PBZ issues Area Forecast Discussion (AFD) at Oct 20, 7:20 PM EDT494
FXUS61 KPBZ 202320
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
720 PM EDT Sun Oct 20 2024
.SYNOPSIS...
High pressure will maintain dry and warm weather Wednesday.
Rain chances return late Wednesday and Thursday with a crossing
cold front.
&&
.NEAR TERM /THROUGH MONDAY/...
KEY MESSAGES:
- Dry weather and clear skies continue
-------------------------------------------------------------------
6pm update...
Attempted to capture temperature trends from peak heating to
overnight cooling based on previous days readings; this setup
has tended to favor near 90th percentile temps over the next few
hours for elevated locations while closer to 50th or lower
percentiles in valleys reflecting the stronger, quicker
radiational cooling to occur within valleys. These trend should
hold through 9-10pm readings before hourly temperatures more
approximate model mean values.
Regardless, this does little to change the overall messaging
for the evening.
Rest of the Discussion....
High pressure will remain centered across the Ohio
Valley region tonight, maintaining clear skies and dry weather.
The atmosphere will decouple again tonight, though wind above
the boundary layer will be slightly higher than recent nights.
This should result in low temperatures a few degrees warmer than
recent nights for most areas.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:
- Dry weather through most of Wednesday
- Warming trend continues through Tuesday
- Shower chances return by Wednesday night
-------------------------------------------------------------------
High pressure will remain centered across the Ohio Valley
region through early Tuesday. The high will then slide east by
Tuesday afternoon. Warm 850mb temperatures from 12 to 14 deg C,
and 500 mb heights ranging from 584 to 588 dm, will result in
high temperatures from 15 to 20 degrees above average through
Tuesday. Nudged temperatures toward the high end of guidance
during the day, and the low end at night, with large diurnal
swings expected with dry air in place.
A weakening shortwave trough will advance eastward out of the
Midwest Tuesday night, crossing the Upper Ohio Valley region
early Wednesday. Little moisture is expected to be associated
with this weakening trough, with the main impact on the forecast
being slightly cooler high temperatures.
A second, stronger shortwave and its associated surface cold
front, will approach and cross the region late Wednesday and
Wednesday night. While moisture and lift will be more favorable
for a few showers with the second shortwave, both are still less
than optimal for anything more than minimal rainfall amounts and
scattered precip coverage.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
KEY MESSAGES:
- Near normal to slightly below average temperatures return
Thursday in the wake of a cold front; light precipitation
chances north of Pittsburgh
- Large variability in the pattern over the weekend
-------------------------------------------------------------------
By early Thursday morning the cold front and associated upper-
level trough is expected to near or in the vicinity of the
region. Over the last 24 hours, the NBM has backed off on
precipitation amounts south of Pittsburgh and generally
confided probabilities (30-40%) between Pittsburgh and Lake
Erie. Noted dry air aloft (above 800mb), advancing from the
west, will likely keep some areas dry and precipitation may depended
more-so on NW flow and lake enhancement.
Temperatures will trend near to slightly below average Thursday as
a ridge from the west tries to advance quickly behind the
front. Breezy conditions may be noted in the wake of the front
along the ridges Thursday afternoon.
Model ensembles depict large variability in the general synoptic
pattern Friday through Sunday. The overall strengthen of a
building trough or ridge over the Great Lakes creates a large
spread in temperatures (by about 10 degrees) within the 25th
and 75th percentile NBM; low-60s vs. low-70s on Saturday/
mid-50s vs. mid-70s Sunday. The overall strength of a ridge
over the Pacific Northwest will reflection on our trends.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
VFR is expected through the TAF period under high pressure.
Wind will be light, and mainly from the SW with the high
centered south of the area.
.Outlook...
High pressure should maintain VFR conditions and light winds
through early Wednesday. Low rain and restriction chances
return with a Wednesday night cold front. VFR expected again
Thursday under building high pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM/Frazier
SHORT TERM...WM
LONG TERM...Hefferan
AVIATION...WM/Cermak
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 20, 7:20 PM EDT---------------
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