Latest Area Forecast Discussion for Central PA

Here is the latest Area Forecast Discussion for Central PA

This text statement is the latest forecast reasoning from the NWS in State College, PA

See the links at the bottom of the page for previous issuances/versions of the statement as well as our other text statements.

533
FXUS61 KCTP 021140
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
640 AM EST Mon Mar 2 2026

.WHAT HAS CHANGED...
* Posted winter weather advisory for freezing rain for almost
all of the forecast/warning area for later tonight and
Tuesday morning.

&&

.KEY MESSAGES...
1) A light wintry mix with light freezing rain accumulations
likely late Monday night into Tuesday morning.

2) Periods of rain with temperatures very much above normal
Wed onward.

&&

.DISCUSSION...
KEY MESSAGE 1: A light wintry mix with light freezing rain
accumulations expected later tonight into Tuesday morning.

Over the past 24 hours, the model solutions have come into
better alignment w.r.t. timing. The QPF and temperatures have
been very consistent from run to run. P-type will be a varied
mix at first, but the gradual warming aloft will turn the
precip to liquid. The consistency has raised our confidence in
a light glaze of ice occurring late tonight and Tuesday morning.

We wondered whether it is a little early to post the advisory
at this range (24-30hrs before start of the hazardous wx). But,
the forecast has been highly consistent at painting measurable
amounts of ZR over the entire CWA. WPC guidance, FRAM progs from
HREF, and NBM forecasts all add together to make a high
confidence forecast for a thin glaze of ice accretion in most
places. We kept the goalposts wide on timing, that is, erring a
little early on start of the ZR, and a little later than when
the ZR should be done in each area. This should help our
partners to be ready should it move in a little faster or end a
little later. We didn`t want to call for too tight of a window.

In all likelihood, the valley locations probably have more like
a 3-6hr time period when ice may accrete before the temps warm
enough to make it plain rain. But, the hills/ridgetops can stay
sub-freezing longer into many events. For example, the 00Z NAM
and GFS BUFKIT soundings both turn the precip type at UNV
(1150ft MSL elevation) to plain rain at 17Z. At that time,
though, the temp profile has the temps at 1000ft still sub-
freezing. Our surrounding ridges are that high above the valley
floor (1900-2400ft MSL). That may be due to a boundary layer of
the cold air staying in place while the warmer air works down
from above - and the valley sfc warms due to the sun. On the
other hand, the fast (30-50KT) winds in the LLJet of the warm
advection could mix/force the warm air down onto the ridgetops
before or at the same time as the valleys gets warm. But, from
personal observation, the scenario where the ridges stay
colder-longer than the valley is just as common.

The arrival time of the precip lends itself to keeping the
temps colder-longer. As for the NW: The northwestern zones may
also need an advisory eventually, but confidence is just a
little lower there for a glaze to occur. The temps may warm just
enough before precip starts to keep it all rain. Collaboration
among the WFOs resulted in holding off on issuing for them
(Warren and McKean) on this shift.

NAM hints at the llvl moisture increasing before the higher
clouds drop larger hydrometeors into it. Thus, there could be
some freezing drizzle before the main push of mix arrives. This
is another reason to start the advy a little earlier than most
of the guidance brings the measurable precip in. The criteria
for a winter weather advisory for freezing rain as the threat
is: any. Even if it just the thinnest of glazes due to the
hazard it presents to travel, even on foot.

---------------------------------------

KEY MESSAGE 2: Periods of rain with temperatures very much
above normal Wed onward

An amplifying mid/upper level ridge off the SE U.S. coast for
Wed-Fri will support a big sfc high parked off the East Coast.
These features will direct plenty of warm and moist air at the
surface and aloft north and into the state for the rest of the
week and weekend.

Temps are slated to be well above normal with sfc dewpoints
climbing in to the 40s and possibly lower 50s in some areas later
in the week. The W-E frontal boundary does become pretty
stationary around our latitude, but will be wavy. There is a
possibility of a small surge of cooler air sliding down from the
NE (backdoor cold front) Friday-ish. But, by then, the temps
will be so warm that no threat exists for any wintry precip. It
should all be plain rain. Our wavy front will be the pathway
for repeated shots of forcing and constant lift. So...it should
be a wet time. But, that`s not so bad, considering some of the
area is still in drought.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
VFR conditions will continue into the afternoon under varying
amounts of high cloud cover with a disturbance passing to our
south. A few flurries could sneak into southern PA during the
late morning/early afternoon, but they should remain south of
all TAF sites. Winds will initially be out of the northeast,
but will gradually become southeasterly for the afternoon. This
will usher in increasing low-level moisture and MVFR ceilings
should develop at JST and AOO between 20Z and 00Z. These low
clouds will spread northward across the rest of Central PA
through the evening and gradually lower through the night,
likely falling to IFR for most of the region by 12Z Tuesday.

Freezing drizzle will be possible at JST, AOO, and UNV after 03Z
as the clouds thicken ahead of a warm front lifting northward
into the region. Steady precipitation will enter from the
southwest and will expand to the north and east through the
night, likely reaching all TAF sites by sunrise. Most of this
will fall as freezing rain, though some snow or sleet may
initially mix in to the east of UNV.

There is low potential for LLWS to develop at the western TAF
sites towards the end of the 12Z period as southwesterly winds
at 2000 feet increase to around 40 knots, but we will keep it
out of the TAFs for now as it appears to fall just short of
criteria for now.

Outlook...

Tue...Restrictions likely in a light wintry mix which will
change to rain Tuesday afternoon. LLWS likely by the afternoon.

Wed-Fri...Restrictions possible in periods of rain.

&&

.CLIMATE...
It was a very dry meteorological winter (Dec-Jan-Feb).
Some of our long-term climate stations cracked the top-ten of
their driest winter seasons (Dec 1st-Feb 28/29th).

Station Total Precip Rank Period of
(inches) (Driest) Record (since)
------------ ------------ -------- --------------
Altoona 4.15 5th 1948
Bradford 4.25 2nd 1957
Harrisburg 6.05 17th 1888
Johnstown 4.93 3rd 1892
Williamsport 5.24 15th 1895

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 AM to 4 PM EST Tuesday for
PAZ006-037-041-042.
Winter Weather Advisory from 7 AM to 1 PM EST Tuesday for
PAZ010>012-045-046-049>053-058.
Winter Weather Advisory from 4 AM to 1 PM EST Tuesday for
PAZ017>019-025>028-056-057-059-063-065-066.
Winter Weather Advisory from 1 AM to 1 PM EST Tuesday for
PAZ024-033>036-064.

&&

$$

WHAT HAS CHANGED...Dangelo
KEY MESSAGES...Dangelo
DISCUSSION...Dangelo
AVIATION...Bauco
CLIMATE...Dangelo

Forecaster's
Discussion: