161
FXUS61 KPBZ 072230
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
630 PM EDT Mon Apr 7 2025

.SYNOPSIS...
Rain that rapidly transitions to snow will accompany a strong
cold front this evening, with isolated lake enhanced snow
showers continuing into Tuesday morning. Impacts are expected to
be limited as accumulations mainly occur on grassy or elevated
surfaces. Another period of seasonably cool and wet weather is
expected Thursday into next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
KEY MESSAGES:

- Rain will rapidly change over to snow with cold front passage
- Though accumulations of 1 to 2 inches are possible, impacts
  will be low due to warm surfaces and roadways.
- Dry but cool weather expected Tuesday.
-------------------------------------------------------------------

The cold front is right on our northwest doorstep at this time,
in line with earlier expectations. Trended towards HRRR values
for expected wind gusts with the boundary. Steep low-level lapse
rates ahead of the front will allow for mixing/downward
momentum transport with FROPA - gusts of 30 to 40 MPH are
certainly possible.

The discussion below lays out the expected scenario well. Quick
mix with/change to snow is indeed occurring soon after frontal
passage, but with more impressive cold air (lower than -10C at
850mb) lagging the front and with moisture not penetrating the
full height of the dendritic growth zone, snow rates will be
hampered initially, and any accumulation will still be mainly
limited to grassy/elevated surfaces.

Previous discussion...

Enhanced lift along the cold front is expected to lead to a
narrow band of showers where thermal profiles quickly shift from
a rain to snow for precipitation type. Modest moisture depth
combined with delayed arrival of the colder air aloft should
ensure initial snowfall rates are lower (keeping visibility to
1 to 2 miles) and limit snow squall potential (not to mention
prior warm surfaces). Within a few hours of frontal passage, dry
advection will temper shower activity until NW flow aloft better
taps Lake Erie moisture to develop a few lake-enhanced snow
bands during the overnight hours. HREF modeling suggests a quick
1-2" of accumulation can`t be ruled out if band
duration/intensity is maximized, but warm surfaces should
ensure minimal impacts (accumulations mainly occurring on grassy
or elevated surfaces).

High pressure to the west and slowly rising heights aloft will
erode showers Tuesday and attempt to dissipate lingering
stratocu. The cold airmass in place should lead to areal
temperature that is around 20 degrees below the daily average.
As the growing season hasn`t official started, no freeze
products will be issued; that said, expect each overnight period
to feature below freezing temperature that may necessitate
protection of outdoor vegetation that is vulnerable to cold
temperature.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Well below normal lows again Wednesday morning.
- Precipitation returns later Wednesday through Thursday.
-------------------------------------------------------------------

Increasing subsidence and a shallower boundary layer will end
any precipitation on Tuesday. Broad surface high pressure
building in from the west will then maintain dry conditions
through Wednesday should keep the area dry for much of Wednesday
before rain returns ahead of an approaching low later in the
day. The mentioned low center is progged to then pass north of
the region on Thursday. Warm advection in southerly flow will
then moderate temperatures.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
KEY MESSAGES:

- Below-average temperatures expected through Saturday
- Precipitation ends later on Saturday

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

Long-range ensemble models remain consistent, showing a cool
pattern through Saturday. A large-scale trough over our region
will likely keep afternoon highs below 60 degrees, with less
than a 25% chance of exceeding that, during this time period.

The highest chance of precipitation will be Thursday afternoon
into Thursday night as a low-pressure system moves through the
Midwest and Ohio River Valley. While rainfall amounts of over a
half inch are currently unlikely (less than 20%) higher
elevations could see closer to that amount due to upslope flow.
There`s a possibility of continued precipitation Friday into
Saturday if this noted trough stalls as indicated by a few long-
range ensemble models.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Dry slotting and increasing southwest flow ahead of an incoming
trough axis will slowly erode lingering MFR/IFR east/southeast
of KPIT this afternoon. There is growing potential that sites
like LBE/MGW never lose restrictions before the expected cold
frontal passage.

The potent upper trough axis will cross the region between 22z
and 06z, pushing a strongly forced surface cold front southeast
during that time frame. Meager moisture will limit precipitation
duration but a narrow band of showers is favored along the
front; thermal profiles suggest a rapid transition (less than 1
hour) from rain to snow amid strong column cold advection.
Limited moisture in DGZ should keep snowfall rates lower, but
hi-res modeling suggests a 30-50% chance for IFR vsbys in the
snow frontal zone.

A hodgepodge of scattered/broken low VFR to high MVFR cigs is
likely in the post-frontal environment given cold/dry NW flow.
There is a signal for a few lake enhanced bands that develop aft
06z favoring northwest PA, but uncertainty in its
location/strength precluded more notable TAF mention. Be alert
that it is possible for these very narrow bands to briefly drop
vsby/cigs to IFR/MVFR levels, respectively.

Outlook...
High pressure to the west and gradually rising heights aloft
will end precipitation chances and erode VFR/MVFR stratocu by
Tuesday evening.

The next low pressure system arrive late Wednesday into Thursday
and is likely to initiate another prolonged period of
restrictions and occasional precipitation chances as deep Great
Lake troughing develops.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Frazier/CL
SHORT TERM...Hefferan/22/88
LONG TERM...Hefferan/88
AVIATION...Frazier