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000
FXUS61 KPBZ 210115
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
915 PM EDT Sat Apr 20 2024

.SYNOPSIS...
Frost Advisory/Freeze Warning in effect early Sunday morning.
The potential for frost continues early Monday morninging with
linger cool air. Building high pressure will return above
average temperatures mid-week.

&&

.NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
KEY MESSAGES:

-  Breezy conditions may linger in the higher terrain through
   midnight.

-  No Hazardous weather.

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

9pm Update: No major changes have been made to this forecast
period.

Previous Discussion: Dry and quiet weather will continue
through midnight. Wind gusts, 25mph to 35mph, may continue in
the ridges due to mountain wave activity. Otherwise, wind gusts
have subsided across the region due to decoupling and exiting
shortwave trough.

Temperatures will continue to trend below average by 5 to 10
degrees with cold advection under northwest flow.

&&

.SHORT TERM /MIDNIGHT TONIGHT THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Frost/Freeze impacts are expected tomorrow morning; Freeze
  Warning/Frost Advisory issued from 2am to 8am.
- Frost/Freeze impacts are expected again early Monday morning.
- Below average temperature and dry weather is expected to
  continue through Monday afternoon.
----------------------------------------------------------------

High pressure will continue to build in from the west,
maintaining dry conditions through the weekend.

As for the Freeze Watch, areas near I-80 and the ridges of PA
have been upgraded to a Freeze Warning. Hi-Res ensemble
guidance continues to have high probabilities (above 70%) for
temperatures <=32F early Sunday morning for counties north of
Pittsburgh and within the ridges of Pennsylvania.

Confidence is considered low for a Freeze Warning in areas
south of Pittsburgh due to lingering winds and/or increase cloud
coverage limiting radiational cooling. Therefore, a Frost
Advisory was issued instead with temperatures ranging in the
mid-30s to just above freezing.

Below average temperatures and dry conditions will continue
Monday. Frost/Freeze products will once again need to be
coordinated with neighboring offices for late Sunday/early
Monday. At the moment, the NBM is leaning towards only a few
counties (Forest/Clarion/Jefferson) that might need a Freeze
Warning. However, the probability of <=32F is only 50% due to
exiting cooler air aloft as a ridge builds to the west and Frost
Advisory may be better suited.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
KEY MESSAGES:

- The potential for Frost/Freeze headlines decreases through
  Wednesday under warm, moist advection.
- The next low pressure system and associated precipitation
  chances is likely for late Tuesday into Wednesday.
- Frost/Freeze potential returns Wednesday into Thursday with a
  passing trough over the Great Lakes.
-------------------------------------------------------------------

A flux in low-lvl moisture and southwest flow under a ridge will
decrease the potential of frost/freeze headlines through at
least Wednesday.

Near to above average temperatures are anticipated Tuesday
afternoon ahead of an approaching cold front and its associated
trough. Probability of measured precipitation increases from
west to east after 18Z Tuesday. The axis of heavier rainfall is
expected to be north of Pittsburgh, associated with stronger
forcing and perhaps lake enhancement on the backside of the
front. For rainfall amounts through Wednesday, the latest run of
the NBM suggest areas south of Pittsburgh could range from 0.15
inches to 0.40 inches; areas near I-80 could range from 0.25 to
0.60 inches. Along with rain, shallow instability (15J/kg to
50J/kg) may prompt some thunderstorms along the cold front.

With clearing clouds late Wednesday and cold advection, the
potential for frost/freeze conditions across the region
increases again early Thursday morning.

The late week period will be defined by the progression of the
upper trough through the northeast CONUS and the rapidity of
height rises in its wake. Dry weather will be favored given
high confidence of surface high pressure, with the degree of
temperature recovery in the post-cold front passage environment
dictated by said height rises.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Diurnally driven cumulus/stratocumulus have begun to dissipate
with loss of daytime heating and will continue to do so after
sunset. With a pressure gradient still in place, hi res ensemble
guidance favors wind remaining elevated for a couple hours
after sunset even with the loss of deep mixing until the
gradient lessens, most likely after 04z.

Cirrus coverage will increase overnight in westerly flow aloft.
These clouds may thicken a bit while wind goes largely light
and variable as surface ridging builds. Mid-level moisture will
then increase some as well ahead of an approaching shortwave in
the latter half of the overnight hours, most likely ensemble
timing after 10z, with the probability for CIGs lower than 6kft
less than 40%. Said shortwave axis will pass through Sunday
afternoon and reinforce low to mid level cloud coverage with the
old Cu rule favoring a SCT deck but surface high pressure will
keep the area dry with a only a 30-40% chance of CIGs dipping
below 5kft (higher chances for KFKL/KDUJ) and high confidence
VFR remains.

With a weaker pressure gradient Sunday, wind will not be nearly
as gusty, with peak values likely around 10 knots out of the
northwest.

.Outlook...
High confidence in VFR conditions through a majority of Tuesday
under the influence of high pressure. Passage of a low pressure
system will bring widespread precipitation and restriction late
Tuesday into Wednesday. Ensemble models favor dry weather and
VFR conditions to end the work week.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 2 AM to 8 AM EDT Sunday for PAZ020-021-029-
     031-073-075.
     Freeze Warning from 2 AM to 8 AM EDT Sunday for PAZ007>009-
     013>016-022-074-076>078.
OH...Frost Advisory from 2 AM to 8 AM EDT Sunday for OHZ039>041-
     048>050-057>059-068-069.
WV...Frost Advisory from 2 AM to 8 AM EDT Sunday for WVZ001>004-012-
     021-509>513.

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan/Frazier
AVIATION...MLB/CL