Alert archive / Pennsylvania / Special Weather Statements in 2021

Special Weather Statement, NWS Pittsburgh, PA

July 20, 2021Armstrong County, Pennsylvania

NWS Pittsburgh, PA issued this special weather statement at Jul 20, 2021, 9:39 PM EDT for Armstrong County, Pennsylvania. It was in force for 36 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Jul 20, 2021, 9:39 PM EDT (01:39 UTC)
Expired
Jul 20, 2021, 10:15 PM EDT
In force
36 min
Issued by
NWS Pittsburgh, PA

County Armstrong County, PA

The radar

The Pittsburgh radar (KPBZ), 78 km from the middle of the area, began a volume at 01:42 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Pittsburgh, PA (KPIT), launched 00:00Z, 1.7 hours before the alert went out and 77 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Pittsburgh, PA at 00:00Z on 2021-07-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 416 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Pittsburgh, PA at 00:00Z on 2021-07-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 22 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
416 J/kg
Mixed-layer CIN
-16 J/kg
Mixed-layer LCL
1443 m above ground
0-6 km bulk shear
21 kt
0-1 km storm-relative helicity
22 m²/s²
0-3 km storm-relative helicity
33 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Pittsburgh, PA wrote its last area forecast discussion before this special weather statement went out at Jul 20, 7:19 PM EDT, 2 hours 20 minutes earlier.

Area forecast discussion, Jul 20, 7:19 PM EDT, 2 hours 20 minutes before
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
719 PM EDT Tue Jul 20 2021

.SYNOPSIS...
A crossing cold front will bring the risk for showers and
thunderstorms overnight and into Wednesday morning. Dry weather
should return Thursday under high pressure.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Broken line of showers and thunderstorms has developed over the I-80
corridor. The main threat from these storms is heavy downpours and
large hail. The lack of strong shear is prohibiting the development
of long duration strong updrafts, but the storms are reaping the
benefits of short lived updrafts that are likely getting an assist
from outflows of the collapsing ones. This activity has developed
ahead of a surface boundary which got a boost from the lake breeze.
South of this line, activity is much weaker and very isolated. Expect
the activity to weaken during the evening hours as it moves further
away from the lake and the sun sets.

Will need to keep in the mention of showers and thunderstorms
overnight as the boundary crosses the region and receives an assist
from a crossing shortwave.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Isolated to scattered showers will wane as the morning and system
progress on Wednesday. Cooler and less humid conditions are
expected behind the front as high pressure builds through Thursday
under NW flow aloft.

An approaching shortwave trough in the NW flow should result in low
chances for showers Thursday night, mainly N of PIT.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Model ensembles indicate troughing should persist across much of the
Eastern CONUS through the period. Occasional shower and thunderstorm
chances are expected as shortwaves embedded in NW flow aloft cross
the region, though significant timing/location differences exist in
the operational models. Stayed close to the blended ensemble guidance
to smooth out some of these differences.

&&

.AVIATION /23Z TUESDAY THROUGH SUNDAY/...
A shortwave trough, in nw flow, and its associated sfc cold front,
will move across the region overnight. Included tsra at FKl and DUJ
as scattered showers/tstms move across the region with the
approaching front. Cig deterioration to MVFR and IFR is then expected
after FROPA late tonight for ports near and N of PIT. Restrictions
are possible through erly Wed with the crossing cold front.

.Outlook...
The next restriction chc is expected Fri and Sat with crossing
fronts.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&
Hazardous weather outlook, Jul 20, 3:19 AM EDT, 18 hours 20 minutes before
Hazardous Weather Outlook
National Weather Service Pittsburgh PA
319 AM EDT Tue Jul 20 2021

OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-029-
031-073>076-WVZ001>004-012-021-509>514-210730-
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH-
Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest-
Lawrence-Butler-Clarion-Jefferson PA-Beaver-Allegheny-Armstrong-
Indiana-Washington-Greene-Westmoreland-
Higher Elevations of Westmoreland-Fayette-
Higher Elevations of Fayette-Hancock-Brooke-Ohio-Marshall-Wetzel-
Marion-Monongalia-
Ridges of Eastern Monongalia and Northwestern Preston-Preston-
Eastern Preston-Western Tucker-Eastern Tucker-
319 AM EDT Tue Jul 20 2021

This Hazardous Weather Outlook is for east central Ohio, western
Pennsylvania, and northern West Virginia.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

In the hours before

Special weather statement, Jul 20, 9:11 PM EDT, 28 minutes before
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Special weather statement, Jul 20, 9:16 PM EDT, 23 minutes before
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Local storm report, Jul 20, 9:25 PM EDT, 14 minutes before
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Local storm report, Jul 20, 9:33 PM EDT, 6 minutes before
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Special weather statement, Jul 20, 9:38 PM EDT, 1 minute before
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Special weather statement, Jul 20, 9:39 PM EDT, 0 minutes before
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The office that day

Everything else NWS Pittsburgh, PA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 20, 8:31 PM EDTSpecial Weather StatementPBZBeaver29 min
Jul 20, 8:32 PM EDTSevere Thunderstorm WarningPBZArmstrong, Clarion, Forest, Indiana, Jefferson43 min
Jul 20, 8:45 PM EDTSevere Thunderstorm WarningPBZAllegheny, Beaver, Butler30 min
Jul 20, 9:11 PM EDTSpecial Weather StatementPBZButler34 min
Jul 20, 9:16 PM EDTSpecial Weather StatementPBZArmstrong29 min
Jul 20, 8:01 PM EDTSpecial Weather StatementPBZHancock29 min
Jul 20, 9:09 PM EDTSpecial Weather StatementPBZBrooke36 min
Jul 20, 9:38 PM EDTSpecial Weather StatementPBZBrooke37 min
Jul 21, 4:44 AM EDTSpecial Weather StatementPBZMarion, Monongalia, Preston46 min
Jul 20, 8:20 PM EDTSpecial Weather StatementPBZColumbiana25 min

Nearby

Special Weather Statements in Pennsylvania, 2021Every special weather statement in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.