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000
FXUS61 KCTP 182006
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
306 PM EST Mon Feb 18 2019

.SYNOPSIS...
Colder air aloft pushed into the region today, bringing snow
showers with an additional coating of snow across the northern
and western mountains of the state. A large area of high
pressure over the northern Plains States will move southeast and
become centered over the state late Tuesday. A deep trough of
low pressure over the Rockies and Southwest U.S. will eject a
piece of moisture laden energy across the Southern Mississippi
and Tennessee Valleys Tuesday and Tuesday night. This moisture
will ride up and over the dome of colder air in place across the
Northeast U.S. and bring snow then a wintry mix of
precipitation for Wednesday into Wednesday night. Mainly dry and
milder air will follow for the end of the week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Colder air moving in aloft in the wake of the weak storm that
brought some light snow accumulations (followed by a coating of
ice from freezing rain) late Sunday into early this morning,
will bring a light additional coating of snow across the
northern and western mtns of the state through late this
afternoon (where mean cloud- layer temps were in the warmer half
of the DGZ thermal ribbon - generally between
-12 and -15C). Elsewhere, just some flurries fly across the
 Central Ridge and Valley region of the state. skies will be
 mainly OVC through the afternoon, followed by gradual clearing
 early tonight across the Lower and Mid Susq Valley, and partial
 clearing late tonight over the remainder of the Forecast Area.

1930Z Temps are right around forecast max values - in the low
to mid 20s across the northern tier counties, the upper 20s to
lower 30s along the Allegheny, and upper 30s to low 40s in the
SE.

Northwest winds will continue to gust into the upper teens and
mid 20s (KTS) into this evening before veering about 20-30
degrees and decreasing by 5 kts or so late tonight and early
Tuesday.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Much of the area will be clear by Tuesday morning, though RAP
soundings indicate that some patchy thin and low stratocu are
possible across the Northern Mtns of PA.

The Center of a sprawling area of high pressure covering the
NErn half of the CONUS will be centered over New York and PA.

However, low pressure will gather over the lower MS Valley Late
Tuesday and Tuesday night with a strong southerly flow of WAA
and Gulf Moisture out ahead of it, leading to a rapidly
blossoming area of Precip across Tennessee and Lower/Mid Ohio
River Valleys.

The leading edge of this precipitation shield (in the form of
snow) will move quickly up the OH River Valley and should start
in the Laurels up to a few hours before sunrise Wednesday, and
spread north and east to the Central Mtns and Susq Valley
between 11-14Z.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Uncertainty is very high at this point as to the evolution of
precip type and the QPF over PA on Wed. GEFS and SREF plumes
play out a QPF range from just a tenth or so to many inches.
The temps also range wildly. The GFS warms everyone in Central
PA up to plain rain during the day, while the NAM and EC keep it
much colder. Will keep mentioning the storm in the HWO, but not
enough confidence in many aspects to post a watch. Most likely
place to get the worst impacts will be along and S of the PA
Turnpike.

Prev...
For Wed, low pressure lifting northeast across the Great Lakes
will result in some snow, given warm advection. By late morning
and early afternoon, looks like sleet and freezing rain would
mix with the snow. This based on thickness coming up fast, as
the system is weaker and faster than the one we had last week.
Thus did not hit the snow real hard, and did not want to go too
high on ice. This in part due to QPF on NAM across the far south
was looking too high. Other models have the .25 inch line just
brushing the far south. Hard to see much more than .25 in any 6
hour period. The NAM had .75 inches across the south in a 6 hour
window.

This event looks like the event last week, most of the precipitation
would be east of the area by Midnight.

For most of the period from Thursday into at least early Saturday,
not a lot going on. I did cut back on POPS and weather where I
could. Temperatures borderline, so used a mix of rain and snow.

Main question is if a deep low will form and lift across the
lower Great Lakes on Sunday. For now, went close to the
superblend. EC and GFS runs not close. GFS has much weaker
systems. If EC was to verify, Monday would be the first real
windy day of the late Winter, early Spring season.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
MVFR Cigs will continue into this evening across much of the
Central and Western parts of the CWA, with areas of IFR Cigs and
MVFR VSBYS in snow showers across portions of the NW mtns and
Laurel Highlands.

Model soundings indicate there will be lingering MVFR stratocu
across the mountains of central Pa, while downsloping flow
yields a return to VFR conditions in the Susquehanna Valley from
KIPT south through KMDT/KLNS.

Southeast of a KAOO to KSEG and KAVP line, sky cover will be
generally BKN in the VFR - 3500-4500 FT AGL range along with
widespread VFR VSBYS.

A moderately tight pressure gradient behind the departing storm
will produce gusty west-northwest winds for the rest of today
across southern PA. Bufkit soundings support gusts ranging from
27-34KTS from KJST to KMDT and KLNS through about 01Z Tuesday,
before winds and gusts decrease by 5-10 KTS.

Outlook...

Tue...VFR.

Wed...Snow to a Wintry mix.

Thu...AM light freezing rain/low cigs possible.

Fri...No sig wx expected.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday morning through Thursday
morning for PAZ058.
Winter Storm Watch from late Tuesday night through late
Wednesday night for PAZ024>026-033>036.
Winter Storm Watch from Wednesday morning through Thursday
morning for PAZ027-028-056-057-059-063>066.

&&

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