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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 220143
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
943 PM EDT Sun Apr 21 2024

.SYNOPSIS...
Frost/Freeze headlines are in effect early Monday morning for
the potential for sub-freezing temperatures. The next chance of
precipitation will be Tuesday night into Wednesday with a
passing cold front.

&&

.NEAR TERM /UNTIL 1 AM MONDAY MORNING/...
-- Changed Discussion --
KEY MESSAGES:

- Below average temperatures and a clear sky continues for the
  next 3 hours.

- No Hazardous weather.

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

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

Clouds have dissipated late this evening. Radiational cooling
will prompt temperatures to take a dive into the mid-30s between
now and 1am, enhancing frost formation to start across the
region.

Temperatures will continue to trend below average under cold,
northwest flow as a trough lifts to our north.
-- End Changed Discussion --

&&

.SHORT TERM /1 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Frost/Freeze headlines are in effect across the region between
  1am to 9am; sensitive plants will likely experience damage if
  not protected.
- Below average high temperatures will continue Monday afternoon
  as cold air lingers across the region.
- Frost/Freeze potential will remain low Monday night into
  early Tuesday with warm, moist advection.
----------------------------------------------------------------

A Frost Advisory and Freeze Warning are in effect from 1am to
9am Monday due to lingering cold air from an exiting trough to
the north, clearing sky, and light winds. Probability of <=32F
is above 80% for areas north of Pittsburgh and within the
ridges; hence the Freeze Warning. Elsewhere, a Frost Advisory
has been issued for temperatures ranging between 35F to 32F.

Temperatures will recover to near 60F during the day with
building high pressure and abundant sunshine, but will still be
several degrees below normal.

With warm, moist advection late Monday night, the probability
of frost/freeze products being issued is low. Temperatures will
actually be near the climatological norm across the region into
early Tuesday morning with cloud coverage building.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
KEY MESSAGES:

- The potential for Frost/Freeze headlines remains low through
  Wednesday.
- 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.
- There is a potential for strong thunderstorms Sunday into
  Monday.
-------------------------------------------------------------------

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. Prior to the onset of
measurable precipitation, expect gusty conditions with diurnal
mixing of linger dry air and 850mb winds ranging from 25kt to
35kts from the southwest.

The axis of heavier rainfall is expected to be in the vicinity
of I-80 with the passing cold front, associated with the lag in
the progression of the trough over the Great Lakes. For
rainfall amounts through Wednesday, the latest run of the NBM
suggest areas south of Pittsburgh could range from 0.20 inches
to 0.40 inches; areas near I-80 could range from 0.45 to 0.75
inches. Along with rain, shallow instability (35J/kg to 150J/kg)
may prompt some thunderstorms along the cold front between 4am
to 11am Wednesday morning.

With clearing clouds late Wednesday and cold advection, the
potential for frost/freeze conditions increases again early
Thursday morning. At the moment, confidence is medium that
Freeze Warning will be needed north of Pittsburgh and within the
ridges. However, the Warning may need to be issued as far south
as I-70 if the upper-lvl trough dives farther south.

Cold air will likely exit the region Friday as a ridge axis
builds over the Great Lakes in response to a developing low
pressure system off the Rockies.

Shower and thunderstorms chances increase late Friday as this
noted disturbance advances into the northern Great Lakes.
Organized convection, at the moment, appear promising in areas
to our west (Indiana/western Ohio) than over our region due to
weak destabilization. However, if high pressure weakens over
the East Coast, allowing the advancement of low-lvl moisture
under strong bulk shear, there`s a chance of severe storms
Sunday and/or Monday.
-- End Changed Discussion --

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Increasing dry air advection and subsidence under building high
pressure has begun to erode the diurnally driven cellular
cumulus and will give way to clear skies overnight with wind
becoming generally 5 knots or less and backing more
southwesterly as mixing ceases.

More VFR cumulus are expected to pop up by midday with a 70-80%
chance of bases remaining >5kft, and a bit less moisture should
support a FEW/SCT deck. Despite another deep mixed layer
depicted by hi res soundings up to 750 mb, not much boundary
layer wind will be available to tap into, so should be looking
at 10 knots or less through the day with high confidence. High
clouds will increase at the end of the TAF period ahead of an
approaching upper wave.

.Outlook...
The approach and passage of a low pressure system late Tuesday
into Wednesday will be the next period with restriction
potential along with widespread rain. There is high confidence
in high pressure supporting VFR conditions to end the work week.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory from 1 AM to 9 AM EDT Monday for PAZ020-021-029-
     031-073-075.
     Freeze Warning from 1 AM to 9 AM EDT Monday for PAZ007>009-
     013>016-022-074-076>078.
OH...Frost Advisory from 1 AM to 9 AM EDT Monday for OHZ039>041-
     048>050-057>059-068-069.
WV...Frost Advisory from 1 AM to 9 AM EDT Monday for WVZ001>004-012-
     021-509.
     Freeze Warning from 1 AM to 9 AM EDT Monday for WVZ510>512.

&&

$$

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