-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 202349
AFDPBZ

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

.SYNOPSIS...
Dry, cool, and breezy conditions are expected through the late
evening. Frost Advisory/Freeze Warning issued across the region
for the potential of sub-freezing temperatures. Building high
pressure will return above average temperatures mid-week.

&&

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

-  Breezy conditions will continue for the lower elevations
   through 6pm; higher terrain through midnight.
-  No Hazardous weather.

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

Sub-advisory wind gusts have been measured at ASOS/AWS stations
early this afternoon. Max wind gusts have ranged from 40mph to
44mph due to tight pressure gradient associated with a passing
shortwave trough. Probability of 46mph gusts (Wind Advisory
criteria) remains low across the region, even in eastern Tucker
County (probability is less than 25% within the ridges).

Hi-Res guidance indicates that the probability of 35mph gusts
will remain elevated through 6pm for lower elevations; higher
terrain through midnight as the pressure gradient gradually
reduces in intensity. Otherwise, dry and quiet weather will
continue today.

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 /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.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