Bethel Park, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

398
FXUS61 KPBZ 130507
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1207 AM EST Wed Nov 13 2024

.SYNOPSIS...
Large polar high pressure will push across Quebec tonight bringing a
clear and seasonably cold night to the Upper Ohio River Valley. Low
pressure over the northern Plains will push into the middle
Mississippi Valley late Wednesday and the Ohio River Valley
Thursday, bringing another period of rain to the region.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:

- Clear and cold tonight.
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Forecast remains on track. Dew points are currently lower than
the prior forecast package. The new update tracks this change
and nudged temperatures down accordingly tonight with greater
potential to cool. Low temperatures tonight may vary a good bit
with terrain, but lows in the mid 20s to low 30s are still a
good bet for most.

.. Previous Discussion..

Winds should drop off quickly around sunset and wind sheltered
spots should crater pretty fast. Good shot at 20s in most
locations, with lower 30s in the Pittsburgh urban heat island.
Lower 20s and perhaps even some upper teens may be seen in the
northern third of forecast area.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
KEY MESSAGES:

- Dry and seasonable Wednesday.
- Rain likely Thursday, potentially lingering through Friday.
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Sharp upper ridge moves overhead Wednesday with a dry airmass.
Despite a cold start temperatures should climb into the 50s with a
decent amount of morning sun before the high clouds start to spread
in late in the day.

Surface low heads into MO by Wednesday evening and heads for the
Chicago area by early Thursday before crossing IN and OH Thursday.
500 mb height falls are shown to fall Wednesday night by about 100
meters and then another 100 meters during the day Thursday.
Confidence on the evolution of this upper trough is fairly high,
though there are some minor timing differences shown in the global
ensembles that could impact the precipitation type over the ridges
early Thursday (see next paragraph).  Decent warm advection appears
likely along with moisture transport from the Gulf of Mexico,
resulting in another period of welcome rains. Probability of 48 hour
QPF exceeding 0.10" is nearly 100%. The 25th to 75th percentile 48
hour QPF ranges from about 0.30 to 0.60" in the Pittsburgh area.
While most of the precipitation is likely to fall during the day
Thursday, lingering light rains are possible Thursday night into
Friday.

While most of this event will be rain, there is a window
especially for eastern Preston and eastern Tucker County WV
where the precipitation may arrive as freezing rain or snow late
Wednesday night or Thursday morning. Tds are likely to be in the
teens and 20s with temperatures near freezing, resulting in wet
bulb cooling as the precipitation arrives. NBM Probability of
freezing rain is in the 20-50% range from roughly 4-10 am
Thursday morning especially in far eastern Tucker County.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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 /06Z WEDNESDAY THROUGH SUNDAY/...
VFR under the influence of high pressure is highly likely
through the TAF period. Warm, moist advection in developing
southwest flow aloft will increase cirrus after 12z while high
pressure to the NE fosters easterly surface wind that
occasionally gusts to 15-20kts this afternoon.

The expectation is for lowering of ceiling heights after 00z as
a upper trough and associated surface low approach from the
west. Impacts are not expected until after the TAF period.

.Outlook...
A surface warm front and the encroaching upper trough will
foster high probabilities for rain and lowering ceilings as it
moves west to east after 09z Thursday. Latest guidance suggests
a 40-50% probability for IFR conditions (mainly via ceilings)
after 12z Thursday at most terminals with improvements tethered
to post-warm frontal passage (though likely remaining around
MVFR cats).

The upper level trough will drop ESE late Thursday into Friday
morning with residual cold advection in NW flow lingering in the
area. This may favor prolonged MVFR conditions and spotty light
rain showers/drizzle before VFR returns later Friday as high
pressure returns.

&&

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

&&

$$

SYNOPSIS...Craven
NEAR TERM...Craven/Milcarek
SHORT TERM...Craven
LONG TERM...Craven
AVIATION...Frazier