Special Weather Statement, NWS State College, PA

Area Forecast Discussion
National Weather Service State College PA
310 PM EDT Fri Aug 20 2021

.SYNOPSIS...
A cut off upper low will drift very slowly southeast across the
region over the next few days, reaching the Delmarva Coast
Saturday night. This weather feature, along with deep, tropical
moisture being captured from Tropical Storm Henri will likely
bring some moderate rainfall amounts of rain across the Eastern
Half of the state Saturday afternoon and night.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Partly sunny conditions previling across roughtly the western
half of central PA this afternoon, while mostly cloudy skies
prevail shrink over eastern sections as the mid-high cloud
shield lifts out of central PA. Expect isold to sct shra into
this evening under the weak upper low, with just a rogue
lightning strike expected as vertical extent of storms is
limited by sfc heating/CAPE. Amounts will be light, but some
areas could see a quick tenth or two under a heavy downpour.

Aforementioned upper low will slowly drift eastward across the
state to start the weekend, leading to a good chance of showers
and isolated thunderstorms Saturday, especially in the
afternoon.

Mins tonight will range to around 60 north to the lower 70s
southeast. Areas of valley fog should be prevalent after
midnight and dissipate shortly past sunrise.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
We are still watching developments on the eventual track of now
Tropical Storm Henri, forecast to become a Hurricane by Saturday
afternoon, as it targets southern New England. Latest model
forecasts have shifted Henri's track westward into central and
eastern Long Island and up into CT and western MA...with some
outliers even farther west. This is to be expected 36 to 48
hours out, but particularly given the upper flow defined by the
weak upper low over PA within a large scale upper ridge
interacting with tropical system along the coast with a highly
amplified upper ridge over the western Atlantic. Further
adjustments are expected, which could increase eventual rainfall
to areas east of central PA

With this in mind, we are still expecting some moisture to be
drawn into eastern PA by Henri from the western Atlantic. Basin-
average rainfall amounts on the synoptically favored/western
side of Henri should be focused over the Susquehanna Valley and
points east on Saturday. WPC has a little over the eastern
third or so of the CWA in a MRGL risk for heavy rain/localized
urban/small stream flooding Saturday/Sat evening.

Localized rainfall amounts could exceed 1.00" across the
eastern half of PA, while the areal coverage of showers over the
west should be much more spotty with light amount of QPF.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Will continue to watch Henri's evolution through the rest of
this weekend, in concert with the slow eastward progression of
upper trough axis from PA towards the east coast. Henri will
make a run at southern New England and perhaps turn farther left
towards central Long Island or southern/southwestern CT. We
expect there to be an area of enhanced rainfall Saturday night
and Sunday somewhere between Henri and the gradually departing
trough axis, with this region likely to the east/northeast of
central PA, but this area can shift westward. The current
expectation is that showers will ever so slowly trudge eastward
by Sunday, with our western zones (Allegheny highlands) likely
to see improvement sooner than the Susquehanna Valley.

Early next week, in the big picture, Henri should ultimately get
swept eastward into the north Atlantic by westerlies arriving
from the Ohio Valley, with rising heights aloft over the
eastern U.S. This should lead to seasonably warm late summer
conditions, with any convective coverage isolated-widely
scattered in nature, and confined to the afternoon/early evening
hours.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Widely scattered showers may produce brief, local visby
restrictions through the remainder of the afternoon. Otherwise,
VFR should prevail. Based on latest radar trends, the eastern
3/4 of the airspace has the highest probability of an
isolated/brief shower or t-storm. Expect low VFR cumulus to fade
along with shower activity by tonight. This will set the stage
for fog/stratus development late tonight into early Saturday
morning. Model guidance remains bullish on IFR conditions
impacting the northwest 1/2 of the airspace. Used a blend of
persistence and LAMP which suggests potential for LIFR/VLIFR
conditions near or below airfield minimums during the predawn
and early morning hours Saturday. Expect low clouds and fog to
break into MVFR to low VFR cigs by midday with an increasing
chance of showers and t-storms into Saturday afternoon.

Outlook...

Sun-Wed...Restrictions possible in scattered afternoon showers
and isolated t-storms.

&&

.CLIMATE...
Daily rainfall records were broken on August 18, 2021
Altoona: 3.69" (previous was 1.24" set in 1955)
Bradford: 1.98" (previous was 1.11" set in 1973)
Johnstown: 2.01" (previous was 1.11" set in 1932)

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

SYNOPSIS...Lambert/DeVoir/Gartner
NEAR TERM...Jurewicz/Lambert/DeVoir
SHORT TERM...Lambert/DeVoir/Fitzgerald
LONG TERM...Jurewicz
AVIATION...Steinbugl/Banghoff
CLIMATE...

Hazardous Weather Outlook
National Weather Service State College PA
923 AM EDT Fri Aug 20 2021

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056-057-063-064-211330-
Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield-
Northern Centre-Southern Centre-Cambria-Blair-Huntingdon-Mifflin-
Juniata-Somerset-Bedford-Fulton-Franklin-Tioga-Northern Lycoming-
Sullivan-Southern Clinton-Southern Lycoming-Union-Snyder-Montour-
Northumberland-Columbia-Perry-Dauphin-Cumberland-Adams-
923 AM EDT Fri Aug 20 2021

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

PAZ058-059-065-066-211330-
Schuylkill-Lebanon-York-Lancaster-
923 AM EDT Fri Aug 20 2021

This Hazardous Weather Outlook is for central Pennsylvania.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Scattered afternoon thunderstorms on Saturday could produce
localized flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Special Weather Statement
National Weather Service State College PA
633 PM EDT Fri Aug 20 2021

PAZ019-026-027-202300-
Huntingdon PA-Mifflin PA-Southern Centre PA-
633 PM EDT Fri Aug 20 2021

...A strong thunderstorm will impact portions of northeastern
Huntingdon, central Mifflin and south central Centre Counties through
700 PM EDT...

At 632 PM EDT, Doppler radar was tracking a strong thunderstorm near
Boalsburg, moving southwest at 10 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Boalsburg, Belleville, Milroy, Strodes Mills, Reedsville, Whipple Dam
State Park, Mcalevys Fort, Potters Mills, Seven Mountains, Barrville
and Tussey Mountain Ski Area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4083 7773 4080 7753 4052 7767 4061 7794
TIME...MOT...LOC 2232Z 026DEG 7KT 4071 7772

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

Martin

Special Weather Statement
National Weather Service State College PA
709 PM EDT Fri Aug 20 2021

PAZ026-027-202345-
Huntingdon PA-Mifflin PA-
709 PM EDT Fri Aug 20 2021

...A strong thunderstorm will impact portions of northeastern
Huntingdon and southwestern Mifflin Counties through 745 PM EDT...

At 709 PM EDT, Doppler radar was tracking a strong thunderstorm over
Mcalevys Fort, moving southwest at 15 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Huntingdon, Mount Union, Belleville, Strodes Mills, Allensville,
Mcalevys Fort, Raystown Dam, Mapleton, McVeytown, Mill Creek,
Kistler, Atkinson Mills and Juniata College.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4068 7780 4057 7763 4035 7790 4053 7813
TIME...MOT...LOC 2309Z 047DEG 14KT 4060 7782

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

Martin