PBZ issues Area Forecast Discussion (AFD) at Oct 18, 7:33 AM EDT547
FXUS61 KPBZ 181133
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
733 AM EDT Fri Oct 18 2024
.SYNOPSIS...
High pressure will dominate into early next week providing dry
weather and temperatures rising to above normal. The next chance
for rain may return with a passing disturbance mid-week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Sunny with widespread highs in the middle to upper 60s
expected region-wide Friday.
-------------------------------------------------------------------
Update focused mainly on freshening up temperatures, which are
varying a bit based on urban effects and minor bouts of low-
level mixing. Valley fog is prominent along the major rivers, as
would be expected this time of year in clear and chilly
conditions. The fog will lift by mid-morning, leaving abundant
sunshine and above-normal temperatures. Frost/freeze headlines
will drop off at 9 AM.
Previous discussion...
Clear skies (outside of river valley fog) and light winds are
expected to prevail through the day Friday across the region. Fog is
expected to lift a couple of hours after sunrise and temperatures
are expected to respond quickly. The 00z sounding noted 850mb
temperatures around 5C. The newest HREF run in agreement with other
short term modeling has probabilities >90% of 850mb
temperatures rising to 10C by early Friday afternoon. This is
accompanied with an absurd rise in heights for this time of
year. LREF probabilities are north of 60% for us to reach 590dm
500mb heights by 2pm Friday. These probabilities rise to near
100% by 8pm. These factors combined with our clear skies set up
a perfect chance to maximize our daytime heating. This could
have much of the region eyeing high temperatures in the middle
to upper 60s with the chance to strike 70 degrees not off the
table. Our high of 61 degrees Thursday was north of the 95th
percentile on the 07z NBM and was in the 90th percentile from
the 13z run. As it stands now the 90th percentile from the NBM
is 68 degrees. The 95th percentile is 69 degrees. This will be a
far cry from highs near 50 the area experienced just two days
ago. A lower sun angle and shorter duration of daylight will do
what they can to hinder this process but confidence in this
solution is growing.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
KEY MESSAGES:
- Additional frost/freeze headlines possible Friday night.
- Dry weather with a warming trend and highs above normal.
-------------------------------------------------------------------
The setup will favor efficient radiational cooling conditions
again Friday night with high pressure overhead providing clear
skies and calm wind. With dew points progged to be in the low to
mid 30s, probabilities for <32F MinTs are subsequently lower and
only max out around 60% primarily in our northwest zones
coincident with the lowest dew points. When jumping to <36F,
those probabilities are higher at 60-80% outside of urban areas
(30-50% there). One caveat could be if dew points can very
efficiently mix out Friday afternoon, we may see a potential
lower floor for MinTs.
High confidence forecast is in store for the weekend as ensemble
clusters exhibit little deviation from strong upper ridging and
surface high pressure in control. The result will be a beautiful
October weekend to enjoy any seasonal outdoor festivities. 500
mb height anomalies reach to +2.5 SD up to 590 dm and ensemble
probability for 850 mb temperatures >12C both days this weekend
sit at 70-90%. The decreasing sun angle will limit the ceiling,
but low level warm advection, mostly sunny skies, and afternoon
mixing out of dew points will still support highs reaching well
above climatological normal (low 60s for PIT) in the low 70s.
Lows will moderate as well and, provided the growing season has
not ended, Saturday night appears the last of frost/freeze
concerns looking ahead through most of the coming week with
probabilities for <36F around 40-60% outside of urban areas.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
KEY MESSAGES:
- Remaining dry and warm through early week.
- Low probability rain chances return by mid-week.
-------------------------------------------------------------------
Upper ridging and surface high pressure remain in place on Monday
with high confidence, though the noted difference will be the
placement of the high which all ensembles agree on migrating to the
east. This favors a southerly return flow setup, albeit weak, come
Monday, which points toward increasing moisture while an upper
trough digs across the Rockies. Probabilities point toward Monday
and Tuesday being the warmest of the period with a >90% chance for
70F Monday and even a 70-90% chance of 75F on Tuesday from PIT and
south.
Some disagreement then comes into play as ensemble clusters
differ on the progression of the upper trough; the general
consensus is a flattening as it ejects east and takes on an open
wave when it arrives locally but with differences on
amplification and timing. A more amplified solution would lead
to better moisture return and rain chances, but even that
solution isn't much to write home about with only a 20-40%
chance of exceeding a tenth of an inch of rain. Nearly 50% of
the cluster QPF distribution is confined to less than 0.2" with
a tail toward a half of an inch likely contingent on maximizing
aforementioned deeper layer moisture return. Otherwise,
temperatures look to moderate back closer to normal for the
latter half of the week.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
VFR conditions through the TAF period will only be marred by
river valley fog near FKL, with IFR expected at that terminal
through 13Z or so. Otherwise, high pressure provides a clear sky
and light wind.
.Outlook...
High pressure should maintain general VFR conditions through the
weekend and into early next week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory until 9 AM EDT this morning for PAZ020-021-029-
031.
Freeze Warning until 9 AM EDT this morning for PAZ007>009-
013>016-022-073>078.
OH...Frost Advisory until 9 AM EDT this morning for OHZ039>041-
048>050-057>059-068-069.
WV...Frost Advisory until 9 AM EDT this morning for WVZ001>004-012.
Freeze Warning until 9 AM EDT this morning for WVZ021-509>513.
&&
$$
SYNOPSIS...MLB
NEAR TERM...CL/AK
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...CL
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 18, 7:33 AM EDT---------------
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