High Wind Watch 1, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
1243 AM EST Mon Jan 8 2024

.SYNOPSIS...
An upper level trough will shift east of the region tonight and
high pressure will build in Monday. An intensifying, moisture-
laden low pressure system will move Northeast across the Ohio
Valley and the Great Lakes region late Tuesday into Wednesday
bringing a brief period of snow at the onset, then widespread
moderate to heavy rain and wind that will lead to a threat of
small stream and creek flooding. Another storm lifting north
from the Gulf Coast could affect the region by the close of the
work week.

&&

.NEAR TERM /UNTIL 7 AM THIS MORNING/...
Light, lake enhanced, orographic snow continues to fall late this
evening over the Allegheny Plateau. Model qpf supports up to an
additional inch over the snowbelt of northwest Warren County
overnight and 1-2 inches where orographic forcing is greatest on
the highest ridges of the Laurel Highlands. Passage of the
upper trough and approach of surface ridging will result in
falling inversion heights and diminishing snow showers
overnight. As cloud depths become more shallow, modeled cloud
top temps rise above -10C, indicating spotty -fzdz is possible
over parts of the Alleghenies overnight. However, significant
travel impacts are not anticipated, as any fzdz will either fall
on snow covered, or wet/treated roads.

Downsloping subsidence is already producing breaks in the
overcast this evening east of the Alleghenies and model RH
profiles indicate this slow clearing trend will continue east of
the mountains, while overcast skies persist through dawn over
the NW Mtns and Laurels.

Weak cold advection will push readings slowly downward
overnight, with min temps in the upper 20s and low 30s.

&&

.SHORT TERM /7 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Ridging at the surface and aloft will bring fair and mild
weather with light winds Monday. However, low level moisture
trapped beneath a subsidence inversion should result in stubborn
low clouds across the Alleghenies and especially the NW Mtn,
where SREF prob charts and model soundings indicate clouds will
remain all day.

Light wind and limited mixing, combined with snow cover, should
keep temperatures from rising much Monday, despite mainly sunny
skies east of the mountains. See no reason to deviated from NBM
temps, which peak in the 30s over much of Central PA and in the
low 40s in the Susq Valley.

Conditions currently look favorable for efficient radiational
cooling Monday evening, with mostly clear skies and light wind,
so have undercut min temps slightly. Increasing cirrus and a
developing southeast breeze ahead of an upstream trough should
cause readings to bottom out during late evening, then rise
late Monday night.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The focus for the next few days will be on a potent southern
stream trough lifting out of the Southern Plains. All medium
range guidance tracks this feature and the associated deepening
surface low west of PA through the Grt Lks Tuesday PM into
Wednesday. A blocking high over New England may supply enough
cold air for an initial wintry mix. However, max wet bulb temps
aloft rise well above 0C by Tuesday evening, as an anomalous
(+4SD) southerly low level jet pivots through the state.

A deep plume of GOMEX moisture overrunning the retreating low
level stable airmass should result in a moderate to heavy
rainfall late Tuesday, with an accompanying flood risk lasting
into Wednesday. Latest ensemble prob charts indicate the
eastern half of the forecast area will be most susceptible with
amounts in excess of 2 inches possible, combined with melting
snow. MMEFS (NAEFS and GEFS) shows numerous river points across
the eastern part of the forecast area with 30-70% prob of
reaching minor flood stages by Wed AM. Current MARFC forecasts
take a couple tributary points above flood state on Wednesday.
The most vulnerable locations will be the Lower Susquehanna
Mainstem and tributaries (i.e. Conodoguinet Creek, Swatara
Creek, and Sherman Creek).

Strong, gusty winds will be a concern for parts of Central PA
on Tuesday into Wednesday as the surface low bombs out across
the Great Lakes. Gradient winds ahead of the approaching low
will produce strong southeasterly winds across the higher
elevations in the Laurels and northern mountains Tuesday. Gusty
winds are also possible across southeast PA, where guidance
indicates the potential of breaking into the warm sector ahead
of an approaching occluded front Tuesday evening. Current EPS
guidance indicates 40kt+ gusts are likely Tuesday PM across the
aforementioned zones (everywhere except the central ridge/valley
region), with 50 kt gusts not out of the question.

