PBZ issues Area Forecast Discussion (AFD) at Oct 27, 7:27 PM EDT970
FXUS61 KPBZ 272327
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
727 PM EDT Sun Oct 27 2024
.SYNOPSIS...
High pressure maintains dry weather and increasing temperatures
through mid-week. A cold front passes on Thursday bringing rain
chances to the area and a cooler airmass for the end of the
week.
&&
.NEAR TERM /THROUGH MONDAY/...
KEY MESSAGES:
- Lows below normal.
-------------------------------------------------------------------
No major changes for the evening update. Very low dewpoints have
mixed down to the surface during the afternoon, so have lowered
dewpoints through the evening. Clouds were also updated to
account for the area of mid-high clouds moving southeastward in
the northwest flow aloft.
Previous discussion...
With the center of the high still overhead tonight, light wind,
clear skies, and low dew points, have again undercut NBM for lows
with ideal radiational cooling conditions; this points toward values
5-10 degrees below normal. Some patchy river valley fog is again
possible.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
KEY MESSAGES:
- Dry with gradually increasing temperatures.
-------------------------------------------------------------------
As the high migrates ever so slightly off to the east on Monday,
return flow will begin as warm advection aloft cranks 850 mb
temperatures to 6-9C as heights rise. The 850 mb rule suggests high
temperatures in the mid to upper 60s from Pittsburgh south supported
by the NBM's 70-95% chance of >65. With some weak moisture
advection, will not see dew points mix out in the afternoon as they
did the previous couple days. This will also work in tandem to hold
overnight lows Monday night nearly the opposite of Sunday night at 5-
10 degrees above average.
A warm front will lift by to our north accompanied by a weak
shortwave traversing the axis of the ridge late Tuesday morning.
Weak forcing and displacement of the best moisture to the north
should preclude more than an increase in cloud coverage, though
won't entirely rule out a shower in and around the I-80
corridor. How far north and how quickly morning cloud coverage
retreats will determine high temperatures. Confidence is highest
for more sun further south where the lower end of the ensemble
distribution suggests the highest potential for clearing.
Tuesday will feature the most significant height rises (4-5 dam
in 12 hours) and strong warm advection will push highs into the
70s for most, save our far northeast zones.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
KEY MESSAGES:
- High confidence dry weather and above average temperatures
through Wednesday.
- Next chance for rain comes Thursday with a cold front.
- Cooler airmass settles in on Friday.
-------------------------------------------------------------------
Ensembles migrate the high east out off of the coast of New England
come Wednesday with upper ridging still in place which should foster
the strongest return flow on its backside. Some subtle differences
show as the ensembles try to capture the evolution of the ridge
downstream of an approaching shortwave across the Upper Plains, but
even a scenario with a faster trough/more quickly shunted ridge
keeps the most uncertainty out of our area lending high confidence
(60-80% chance) of 850 temps >12C and heights approaching 590
dam. Probability of 75 degrees sneaks up to 60-90% Wednesday,
but an increase in column moisture isn't going to allow for full
sun; if we have any shot of approaching 80F, it's most likely
south of Pittsburgh and contingent on more clearing of clouds
than the ensembles' mean. More uncertainty then arises on
Thursday as a cold front approaches. Highs have a chance at
being similar to those of Thursday, but contingent on FROPA
timing. 3/4 ensemble clusters introduce rain chances in the
afternoon hours which would cap high temps while the other
solution with a flatter, northward displaced shortwave holds it
off until later in the evening and may help keep trick or
treaters drier.
Rainfall amounts with this system are still lower confidence, but
the good news is that the probability for a wetting rain (0.10") is
80-95%. A tail in the QPF distribution up to ~0.75" contingent on
capitalization of marginal instability and slightly higher PWAT
values is possible but low confidence. Behind the front, upper
troughing will depart as high pressure builds. Drier, cooler air
settles in on Friday with moderation to temperatures by next weekend.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
High confidence in VFR with light winds and occasional passing
cirrus through the TAF period under the influence of high
pressure.
Patchy river valley fog may develop between 06z-12z Monday due
to strong radiational cooling. However, the probability of
terminal impact (mainly FKL/HLG) remains too low for mention.
.Outlook...
VFR continues through Wednesday as high pressure positions east
of the region and winds slowly increase/veer out of the south.
An upper level shortwave trough and surface cold front will
approach the region Thursday afternoon into Friday morning,
bringing with it increased rain chances and potentially
MVFR/IFR restriction development.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...MLB
NEAR TERM...22/MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Cermak
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 27, 7:27 PM EDT---------------
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