NWS Forecast Discussion
259
FXUS61 KCTP 281721
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
121 PM EDT Mon Apr 28 2025
.SYNOPSIS...
* Abundant sunshine, light winds, and mild temperatures this
afternoon under a ridge of high pressure.
* Warmer temperatures and moderate humidity returns for Tuesday
with numerous severe thunderstorms possible during the
afternoon and evening hours across mainly the northwest half
of the Commonwealth.
* Dry conditions prevail on Wednesday with next chances of
showers and thunderstorms Thursday afternoon through Friday
night.
&&
.NEAR TERM /THROUGH TONIGHT/...
Another day of almost cloud-free skies, but this time with light
and variable winds as a ridge of high pressure over Central and
Eastern PA slides slowly to the east this afternoon.
Model RH profiles point to sunny skies and GEFS 2m temp
anomalies of +5-8F support highs ranging from the upper 60s over
the high terrain of the Alleghenies, to the low 70s most other
locations.
Fire concerns today will be mitigated somewhat by lighter winds
today compared to yesterday along with recent rainfall and
green-up across southeastern Pennsylvania. As a result, we`ve
opted for no fire weather headlines this afternoon.
Dry conditions with clear to partly cloudy skies continue into
tonight. A freshening southerly breeze will keep temperatures
+10 to +20F warmer by daybreak Tuesday compared to this morning.
Cloud cover begins to increase early Tuesday morning ahead of
an approaching upper- level trough tracking north of the area,
but the entire region should stay rain-free into Tuesday
morning.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
An upper-level trough will push through the Great Lakes Tuesday
afternoon and bring a warm front/cold front progression through
the Commonwealth on Tuesday afternoon. This warm front is
expected to lift north of central Pennsylvania Tuesday morning,
allowing for much of the area to have some residence time in the
warm sector. This is expected to allow for warmer temperatures,
especially across western Pennsylvania where there is higher
confidence on the warm sector pushing north/east of the region.
Despite these warmer temperatures, cloud cover is expected to
limit instability across the western half of the forecast area;
however, increasingly diffluent upper level westerly flow and
ample shear/veering wind with height, beneath the right entrance
region of a mid/upper-level jet will lead to a notable
potential for severe weather with a high shear-low to moderate
CAPE environment during the afternoon and evening hours Tuesday.
Current storm mode favors multicell with some supercells likely
as hodographs take on a broad loop across the NW half of the CWA
by late Tuesday afternoon with 0-1KM EHI values from 2-3.5 M2/S2
across the Central and NW Mtns between 20Z Tue-00Z Wed. Main
threats at this time for severe weather will be damaging winds
in mini bow echoes within short line segments considering
strong, westerly 0-3 KM bulk shear of 40-45 KTS, and large hail,
especially across northwest PA. Given the potential for some
"right movers" creating significantly better storm relative
inflow and lowered pressure/LCLs beneath the strong updrafts,
there is risk for a few isolated tornadoes across the NW 1/3 or
so of Pennsylvania, especially from 22Z-00Z when LCL heights
will be lowering and storms interact with llvl outflow
boundaries from the initial convection. SPC continues the
Enhanced Risk (Level 3 out of 5), which happens about 6 times
per year on average across Pennsylvania. Have multiple ways to
receive warnings and stay weather aware Tuesday afternoon and
evening.
Storms will continue moving eastward late Tuesday
afternoon/evening; however, less instability will be in place
and shear becomes less favorable, thus severe threat becomes
more limited across the Lower Susquehanna Valley. Precipitation
exits quickly and becomes more upslope/lake- enhanced rain
showers in the wake of the cold front Tuesday night into early
Wednesday morning. Storm total rainfall amounts will be
generally less than 0.25" southeast of the I-99/I-81 corridor
and perhaps exceeding 1" in parts of northwest PA that receive
multiple rounds of storms.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The cold front becomes quasi-stationary to the south of the
MD Line early Wednesday night then pivots northward as a warm
front across western PA on Thursday as a sfc low tracks from
near Chicago into Lower MI by 02/00Z. Expect shower activity to
ramp up particularly in the western/northwestern portions of
the CWA through Thursday night near the intersection of the
advancing warm front and increasing moisture transport and
theta-e advection via relatively strong SSW 850mb LLJ and IVT.
Thursday night looks very mild in CPA for the first night of May
2025 with min temps 55-65F or +15 to +25 degrees above climo.
Scattered convection is likely to accompany the trailing cold
front on Friday, followed by another potential round of showers
Friday night into Saturday associated with the parent 500mb
trough/cool temps aloft rotating through the region. There is a
broad model consensus in a cooling trend Friday night into the
first weekend of May with 24hr min/maxT deltas running 5 to 10
degrees lower vs. the previous night/day. That said, frost risk
appears to be confined to the northern tier AM Sunday where the
growing season is not active.
High confidence in a much nicer end to the first weekend of May
as high pressure builds over the area into early next week.
Expect milder temperatures and pleasant, rain-free conditions
Sunday and Monday with highs moderating into the 65-75F range.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Primary change with this TAF update has been to include several
hours of marginal LLWS late tonight and early Tuesday at all
airfields as the southerly flow (above a mainly decoupled near
surface layer) freshens to 25 to 30 kts in a layer between about
12-20 kft AGL.
High pressure across the region will (100% confidence) provide
light and variable winds and clear skies through 29/12Z. Winds
will be light and variable throughout the entire TAF period,
potentially taking on more of a southerly component by the
afternoon. High-level clouds will begin to move into western
Pennsylvania ahead of showers/thunderstorms Tuesday afternoon;
however, ceilings will remain above 25,000ft AGL.
Tue...PM showers and possibly a few thunderstorms with
restrictions possible. Brief gusty winds across W PA.
Wed...A few lingering showers across primarily SW PA.
Thu...Showers/t-storms return areawide, restrictions possible.
Fri...Showers with restrictions possible.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert/Banghoff
NEAR TERM...Lambert/Fitzgerald/Banghoff
SHORT TERM...Lambert/Banghoff
LONG TERM...Steinbugl
AVIATION...Lambert/NPB
NWS CTP Office Area Forecast Discussion