Scattered snow showers are likely to accompany the passage of
the upper low Wed morning, mainly over the Allegheny Plateau.
Subsidence behind this feature, combined with a tight pressure
gradient south of the deep surface cyclone, should result in
another period of strong winds Wednesday afternoon. Latest EPS
plumes indicate gusts could again near advisory criteria.

Diminishing winds and fair weather appear likely by Thursday,
as the low lifts away and surface ridging builds into PA. Zonal
flow is progged to flood the lower CONUS with relatively mild
Pacific air late next week, so expect temps to be several
degrees above average. Latest GEFS and EPS both track another
deepening low pressure system west of PA late next week. This
scenario favors another mainly rain event Friday PM, with a
possible initial wintry mix over the central mountains of PA.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A moist airmass at low levels will keep IFR and MVFR conditions
over the western half of the area into the morning while eastern
sites will remain VFR. Some guidance suggests that IPT could
briefly see MVFR ceilings at times through 12Z, but with the
HREF only suggesting a 20-30% chance of this occurring, decided
to keep them VFR.

Conditions improve on Monday, as a ridge of high pressure moves
east of the area. Snow showers will come to an end at JST around
12Z at which point cigs/vsby will gradually improve. All sites
will likely see a period of VFR conditions during the late
afternoon before winds become more southerly and low level
moisture begins to increase once again ahead of the next low
pressure system. Mid and high clouds will begin to overspread
central Pennsylvania after 00Z Tuesday, but at least some MVFR
cigs cannot be ruled out across the southern tier as well. All
precipitation looks to hold off until after 06Z.

Outlook...

Tue...Windy. VFR early with snow and rain and widespread
restrictions arriving toward daybreak.

Wed...Quite breezy. Gradually improving conditions.

Thu...Dry weather with mainly VFR conditions.

Fri...VFR conditions early, then rain and snow developing.

&&

.HYDROLOGY...
1.5 to 2.5+ inches of rain is forecast next Tuesday into
Wednesday over eastern Pennsylvania. There will be a risk of
areal and river (small stream) flooding due to the combination
of forecast rainfall, snow melt, saturated ground, and the
associated enhanced runoff during the cold season. Ensemble data
is already highlighting the potential for widespread rises to
action with at least a 30% chance to exceed minor to moderate
flood stage, esp the Swatara Creek basin and the other large
tributaries to the lower mainstem Susq.

The Weather Prediction Center has placed eastern PA in a
Moderate Risk of Excessive Rainfall and the Slight Risk extends
into the Lower Susquehanna Valley. Moderate Risks are quite rare
in Central PA (only 4 per year on average). They are even more
rare during the month of January with only 2 occurring in
Central PA since 2010 (24 January 2010 and 30 January 2013).

&&

.CLIMATE...
Harrisburg got 3.3" SF yesterday (1/6/24), ending the snow
drought there. After 345 days, they finally got more than a
trace of snow. That is the longest stretch of snowless weather
since records began in 1888.

Similarly, State College reported 5.0" SF this morning (7AM -
7AM climate site). It was the first time in 346 days they
measured at least 1 inch of snow. The streak of 345 consecutive
days without at least 1 inch of snow was the longest on record
breaking the previous record of 319 days from 2/20/1979 -
1/4/1980 that was tied from 3/16/2006 - 1/28/2007.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 AM EST early this morning for
PAZ033.

&&

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald/Banghoff
AVIATION...Martin/Bauco
HYDROLOGY...Banghoff
CLIMATE...Dangelo

Preliminary Local Storm Report
National Weather Service State College PA
1012 PM EST Sun Jan 7 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 AM     Snow             Pleasant Gap            40.86N 77.73W
01/07/2024  M4.7 inch        Centre             PA   NWS Employee

&&

MRC

Preliminary Local Storm Report
National Weather Service State College PA
1017 PM EST Sun Jan 7 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1159 PM     Snow             Harrisburg Intl Airport 40.20N 76.76W
01/06/2024  M3.3 inch        Dauphin            PA   Official NWS Obs

&&

MRC

Preliminary Local Storm Report
National Weather Service State College PA
1024 PM EST Sun Jan 7 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     Snow             Montoursville           41.25N 76.92W
01/07/2024  M4.5 inch        Lycoming           PA   Official NWS Obs

&&

MRC