PBZ issues Area Forecast Discussion (AFD) at Oct 9, 4:18 AM EDT703
FXUS61 KPBZ 090818
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
418 AM EDT Wed Oct 9 2024
.SYNOPSIS...
Lots of sunshine this week with a slow warming trend beginning
Thursday into the weekend. There is potential for the fall's
first widespread frost later come dawn Friday morning. The next
shot at rainfall arrives later Sunday and it will be light and
mainly communities closer to Lake Erie.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Continued dry weather and near normal temperatures.
-------------------------------------------------------------------
A weak surface trough coming through the area early this morning
will increase cloud coverage north of PGH. Farther south, skies
are expected to remain mainly clear. Dewpoints largely in the
lower 40s should limit patchy frost potential.
Differentials between the air and river temps will once again
allow for river valley fog to develop early this morning.
Boundary layer temps warm a little while H8 temps cool slightly
which supports a near identical max temperature forecast
today as observed on Tuesday. There could be scattered cu in
the northwest flow off of Lake Erie for locations north of I-80.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
KEY MESSAGES:
- Continued dry weather and seasonal temperatures.
- Frost potential in some areas Thursday and Friday mornings.
-------------------------------------------------------------------
Benign weather through this period as well. The biggest challenges
will be max temperatures Thursday. This is where the greatest
spread from the 25th-75th percentile exits /9-11F/. NBM mean is a
few degrees warmer than the mean from ECMWF and GFS. Looking at
violin plots from the NBM, the reason for the uptick in highs
Thursday is the bias correction, which puts values into the lower
60s for the lower elevations with upper 50s toward the Allegheny
National Forest and north of I80.
We continue to stress potential for frost / freeze Thursday night
into Friday over a decent area, unlike normal cold spots this
morning. Joint probabilities of lower than 36 degrees and wind less
than 5 mph are between 25-50% in northwest PA / Clarion - Forest -
Jefferson counties/ with less than 20% elsewhere. If you take away
the wind from the prob it jumps to 40% to 70% from rural eastern
Ohio and northwest central PA. Will continue to message this in the
hazardous weather outlook as well as other means. It doesn't appear
the Pittsburgh, Morgantown, or Zanesville areas will get a frost, so
confidence remains high in that regard. For what it is worth, NBM
10th percentile has a freeze or just above for most of the region.
This would be worse case scenario for those with sensitive plant
interests.
With surface flow becoming southerly given the juxtaposition of the
surface anticyclone afternoon temps begin their climb back above
normal Friday with widespread 60s and lower 70s south of the Mason
Dixon line expected under lots of sunshine. The gradient flow near
the surface keeps the boundary layer from decoupling as much as
previous nights, so values come dawn Saturday could be as much as
ten degrees warmer than the former.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Dry weather continues through at least through Saturday;
light rain possible for Sunday and Monday mainly I80 and north.
- Above normal temperatures this weekend followed by another cooldown
early next week.
-------------------------------------------------------------------
Mid level height falls allowing an upper air disturbance and wave of
low pressure to pass late Sunday into Monday. There remains
questions on the amount of moisture this system can tap.
Probabilities from the NBM of greater than 0.05" of QPF range from
25% to 45% along and north of an Indiana to Pittsburgh to New
Philadelphia line. If you crank up the threshold to a tenth of an
inch /wetting rain/ values drop by 10-15% across the board. So what
does this mean? Well confidence is still low in measurable QPF, but
the greatest chance is north of the aforementioned line. Chance to
likely pops closer to the lake remain the best course of action at
this time. This by no means is a washout or drought buster for the
region. In fact, the lowest chance of rain the next seven days
resides across the area that needs it the most <insert eye open
emoji>.
The coolest air so far this season arrives next week with above
average confidence of below normal temperatures and potential
widespread frost monday night into Tuesday...if clouds clear.
NAEFS and GEFS both indicate H5 heights one to two standard
deviations below normal as a modest positively tilted mid level
trough sweeps through the Great Lakes Day 6 and 7. Much like the
system this weekend, there is not a strong surge of moisture in the
warm sector, but more so on the backside when northwest winds pick
up moisture from the lakes. Not much change in the forecast with
continued chance pops for a good part of the region. Values
decrease as you head south.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
A surface trough was moving across the the Lower Great lakes and
Upper Ohio Valley region early this morning. Mainly mid level
clouds were observed with this trough. Wind around 5kt, and
patchy mid level clouds, should help limit the development of
river valley fog this morning.
The trough will exit the region this morning, with cold
advection aloft. This will steepen low level lapse rates. With
these lapse rates, and low convective temperatures, expect a
scattered diurnal CU layer to develop by mid morning, along with
WNW wind gusts up to 20kt.
Wind will diminish this evening as mixing ends, though cool NW
flow will maintain scattered to broken VFR stratocu across the
region overnight.
.Outlook...
Outside of any early morning river valley fog, VFR is expected
through Saturday under building high pressure. Restriction
potential returns Sunday with a crossing cold front.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...McMullen
NEAR TERM...88
SHORT TERM...88/McMullen
LONG TERM...McMullen
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 9, 4:18 AM EDT---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
