PBZ issues Area Forecast Discussion (AFD) at Aug 11, 2:03 PM EDT366
FXUS61 KPBZ 111803
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
203 PM EDT Tue Aug 11 2026
.WHAT HAS CHANGED...
The Flood Watch has been expanded northward to include
additional counties in eastern Ohio, northern West Virginia,
and far southwest Pennsylvania. Some models are hinting at a bit
more northerly track to the expected Tuesday night MCS, and
this trend will be monitored closely.
&&
.KEY MESSAGES...
1) Storms will bring near-daily flood and severe potential
through at least Wednesday.
&&
.DISCUSSION...
KEY MESSAGE 1...
Ongoing MCS will continue to cross the region and depart by
sunrise. Although some gusts to 40 MPH will continue to be
possible, the decrease of downdraft CAPE and the unfavorable
lapse rates have pretty much ended the severe threat for
tonight. Flash flooding threats will continue however, as pockets
of heavy rain can be expected in the 1.7 to 1.9 inch
precipitable water airmass, with training thunderstorms
producing localized bands of 2-3 inches of rain in an hour or
two. This threat should end by sunrise, with a lull in activity
in the subsidence behind the MCS.
Although scattered activity may develop this afternoon in the
destabilizing and still anomalously moist air mass, the main
concern is the next potent MCS that is forecast to begin to
organize over the Upper Midwest today and track southeast across
IN/OH and towards the Ohio River. While previous CAMs runs kept
this complex mostly off to our south and west, recent HRRR runs
are starting to trend towards a more northward track,
potentially impacting a larger portion of eastern Ohio, northern
West Virginia, and far southwest Pennsylvania around 00Z
Wednesday. However, HREF/REFS continue to keep the richer CAPE
to the southwest of CMH, with a gradient just to the southwest
of the CWA that may represent the previously favored track. The
current SPC outlook has a Slight (level 2 of 5) Risk for mainly
damaging wind gusts south of a PHD/HLG/MGW line. If current
HRRR trends continue and are supported by additional guidance,
this risk area may need to be nudged north with time, with
perhaps the introduction of an Enhanced (level 3 of 5) Risk to
in and around the ZZV area at least. If such an expansion
occurs, the chances of more significant wind gusts (into the
65-75 MPH range) would increase in the newly upgraded Enhanced
area.
Regarding future rainfall, HREF/NBM means have generally 1 to
1.5 inches in the area from around Pittsburgh to the south and
west through 12Z Wednesday. HREF maximums suggest 2 to 3 inch
stripes are possible in the region, with potential for more
storm training. The ongoing Flood Watch was extended northward
another row of counties, but still remaining south of Pittsburgh
at this time. Further northward expansion is possible later
today.
It must continue to be said that this entire forecast period
will remain low confidence, with each subsequent storm/threat
chance tied to the prior. Monitoring the forecast frequently
may be imperative. Wednesday and Thursday will bring additional
chances of severe and flash flooding, though chances of systems
slowly decrease through time as the development region is
expected to drift south into the central Appalachians.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Low confidence forecast as tempo for showers may not
materialize given upstream trends. In addition, CIGS could be
higher than IFR overnight at some airports.
CIGS should settle into the VFR category this afternoon after
the batch of rain moves through. Scattered storms could affect
FKL and DUJ while the complex over western Ohio should impact
ZZV. Elected to carry a tempo to cover this for several airports
during the 20-02Z window. Most of the time it will be dry. The
highest confidence of an airport seeing a thunderstorm would be
FKL/DUJ/ZZV.
The other challenge is how widespread the IFR clouds will be
tonight? The consensus of the guidance suggests all sites drop
below IFR to threshold B mins. It was hard to refute the
guidance, but something we will fine tune with the next forecast
suite.
VFR Wednesday once any low clouds lift with the northern
airports of FKL and DUJ owing to scattered cirrus otherwise more
stratocu.
Outlook...
Wednesday should be mainly dry for airports with at worse a
brief drop in a shower or storm. Activity is on the uptick
Thursday with showers and storms before quieting down to VFR
weather save for patchy morning fog at a few terminals.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...Flood Watch through Wednesday morning for OHZ039-048-057-058-
068-069.
WV...Flood Watch through Wednesday morning for WVZ012-021-509>514.
&&
$$
DISCUSSION...Milcarek
AVIATION...McMullen
Source:
PBZ issues Area Forecast Discussion (AFD) at Aug 11, 2:03 PM EDT---------------
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