PBZ issues Area Forecast Discussion (AFD) at Nov 14, 11:50 AM EST597
FXUS61 KPBZ 141650
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1150 AM EST Thu Nov 14 2024
.SYNOPSIS...
Rain chances remain elevated throughout the day with a passing
low pressure system. Near to slightly above average temperatures
are expected Friday and Saturday under northwest flow.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Rain crosses the area today, diminishing overnight.
- Precip amounts for the next 24 hours: Probability of 0.25 inch
is elevated (above 70%) across the region; 0.50 inches between
70% and 100% south of I-70.
------------------------------------------------------------------
Swath of rain continues to slowly shift northeastward across the
area as low pressure crosses the Great Lakes. There remains a
sharp cutoff in rainfall northeast of Pittsburgh with low-level
dry air in southeasterly flow. To the west, a break in more-
widespread rainfall is already occuring near Zanesville and will
continue to slowly shift northeast through the afternoon as
scattered, light showers linger. Totals across eastern Ohio have
been between 0.25" and 0.75" so far.
A Special Weather Statement continues through 17z for eastern
Tucker County, WV, where initial wetbulbing with showers allowed
temperatures to hover near freezing. Any lingering cold spots
should warm back above-freezing by noon. Overcast conditions
with rain will keep high temperatures below 50F for most of the
area this afternoon.
Lingering rain showers will diminish overnight as the mid-
level low shifts overhead and eventually southeast of the area
by Friday morning.
&&
.SHORT TERM /FRIDAY/...
KEY MESSAGES:
- Drying trend begins Friday and lasts into this weekend.
-------------------------------------------------------------------
500mb height rises are expected Friday in the wake of
Thursday's low with drier weather expected as surface high
pressure builds across the Great Lakes and Ohio River valley
into Friday night. Temperatures Friday afternoon will recover to
slightly above normal for mid-November with highs mainly in the
50s. However, with northwest flow aloft and lingering low-level
moisture, could see a few lake showers remain across western PA
Friday night before drier air arrives. Little accumulation is
expected, with latest NBM probability of exceeding a tenth of
accumulation remaining around or slightly above 5 percent.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:
- Highs a few degrees above normal for the weekend.
-------------------------------------------------------------------
A high amplitude pattern is shown to continue over the weekend
into early next week. Ensemble cluster analysis indicates that
the primary issue will be timing of the upper ridge spreading
east into Great Lakes and Ohio Valley Saturday due to a low
moving and deep low near Nova Scotia. Readings may well be near
normal on Saturday if the trough hangs on a bit longer to the
east.
Most of the ensemble guidance has the upper ridge overhead by
Sunday, suggesting highs about 5F above normal. Primary
uncertainty is related to the details of a trough lifting
northeast out of the northern Plains towards the Great Lakes,
and a potential short wave trough digging into base of western
Atlantic trough near New England. Neither of these features
would impact our area much other then minor differences in
temperatures.
Uncertainty begins to increase significantly by Monday and
Tuesday. While many of the global ensemble members keep a
somewhat flattened ridge overhead with mild weather continuing,
a significant number of ECMWFE members dig the Great Lakes
trough southeast and lower the heights across area. The NBM 10th
to 90th percentiles show this range of possibilities well,
ranging from middle 60s/10F above normal with the ridge
remaining in place, and near normal and lower 50s if the trough
digs southeast per subset of ECMWFE members.
Potential exits for a short wave trough to eject out of the
central US long wave trough position on Monday and potentially
be in the Middle Mississippi River Valley. Ensembles have
tendency to build the ridge downstream of this feature into the
Great Lakes and Ohio River Valley, which would keep readings
above normal (per the NBM 90th percentile MaxT in the mid to upper
60s Monday and Tuesday). While the ejecting and weakening trough
could bring showers around Tuesday to the area, it appears that
significant rain chances will be slow to move east from the
central US as the ensembles hint at a blocking pattern with long
wave trough remaining anchored somewhere near NM to TX area.
&&
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Rain (moderate at times) will continue to overspread the region
ahead of a warm front this morning. MVFR visibilities and
ceilings are already being reported at ZZV, with IFR conditions
noted in obs just upstream across central OH. Between 14z-19z,
expect these MVFR/IFR ceilings to fill in areawide amid top-
down moistening, with probabilities favoring greater reductions
at ZZV/FKL/DUJ/BVI. The influx of dry air in near-surface
downslope (southeast) flow should delay cig restrictions at
terminals along and west of the Laurel Highlands and adjacent
ridges of northeast WV (namely PIT/AGC/LBE/MGW), though these
terminals too should eventually drop to MVFR by afternoon.
Surface winds will remain ESE through 00z and occasionally
gusty to 20-25kts.
As the upper trough shifts southeast of the region after 00z,
rainfall will gradually end with only pockets of light rain or
drizzle remaining and surface winds becoming light/variable.
Settling of boundary layer moisture and the onset of cold
advection should aid higher confidence in widespread MVFR and
localized IFR ceilings after 06z (50-90% probabilities).
Outlook...
Passage of the cold front initiating cold advection and NW flow
are factors that are likely to maintain MVFR conditions with low
probability rain chances through the day Friday, favoring
eastern OH and northwest PA.
VFR is more likely to return Saturday under greater influence of
high pressure with stronger subsidence as ridging develops
aloft. The next potential shortwave disturbance could cross
Monday and offer increased rain/MVFR cig chances.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Rackley
NEAR TERM...Hefferan/Rackley
SHORT TERM...88
LONG TERM...Craven/Shallenberger/88
AVIATION...Cermak/Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Nov 14, 11:50 AM EST---------------
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