Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 181436
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1036 AM EDT Tue Sep 18 2018

.SYNOPSIS...
The final remnants of Tropical Depression Florence will track
east of the region later today. Occasional moderate rain
showers will exit portions of the Lower Susquehanna River Valley
this afternoon. Improving conditions with diminishing showers
will gradually develop from west to east across the region this
afternoon and tonight.

Dry weather is expected Wednesday and Thursday before the next
opportunity for rain showers arrives with a cold frontal
passage Friday afternoon and night.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Stable stratus covers much of the northwest half of PA mid to
late morning, while slow moving showers with some moderate
intensities are tracking across the southeast third. Seeing some
continued development and training over Lancaster County
presently so will keep the Flood Watch going through Noon today.

PWATs drop by about half by this evening across practically all
of the CWA with the thick, layered clouds associated with
Florence and her trailing weak cfront sliding east of the region
by the afternoon hours across the western half of the state.

For the bulk of the region this afternoon, expect brightening
skies with periods of sunshine through shallow strato cu, winds
veering to the NNW and gusting into the teens and dewpoints
falling into the more comfortable lower and middle 60s.

Max temperatures today will be in the mid to upper 70s in most
locations.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Winds diminish tonight and stay relatively light for Wednesday
through most or all of Wednesday night as a ridge of high
pressure slides east across the Commonwealth. Expect any morning
fog and stratus/stratocu to dissipate after 15Z leaving mostly
sunny conditions with just some scattered fair weather cu.

Low temps tonight (with patchy dense valley fog twd daybreak
across the western half of the region) will vary form the upper
50s in the perennial cold spots across the NW mtns, to the mid
60s in the SE.

Afternoon highs Wednesday will vary from the lower 70s across
the northern mtns, to the lower 80s in the southern valleys.
These readings will be some 5-8 deg F above normal for mid
September.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Wednesday night into Thursday will be dry, along with much of
Friday. Main concern/impact weather for early in the extended
period will come in the form of areas of dense valley fog
between about 08-14Z Thursday, thanks to light wind partly
cloudy skies and sfc temps cooling well into the 50s into the
valleys of Central and Northern PA.

Temps and dewpoints moderate Thursday into Friday given the high
pressure ridge drifting east of the region on thursday and a
brisk southwest flow developing by Friday. We have not seen
much southwest or west flow this summer, but rather clammy
easterly flow much of the season.

A cold front moves southeastward into the area late Friday.
After some showers and storms late Friday, the first part of
the weekend looks to be dry.

Still have a chance of showers in on Sunday into early Monday,
as the warm air returns, before the next cold front.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Showers will cover the southeast third to half of PA this
morning. Widespread MVFR/IFR reductions will persist into
midday, before improvement to VFR this afternoon as winds
transition around to the N/NW. MVFR to VFR expected northwest
half of PA.

MVFR develops tonight in upslope flow over the western/northern
higher terrain with patchy fog elsewhere. Dry weather is
expected Wednesday and Thursday before the next opportunity for
rain showers arrives with a cold frontal passage Friday
afternoon and night.

.Outlook...

Wed-Thu...Overnight cig reductions north/west. Morning fog
poss. Otherwise no sig wx.

Fri...Fair early. SHRA/TSRA aftn/eve. CFROPA late.

Sat...Overnight cig reductions north/west. Morning fog poss.
Otherwise no sig wx.

&&

.HYDROLOGY...
The latest guidance from OHRFC and MARFC keep all river points
below flood stage. Several points are forecast to exceed action
or caution levels. Will need to monitor rainfall very closely
with streams running very high.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until noon EDT today for PAZ057>059-065-066.

&&

$$
SYNOPSIS...DeVoir/Lambert
NEAR TERM...DeVoir/Lambert
SHORT TERM...Lambert
LONG TERM...Martin
AVIATION...DeVoir/RXR
HYDROLOGY...


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