Alert archive / Pennsylvania / Flash Flood Warnings in 2019

Flash Flood Warning 90, NWS Pittsburgh, PA

July 21, 20194 counties in Pennsylvania

NWS Pittsburgh, PA issued this flash flood warning at Jul 21, 2019, 9:28 PM EDT for 4 counties in Pennsylvania. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 21, 2019, 9:28 PM EDT (01:28 UTC)
Expired: Jul 22, 2019, 12:30 AM EDT
In force: 3 hr
Issued by: NWS Pittsburgh, PA
Area: Storm-based polygon
Flood severity: None

Counties Allegheny County, PA, Fayette County, PA, Washington County, PA, Westmoreland County, PA

The radar

The Pittsburgh radar (KPBZ), 47 km from the middle of the area, began a volume at 01:29 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, 1.5 hours before the alert went out and 31 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 805 J/kg
Mixed-layer CIN: -57 J/kg
Mixed-layer LCL: 1290 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -5 m²/s²
0-3 km storm-relative helicity: 39 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood warning 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 flash flood warning went out at Jul 21, 6:29 PM EDT, 2 hours 59 minutes earlier.

Area forecast discussion, Jul 21, 6:29 PM EDT, 2 hours 59 minutes before

Area Forecast Discussion
National Weather Service Pittsburgh PA
629 PM EDT Sun Jul 21 2019

.SYNOPSIS...
The approach and passage of a cold front will bring rain throughout
the day Monday. Drier cooler weather can be expected for the
remainder of the week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
The eve update featured cosmetic POP adjustments based on radar and
high res model trends.

Previous...
Scattered and discontinuous convection continues along a very slow
moving and diffuse cold front stretching from approximately Coshocton
OH eastward towards Pittsburgh and into Westmoreland County PA. MLCAPE
values in the vicinity are in excess of 2500 J/kg for much of the
region. Combined with virtually no capping, storms should continue to
initiate along this boundary over the next few hours, despite little
in the way of upper forcing currently.

With steep low-level lapse rates and the presence of some mid-level
dry air, strong downdrafts / damaging wind gusts will be possible.
There is also a threat for localized flash flooding in urban or
other especially susceptible areas as storms train west to east
along the boundary.

Convective activity should initially wane a bit overnight as the
lower atmosphere stabilizes, though a few scattered showers are
still possible in close proximity to the frontal boundary.

Some convective-allowing models (CAMs) do suggest an uptick in
activity late overnight in association with some mid-level energy /
shortwave ahead of the main trough axis digging across the Ohio
Valley. Cloud cover and moist-low level air will keep temperatures
warm once again overnight. Lows will range from the mid 60s in the
vicinity of the I-80 corridor to mid 70s elsewhere.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
By Monday morning, storms will likely be ongoing along/near the
aforementioned frontal boundary. At this time, the cold front will
be stalled, bisecting the CWA. Exact placement is somewhat uncertain
and will ultimately depend on the convective evolution overnight
tonight.

Impressive shortwave trough will dig into the upper midwest Monday
evening and shift eastward overnight. This energy will push the
front southeastward, and it will reach the mid-atlantic region by
early Tuesday morning. Showers will end from NW to SE Monday night.
Cooler and much less humid air will spread across the region behind
the exiting rain.

Precipitation amounts on Monday will vary from from around half an
inch in places north of Pittsburgh to possibly in excess of an inch
along/south of the Mason-Dixon line and also in locations that see
multiple storms move across.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Cool, comparatively dry air will filter in behind the cold front on
Tuesday. A few lingering showers cannot be ruled out as cool air
moves over a warm Lake Erie, but otherwise most locales will be dry.
Cloud cover will gradually decrease through the day as high pressure
builds into the region.

Seasonal or even slightly below seasonal temperatures are expected
across the area through much of next week. Temperatures will rebound
by the weekend as southerly flow returns and high pressure slides
off the Atlantic coast. Ensembles and blended guidance are showing a
dry long term.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Brief MVFR/IFR restrictions are expected in any storm that passes
over a terminal with greatest confidence in the terminals between
I-70 and I-80 given latest hi res output.

Approaching shortwave trough will maintain shower chances, with
increasing coverage through Monday. Expect both ceiling and
visibility restrictions to continue until cold front crosses Monday
night.

.Outlook...
VFR will return behind the cold front passage, with prevailing VFR
expected for much of the week, outside of any morning fog.

