PBZ issues Area Forecast Discussion (AFD) at Nov 9, 1:25 AM EST572
FXUS61 KPBZ 090625
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
125 AM EST Sat Nov 9 2024
.SYNOPSIS...
Dry weather is expected through Saturday. Low pressure will
support widespread rainfall Sunday into Monday. Uncertainty
increase into next week with possible rain chances returning by
mid-week.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KEY MESSAGES:
- Overnight lows right around normal.
-------------------------------------------------------------------
The aforementioned stratocumulus deck remains confined to areas
north of I-80 with a notable fetch off Lake Erie. There are
still expected to clear through the night as winds veer towards
the northeast. Clear skies prevail elsewhere besides some
passing high clouds.
To match current observations, dew points were dropped closer to
the 10th percentile. Additionally, clear skies and calming winds
overnight led to nudging low temperatures down slightly.
.. Previous Discussion..
Cold advection aloft in northwest flow behind the trough likely
develops a stratocu deck for part of the overnight hours, but
as advection becomes more neutral in the latter half of the
night, should see cloud coverage erode and hi res ensemble
spread depicts this nicely with the higher end of the
distribution envelope signaling a return of partly cloudy to
mostly clear skies.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Dry start to the weekend with above-normal temperatures.
- High confidence in widespread wetting rainfall on Sunday.
-------------------------------------------------------------------
Upper ridge axis shifts overhead on Saturday and amplifies
downstream of a closed low across the Plains. Warm advection aloft
with the building ridge atop easterly surface wind will push 850 mb
temperatures to 8-12C, higher southwest and lower northeast, which
will push highs again a couple degrees above normal. Still dry low
levels and localized downsloping effects off of the ridges will
allow for dew points to mix out again in the afternoon and minRH
values down to the upper 20/low 30 percent range. Lesser wind
gusts should preclude widespread fire weather concerns, but
conditions will warrant monitoring. Clouds increase late
Saturday as deep layer moisture ramps up ahead of approaching
low pressure. Warm advection will keep overnight lows in the
upper 30s-low 40s.
Deep southwest flow will provide a strong pull of Gulf and remnant
Rafael moisture on Sunday with integrated vapor transport values 2-4
SD above normal and ensemble mean precipitable water near 1.3" which
is near the daily maximum value. As low pressure lifts through the
Great Lakes region, widespread rainfall is expected to arrive in the
morning hours. The most steady rain likely comes Sunday afternoon as
an 850 mb jet encroaches and enhances low level convergence. Current
ensemble probability for a wetting rain (at least 0.10") is very
high at 95-100% areawide. Similarly, at least 0.25" is 90+% with
a 60-80% chance of a half an inch. The higher end (90th
percentile) of the goal posts has continued to sit around an
inch and is likely contingent on capitalization of whatever
marginal instability can develop; instability likely won't be
surface-based given the low-level warm advection regime, so any
severe weather threat is low. The system will be progressive
overall, but wouldn't rule out some localized totals nearer to
the 75th-90th percentile in some of the maximized higher
rainfall rates.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:
- Low confidence rain chances for the beginning of the week.
- Better rain chances come mid-week but still some uncertainty.-
- Highs a few degrees above normal.
-------------------------------------------------------------------
Some showers may linger into Monday behind departing low pressure as
a weak secondary trough moves through, but ensemble clusters suggest
increasing uncertainty with the upper level pattern to start out
next week as an additional upper wave follows quickly behind the
original one from Sunday. Some clusters merge these waves while
others favor a flatter, more progressive pattern. A slower departure
would favor cooler temperatures and lingering precip chances through
Monday night while a faster pattern favors warmer, drier conditions.
Overall consensus is that high pressure and upper ridging briefly
return which favors still above normal temperatures through mid-
week. Another better chance for rain may come sometime Wednesday
into Thursday with another round of low pressure, but significant
differences among the ensembles suggests a low confidence forecast
by this point.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions will prevail through the TAF period with light
winds gradually veering from northerly to easterly through the
morning. High/mid clouds will push into the area Saturday night
in advance of the next system.
.Outlook...
Rain and restrictions will likely overspread the region after
12Z Sunday.
A passing cold front early Monday will decrease the potential
for rain. However, restrictions may linger into late Monday
morning due to residual low-level moisture and cold advection.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...MLB
NEAR TERM...MLB/Milcarek
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Rackley/88
Source:
PBZ issues Area Forecast Discussion (AFD) at Nov 9, 1:25 AM EST---------------
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