PBZ issues Area Forecast Discussion (AFD) at Sep 26, 3:53 AM EDT783
FXUS61 KPBZ 260753
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
353 AM EDT Thu Sep 26 2024
.SYNOPSIS...
Gradual lowering of precipitation chances is expected today
Thursday before a potentially unsettled pattern develops Friday
into early next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Morning showers possible.
- Mostly dry by afternoon seasonable temperatures
-------------------------------------------------------------------
Minor height rises are expected today as the area remains stuck
between a northern upper low, moving across southern Canada,
and a western upper low, which will slowly dig toward the
Tennessee valley today. The northern stream energy will have
more influence over our weather today as it will suppress the
moisture and energy streaming northward on the eastern side of
the western 500mb low. In addition, a weak cold front will be
forced southward through the region as the flow aloft becomes
more northerly. With the deep moisture and best forcing blocked
to our south, most of the region should dry out after some
scattered morning showers. Don't expect much of a break in the
cloud cover and temperatures remain above normal.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
KEY MESSAGES:
- Potential for increasing influence from the remnants of Hurricane
Helene
-------------------------------------------------------------------
Variation in outcomes increase Friday, and are largely defined
by the positioning/movement of Hurricane Helene remnants in
conjunction with the west TN closed 500mb flow. Ensemble means
suggest rain chances starting Friday morning south of Pittsburgh
with the initial outer bands of the large area of low pressure.
This assumes the surface low reaching the western NC/SC border
Friday morning and lifting towards eastern KY by mid-day. Other
higher-resolution model forecasts are slower and farther west
with the low track, which favor the outer bands staying south of
the region. Current forecast represents a blend of the two with
higher/lower PoPs south of Pittsburgh possible in scenario 1/2,
respectively.
Low positioning will also influence surface gradient and the
onset of SE wind increases. Confidence is high for slightly
above average temperature continuing while cloud cover remains
plentiful.
Overall, little change for Saturday as the upper low fills and
drifts eastward.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
KEY MESSAGES:
- Rain chances will continue through the weekend, but no day
looks like a washout.
-------------------------------------------------------------------
Ensembles are in fairly good agreement in the broad idea of
continued interaction between the TN closed low and Hurricane
Helene remnants Sunday into Monday. The combined low area will
slowly weaken before drifting SE into early next week. Expect
periodic rain chances, abundant cloud cover, and above normal
temperature during this period. Despite the agreement, large
variations exist in the finer scale details of mesoscale
banding, jet placement, and low positioning that will greatly
determine timing/coverage/intensities of rain showers. Though
any given period could see showers, the limitations of
resolution for global models and general pattern recognition
suggest dry conditions are more likely than not with smaller
windows of rain that the forecast lends itself to.
Ensemble means favor a northern stream trough kicking the
sagging low out of the region by mid-week and ushering an
airmass change. That said, scenarios remain on the sagging low
staying farther south while ridging develops near the Great
Lakes; this would foster drier and warmer than forecasted
conditions.
&&
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
Mainly VFR is expected through the early overnight, with
lingering MVFR at FKL and DUJ, ahead of another shortwave
embedded in SW flow on the eastern side of an upper low across
the Midwest. Expect occasional showers to move across the area
through overnight as this next wave crosses the region.
Deterioration to MVFR areawide is expected as the lower levels
become saturated. Moisture pooling around a weakening surface
boundary should result in IFR at ZZV, FKL and DUJ.
Rain should diminish through the morning as the shortwave
exits. A gradual improvement to VFR is expected by mid to late
afternoon as mixing results in an increase in ceiling heights.
.Outlook...
Light rain and restrictions are possible Friday, mainly south of
FKL-DUJ, as moisture streams north ahead of tropical system
Helene. VFR is expected Friday night and early Saturday before
an upper low spreads rain and restriction chances back across
the region late Saturday through early Monday.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...22/Frazier
NEAR TERM...22
SHORT TERM...22/Frazier
LONG TERM...Frazier
AVIATION...WM/Rackley
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 26, 3:53 AM EDT---------------
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