Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 231507
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1007 AM EST Fri Feb 23 2018

.SYNOPSIS...
A nearly stationary frontal boundary will remain just south of
out Pennsylvania through Saturday, before lifting north across
the commonwealth as a warm front Saturday night. A cold front
will ultimately usher in cooler and drier air Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Areas of drizzle and pockets of freezing drizzle will remain a
concern over the higher terrain of northeast PA this morning.
Mesonet continues to show temperatures between 31-32F over the
higher elevations of north central Pa and HRRR and SREF temp
plumes indicate steady or even slowly falling readings through
12z.

Ribbon of higher deep layer moisture extends from the Lower
Mississippi Valley into the Ohio Valley...eastward along and
south of the Mason Dixon line to the offshore mid Atlantic
waters, where PW is between 1.0" and 1.25". Shortwave cresting
the upper ridge is maintaining showers along the PA/MD border
eastward to the southeast Piedmont this morning. HRRR tracks
these offshore by mid morning, as the next slug of moisture
arrives from the Ohio Valley.

The next wave/batch of rain should is still timed into the
Alleghenies by 13z this morning, and into the Central Mountains
by 15z-16z. All but the Lower Susq will see showers by late
morning, but even the Lower Susq. should see likely POPs by
early afternoon as robust PW approaching 1.25" surges ENE.
Meanwhile, over the high terrain of northeast Pa, temperatures
are expected to remain around the freezing mark through at least
midday, so will maintain the winter weather advisory up there
through noon. Latest NBM indicates a change to rain in most
areas Friday afternoon. However, the normally colder HREFV2
keeps some of the northeast ridgetops below freezing into this
evening.

Plain rain to fall everywhere else as temperatures hold steady
in the mid 30s to low- mid 40s. Expect a very small diurnal
variation east of the Alleghenies due to CAD, while milder air
surges into far SW PA.

Steadiest and heaviest rainfall diminishes late this
afternoon/early this evening. It will be a cool and damp
overnight with areas of fog and drizzle.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
After a lull in the precip tonight in between waves, the focus
this weekend will shift to potential flooding, with additional
waves of moderate to locally heavy rain moving over the area
through Sunday.

PW again surges to between 1.0" and 1.33" late Saturday through
Sunday morning as an energetic upper wave and frontal system
slice across the region. Flood watch remains in effect for
western and central sections through Sunday evening, as we
expect significant rises on streams, creeks and river tribs
with streamflows already above normal. The ground/soil is nearly
saturated so the risk for widespread minor river flooding, along
with poor drainage/low- lying flooding is certainly in play.
Temperatures will slowly rise but should eventually reach the
50s and low 60s by Sunday based on multi model consensus blend.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The wet pattern looks like it will take a break during the first
part of next week before precip risk increases Wed-Fri.
Temperatures should continue to run above average for late
February.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...

A stationary boundary just south of the MD border will provide
the focus for periods of rain and drizzle into Sunday.

Expect widespread IFR conditions to continue at least into
Friday. A strong SW LLJ will provide the potential for some
LLWS this afternoon into the overnight.



Outlook...

Fri...Widespread restrictions in periods of rain. Some
improvement poss SW late.

Sat...Widespread restrictions with rain.

Sun...Widespread restrictions likely in periods of rain.

Mon-Tue...No sig wx.

&&

.HYDROLOGY...
Active hydrologic pattern through Sunday. Recent snow melt and
rainfall has soils quite wet. Streamflows are also running
high. Recent rainfall has stream flows above average. So focus
will turn to where the heaviest rain falls and if it is heavy
enough to produce flooding. Models consistent with heaviest rain
west of the CWA but still close enough to keep a flood threat
over the western half of the CWA. Issued a Flood Watch for this
area to address the threat. Right now no river forecast to
flood, but expect significant rises and will monitor closely.
Some poor drainage and small stream flooding is likely.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday evening for PAZ004>006-010>012-
017>019-024>026-033>035-045.
Winter Weather Advisory until noon EST today for PAZ006-037-
041-042-058.

&&

$$
SYNOPSIS...DeVoir/La Corte
NEAR TERM...DeVoir/La Corte
SHORT TERM...DeVoir/Steinbugl
LONG TERM...DeVoir/Steinbugl
AVIATION...La Corte/Ceru
HYDROLOGY...



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