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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 191846
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
246 PM EDT Fri Apr 19 2024

.SYNOPSIS...
-- Changed Discussion --
Cold front will continue to shift eastward through the
afternoon. A return to seasonably cool temperatures and dry
conditions is expected for the weekend. Radiational cooling will
bring 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.
-- End Changed Discussion --

&&

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

-  Cold front is continuing to progress across the region with
   very minimal precipitation.
-  Hazardous weather is not expected.

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

Cold front is reaching the ridges this afternoon, with some rain
showers starting to blossom along it. ACARS soundings and
mesoanalysis suggest about 100j/kg of CAPE, with some modest
heating ahead of the boundary which could lead to a few isolated
storms. Behind the front, temperatures are already cooling back
into the 50`s and this should be the trend as the front exits
this evening.

NBM maintains lingering cloud cover and elevated winds
overnight, though temperatures will fall back to seasonal values
under cold advection.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
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. While the passage will reinforce the cold
advection across the region, maintaining temperatures slightly
below average, there will be a lack of deep moisture or synoptic
lift to generate showers, save for closer to the lake shore and
into NY state. Deep mixing with surface heating will keep
conditions gusty on Saturday. NBM probabilities of wind gusts
exceeding 20mph are near 100% with a period of gusts exceeding
30mph along the timeframe of the trough passage.

Fairly fast, zonal flow will be present thereafter and through
the weekend with high pressure building over the region at the
surface keeping conditions dry and cool.

With ridging in place, there remains a concern for frost/freeze
as much of the forecast area is now in the growing season both
Sunday Morning and Monday Morning. The latest NBM has a 40-60%
chance both days, especially north of Pittsburgh. There is a
concern that elevated winds could be a limiting factor Saturday
night but the high pressure will be more settled over the region
Sunday night. For now, will continue to highlighted this in the
HWO.
-- End Changed Discussion --


&&

.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 /18Z FRIDAY THROUGH WEDNESDAY/...
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High confidence forecast /80%/ going to 90% after 4Z.

MVFR to VFR clouds are encompassing all the airports and this
will be the trend until 22-02Z as they exit from west to east.
Once VFR conditions arrive they will be present for the balance
of the forecast. There is a low chance of high end MVFR CIGS
after 15Z Saturday at FKL and DUJ, but for now kept them sct
given a larger consensus of the guidance.

The main impact and story will be the wind. Speeds and gusts
will subside this afternoon as the front gets farther to our
east. Wind will pick back up again late in the TAF forecast
/after 14Z Saturday/ with gusts nearing 30kts at some airports
by midday Saturday while sustain speeds are above 12kts. NBM
probabilities of wind speed greater than 15 mph is above 90%,
while prob greater than 20mph reside less than 20% and mainly
in the higher terrain. Thus confidence is higher in the 12kt
threshold being eclipsed than 20kts at this juncture.

Where the TAFs could go wrong? There could be /20% chance/ of
MVFR cigs lasting 1-3 hours longer at all airports this evening.

.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.
-- End Changed Discussion --

&&

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

&&

$$

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