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000
FXUS61 KPBZ 191445
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1045 AM EDT Fri Apr 19 2024

.SYNOPSIS...
Warm start to the day with showers and a rumble of thunder as a
cold front crosses. Saturday and Sunday are dry but cool under
high pressure with the potential for frost/freeze impacts,
especially as we go into Sunday and Monday morning. A warmup
back to seasonal values is in store next week. The warmest day
of the next seven appears to be Tuesday at this point.

&&

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

-  Showers with isolated thunder will cross the region through
   the early afternoon.
-  Hazardous weather is not expected.

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

1030AM Update...

Updated temperatures based on quick warm up noted with the
departure of the first round of showers before the wind shift.
Some peeks of sun through the cloud cover will help increase
heating as well and tried to best represent this quick warmup
through the noon hour before temperatures start to fall with the
cold front. Latest mesoanalysis does suggest some meager CAPE in
NW PA so will maintain thunder wording for second round of
shower this afternoon.

620AM UPDATE..

Minor changes made to hourly temperatures and PoPs based on
latest observational trends. AMDAR soundings show a significant
amount of dry air from 700mb down, so current shower activity
crossing the region should not result to much in the way of QPF,
but a subtle cool down in temps and some momentary breezes as
they cross. Although there is a non-zero probability of a few
rumbles of thunder this morning, have removed thunderstorm
mention from the forecast for the morning based on latest
mesoanalysis. Previous discussion follows.


PREVIOUS..

Showers with isolated thunderstorms will traverse the region
through the early afternoon in association with a fast-moving
shortwave exiting the base of the Central Plains trough.
Precipitation will first cross ahead of a pre-frontal trough
this morning, becoming less organized as it hits the drier
airmass in place while seeing jet-aided ascent lift northward.
The second round will be redevelopment during the afternoon
along the surface cold front as it enters western PA and the
higher terrain. Little to no instability and weaker forcing will
keep hazardous weather at a minima with total accumulations less
than 0.5" (~80% probability of not exceeding that amount).

Temperature will fall toward seasonal average amid cold, dry
advection behind the front and falling heights aloft as the
upper trough axis approaches from the west. Dry conditions will
develop shortly after the cold front, with the overnight period
featuring dwindling cloud cover.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
KEY MESSAGES:

- Slightly below average temperature and dry weather expected
  through the weekend.
- Potential for frost and/or freeze impacts each of Saturday and
  Sunday mornings.
----------------------------------------------------------------

The Upper Ohio River Valley will be positioned underneath upper
troughing Saturday, including passage of the trough axis during
the afternoon hours. Its passage will push a reinforcing shot of
cooler air into the region, ensuring area temperature falls a
few degrees short of the daily average. Current coarser
resolution models suggest minimal column moisture leading to a
lack of precipitation chances with the frontal passage; however,
hints from convective allowing models portray at least low-
probability showers developing within the cold advection, NW
flow wake (likely little to no QPF). Quasi-zonal flow will
develop Saturday night into Sunday, maintaining dry conditions
under the influence of surface high pressure and favoring
slightly below average temperature.

The key component for this period will be frost/freeze risk as
the forecast area is well-within it growing period (save for
Tucker County). Latest solutions suggest a more muted frost
threat Saturday night due to slightly elevated winds disrupting
frost formation; however, freeze remains a threat as portions of
northwest PA exhibit a 40-70% chance for see temperature at or
below freezing (though likely only for an hour or two near
dawn). For Sunday night, the clearer skies and lighter winds
of Sunday night better aligns with widespread frost potential;
some height rises will temperature freeze potential (20-40%).

&&

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


- The next low pressure system and associated precipitation
  chances is likely for late Tuesday into Wednesday.
- Ridging is favored for the late week period, pointing to
  rising temperature heading into the weekend.
-------------------------------------------------------------------

Though ensemble models vary in trough analysis moving across the
southeast U.S. Monday, the outcome remains the same for the
Upper Ohio River Valley: rising heights aloft and the influence
of high pressure will support dry conditions and seasonable
temperature Monday.

There is fairly high consensus on the next upper level trough
and associated surface low to drop from the north central plains
through the Great Lakes late Tuesday into Wednesday. Ahead of
the system, weak warm advection will support above normal
temperature and increasing cloud cover before the systems
arrival. Widespread showers and low probability thunderstorms
are then likely as the system crosses the region. Depth of the
upper trough remains the biggest uncertainty during this period,
which will strongly influence the timing of precipitation
passage and degree of cold advection behind the system.

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 temperature
recovery in the post-cold front passage environment.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Medium to high confidence forecast /70% going to 90% after 4Z/.

VFR showers initially will yield to MVFR cigs as a cold front
moves through the region. CIGS upstream in Ohio reside between
1500 to 1800 feet. This will move through during the late
morning into afternoon hours. In wake of the MVFR conditions,
look for VFR to return from west to east after 21Z. VFR is
forecast to reach the mountains by 6Z. Once the stratocu clears,
look for VFR the balance of the forecast with just cirrus.

Wind will be an impact this morning with speeds above 12kts and
gusting between 20-25kts through the midday hours. Speeds and
gusts subside by 18Z and remain from the west - northwest
through the overnight hours.

Where the TAFs could go wrong? There could be /30% chance/ of
IFR cigs at FKL and DUJ briefly as the front moves through
perhaps even BVI and HLG as well.

.Outlook...
A ridge of high pressure at the surface will maintain VFR
conditions into next week. Showers and potential restrictions
return late Tuesday with an approaching cold front.

&&

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

&&

$$

SYNOPSIS...34/Frazier
NEAR TERM...34
SHORT TERM...Frazier
LONG TERM...Frazier
AVIATION...McMullen