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FXUS61 KPBZ 291021 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 521 AM EST Wed Nov 29 2023

SYNOPSIS
Single digit wind chill values this morning will quickly warm toward above normal temperature by Thursday under the influence of high pressure. A series of shortwaves will cross the region starting Friday into early next week, providing periodic rain chances and seasonably warm temperature.

NEAR TERM /THROUGH TONIGHT/
530am update...
Tweaked sky coverage to account for exiting lower clouds to the east and incoming warm advection induced clouds from the west, which aren't quite being handled well by available model data.
Otherwise, no other notable changes were needed at this time.

Rest of discussion...

As surface high pressure positions its center over the Carolinas, height rises will be experienced above the Upper Ohio River Valley today; the combination will fuel warm advection that raises area high temperature approximately 10 degrees from Tuesday's afternoon readings. Residual shortwave movement within the eastward moving upper trough will offer daytime mid-level cloudiness, but lack of deeper moisture/lift will leave the region dry.

Upper flow will experience shortwave ridging overnight as surface high pressure remains over the Carolinas. This will result in continued improvements in area low temperature toward the seasonal average.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
Warm advection will persist into Thursday with little change in surface pressure orientation while height rises aloft continue in response to a deepening trough over the south central plains.
Moist advection ahead of this system is expected to increase area high clouds, but enough insolation/warm advection should leave area high temperature near to slightly above the daily average.

A northern stream trough will cross overnight while the south central plains trough begins to lift northeast. An area of convergence (acting as a pseudo warm front) between the system may offer low probability light rain chances that favor eastern OH to northwest PA, then model trends may keep the greater frontogenetic forcing/lift far enough west as to further lower precipitation chances.

Rain becomes likely through the day Friday as the southern stream trough crosses the region while experiencing notable deterioration in organization (becoming more of a weak open wave within southwest flow). Mean rainfall amounts are expected to be near half an inch, but scenarios remain for lower (and less likely, higher) totals if synoptic forcing continues to wane and/or becomes better positioned outside the forecast area.
Light rain and potentially drizzle will remain possible overnight Friday as the region remains situated north of the warm front (as the surface low is expected to stall in forward movement). But confidence lowers given variability in model depictions. The pattern, regardless, will support near to above normal temperature for both the daytime/nighttime periods Friday.

LONG TERM /SATURDAY THROUGH TUESDAY/
Ensemble models are trending toward a solution of a secondary shortwave within southwest flow to rapidly follow the Friday wave, aiding the further northeast movement of the surface low.
This could offer additional rain chances early morning to the early afternoon (depending on low track), before subsidence and high pressure promote drier weather by Saturday evening.
Temperature will remain above the daily average as southwest flow persists.

The broad west coast trough/east coast ridge type pattern previously described will break down with the next upper trough passage. Timing and synoptic details of that trough remain elusive as well as any additional shortwave movement before its arrival. Confidence is high the trough axis should arrive by Monday afternoon and generally to persist through midweek.
Though ensemble spread remains elevated through this period, there is enough consensus to suggest the following basic trends:

- Above normal temperature will remain Sunday into early Monday.
- Temperature will trend near to below normal by Wednesday.
- Precipitation is likely to occur from Sunday through the middle of next week, but timing and extent of any dry periods remains fuzzy.

AVIATION /10Z WEDNESDAY THROUGH SUNDAY/
Patchy VFR stratocu will affect DUJ through around 14Z before exiting. Otherwise, mid level clouds will quickly overspread the region through the morning as warm advection occurs ahead of the next approaching shortwave.

Cigs should lower to 5kft-6kft by late morning as this weak wave crosses the region. Moisture is lacking, so no precipitation is expected. The shortwave will exit the region by evening, with clouds clearing under shortwave ridging. Mixing and a tight surface pressure gradient should result in gusty SW wind later this morning through the afternoon, before mixing and wind gusts subside after sunset.

OUTLOOK
VFR is expected Thu under high pressure. Restrictions and rain return Thu night through Sun with crossing low pressure.

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

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