PBZ issues Area Forecast Discussion (AFD) at Oct 12, 5:42 AM EDT258
FXUS61 KPBZ 120942
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
542 AM EDT Sat Oct 12 2024
.SYNOPSIS...
Dry and warm weather will continue today. Shower and
thunderstorm chances return tonight through Sunday night with
crossing low pressure. Much cooler and unsettled weather is
then expected through Wednesday with a series of crossing
disturbances.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Dry weather today with increased cloud cover
-------------------------------------------------------------------
Made a few adjustments to the hourly temperature and sky trends
based on the latest observations for the early morning update.
Otherwise, a surface ridge of high pressure was across the
Appalachians to the Upper Ohio Valley region. A cold front was
located across the Lower Great Lakes region. The surface ridge
will slide south as the weak cold front drops southward across
the region. Mid and high cloud cover was observed upstream with
the front, and these clouds should increase across the region
today as the front approaches and then stalls across OH into
southern PA.
Little upper support for ascent was associated with the front,
so no rain is expected for most areas, though some increase in
moisture and convergence along the front could result in an
isolated shower in the vicinity of PHD this afternoon. High
temperatures are expected to be around 5 degrees above average
for this time of the year.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
KEY MESSAGES:
- Showers and possible strong thunderstorms Sunday and Sunday
evening
- Much cooler with scattered showers through Sunday night
through Monday night
-------------------------------------------------------------------
A digging shortwave trough is progged to track from the Upper
Midwest tonight, as surface low pressure develops in response
across IL and IN, SE of the trough. This low will pull the
stalled cold front back north as a warm front later tonight into
Sunday morning as it tracks eastward. With increasing moisture
and ascent, enhanced by an approaching low level jet, showers
are likely north of PIT, with lower shower chances to the south,
south of the front. A thunderstorm will also be possible with
the low level jet, and minimal elevated instability (Showalter
indices of 0 to -1 across NW PA through OH.)
The digging shortwave will continue to advance across the
Midwest and Great Lakes region Sunday, as the surface low tracks
across OH through PA. The low will pull a cold front across the
region during the afternoon and early evening hours.
Wind profiles increase through the day Sunday with an
approaching jet. Gusty winds around 30-35mph are possible with
mixing during the afternoon. A narrow band of instability is
progged to develop just ahead of the cold front during the mid
to late afternoon, with mean MU CAPE values around 500 j/kg
generally S-SE of PIT. 0-6km shear is expected to increase to
between 40 and 50kt at the same time. Model soundings indicate
a mid level cap as well, eroding as FROPA occurs. This cap
should help limit thunderstorm development, though a broken
line of showers and embedded thunderstorms are expected along
the front. More convectively enhanced showers or organized
thunderstorms could tap the increased wind field aloft,
resulting in a potential for damaging wind gusts S-SE of PIT.
The Storm Prediction Center has placed this area in a Marginal
Risk (level 1 out of 5) for severe storms Sunday afternoon and
evening. Will highlight this potential in the Hazardous Weather
Outlook.
Showers and thunderstorms will taper off Sunday evening after
FROPA. Showers should increase in coverage again late Sunday
night and Monday as the initial upper trough axis crosses the
region, and cold advection occurs. The trough is progged to
deepen into a closed low across eastern Canada later Monday and
Monday night, as additional shortwaves rotate around it. This,
and cold NW flow off of the Great Lakes, will maintain scattered
to numerous showers across the region through Monday night. A
few snow flakes could also mix in across the higher terrain
areas, as 850mb temperatures drop to around -2 deg C.
Gusty winds are expected through much of the period, generally
ranging from 20-30mph.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
KEY MESSAGES:
- Cooler and unsettled weather through mid week
- Dry and warmer toward late week
-------------------------------------------------------------------
Model ensembles indicate the upper low will remain across the NE
CONUS through midweek, before opening into a trough and exiting
eastward later Wednesday. Continued cold NW flow off of the
Great Lakes, and shortwaves rotating around the low, will
maintain scattered showers across the region. Temperatures at
850mb are progged to range from -2 to -4 deg C through midweek,
and some snow could mix in at times across the higher terrain
areas of the Laurel Highlands and WV.
A ridge, between the exiting trough the the east, and a western
CONUS trough, will build across the region by late week. This
will result in dry and warmer weather returning to the region.
&&
.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
A passing disturbance over the Great Lakes will increase cloud
coverage from north to south over the next 6 hours. However, the
probability of VFR cigs prevailing, despite this noted
disturbance, is high (above 95%); cloud deck will likely remain
above 5kft. LLWS for FKL/DUJ is expected through 10Z; 850mb
with this noted shortwave range from 35kts to 40kts.
The potential for fog is low given an increase in wind and
clouds.
VFR is expected to persist through at least 06Z Sunday. A few
Hi- Res model ensemble suggest precip over eastern Ohio between
18Z and 23Z Saturday along a warm front. However, subsidence
near the surface may negate measured precip.
.Outlook...
The probability of precipitation increases between 06Z and 09Z
Sunday as a low pressure system ejects out of the Midwest.
Elevated winds aloft may range from 35kts to 40kts early Sunday;
the mention of LLWS may be needed for a few terminals.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...Hefferan
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 12, 5:42 AM EDT---------------
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