

Outlook...

Fri-Sun...Mainly VFR.

Mon...Reduced conditions with rain showers associated with an
approaching cold front.

&&

.HYDROLOGY...
The threat of ice jamming is diminishing. Dry and colder
weather into mid week will form additional ice as stream flows
and open channels decrease. Another warm up is expected by the
end of the week into the weekend with rain to accompany a
frontal system early next week. Dewpoints not fcst to be as
high as last Friday evening, so expecting less rain and runoff.

&&

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

&&

$$
SYNOPSIS...Lambert
NEAR TERM...La Corte/Lambert
SHORT TERM...La Corte/Lambert
LONG TERM...Lambert/Martin
AVIATION...La Corte/Ceru
HYDROLOGY...


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