&&

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

&&

Hazardous weather outlook, Jul 21, 2:15 AM EDT, 19 hours 13 minutes before

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
215 AM EDT Sun Jul 21 2019

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021-509>514-220615-
Garrett-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-Westmoreland Ridges-
Fayette-Fayette Ridges-Hancock-Brooke-Ohio-Marshall-Wetzel-Marion-
Monongalia-Ridges of Eastern Monongalia and Northwestern Preston-
Preston-Eastern Preston-Western Tucker-Eastern Tucker-
215 AM EDT Sun Jul 21 2019

This Hazardous Weather Outlook is for western Maryland, east
central Ohio, northwest Pennsylvania, southwest Pennsylvania, west
central Pennsylvania, western Pennsylvania, northern West Virginia
and northern panhandle of West Virginia.

.DAY ONE...Today and tonight.

Isolated severe storms are possible this afternoon and evening. The
main severe threat will be damaging wind gusts. Any storms will be
capable of producing heavy rain, increasing the threat for flooding.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

In the hours before

Local storm report, Jul 21, 7:45 PM EDT, 1 hour 43 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
745 PM EDT SUN JUL 21 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0744 PM     TSTM WND DMG     HOPWOOD                 39.88N  79.70W
07/21/2019                   FAYETTE            PA   COUNTY OFFICIAL

            NUMEROUS TREES DOWN. HOPWOOD AND UNIONTOWN.

&&

EVENT NUMBER PBZ1902759

15

Local storm report, Jul 21, 7:49 PM EDT, 1 hour 39 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
749 PM EDT SUN JUL 21 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0735 PM     FLASH FLOOD      HOPWOOD                 39.88N  79.70W
07/21/2019                   FAYETTE            PA   COUNTY OFFICIAL

            FLOODED ROADS AND BASEMENTS HOPWOOD

&&

EVENT NUMBER PBZ1902760

15

Local storm report, Jul 21, 7:50 PM EDT, 1 hour 38 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE PITTSBURGH PA
750 PM EDT SUN JUL 21 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0730 PM     TSTM WND DMG     HOPWOOD                 39.88N  79.70W
07/21/2019                   FAYETTE            PA   COUNTY OFFICIAL

            NUMEROUS TREES DOWN. HOPWOOD.

&&

CORRECTED EVENT TIME...REMARKS

EVENT NUMBER PBZ1902759

15

Local storm report, Jul 21, 8:04 PM EDT, 1 hour 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
804 PM EDT SUN JUL 21 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 PM     FLASH FLOOD      UNIONTOWN               39.90N  79.72W
07/21/2019                   FAYETTE            PA   COUNTY OFFICIAL

            NUMEROUS FLOODED ROADS

&&

EVENT NUMBER PBZ1902761

15

Local storm report, Jul 21, 8:22 PM EDT, 1 hour 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
822 PM EDT SUN JUL 21 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0435 PM     TSTM WND DMG     5 NE EAST BUTLER        40.93N  79.78W
07/21/2019                   BUTLER             PA   COUNTY OFFICIAL

            TREES DOWN RT. 68 IN OAKLAND TOWNSHIP

&&

EVENT NUMBER PBZ1902762

15

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 21, 8:41 PM EDT	Severe Thunderstorm Warning	PBZ	Allegheny, Beaver, Washington	34 min
Jul 21, 9:40 PM EDT	Flash Flood Warning	PBZ	Allegheny, Westmoreland	3 hr
Jul 21, 11:45 PM EDT	Areal Flood Advisory	PBZ	Clarion, Jefferson	3 hr
Jul 22, 12:15 AM EDT	Areal Flood Warning	PBZ	Allegheny, Westmoreland	12 hr
Jul 22, 12:52 AM EDT	Flash Flood Watch	PBZ	Allegheny, Beaver, Fayette, Greene, Washington, Westmoreland	19 hr
Jul 22, 12:13 PM EDT	Areal Flood Advisory	PBZ	Armstrong, Butler, Indiana, Jefferson	3 hr
Jul 22, 1:04 PM EDT	Flash Flood Warning	PBZ	Allegheny, Westmoreland	3 hr
Jul 22, 1:38 PM EDT	Areal Flood Advisory	PBZ	Washington	2 hr
Jul 22, 3:49 PM EDT	Areal Flood Advisory	PBZ	Fayette	116 min
Jul 22, 1:48 AM EDT	Areal Flood Advisory	PBZ	Muskingum	2 hr
Jul 22, 2:29 AM EDT	Flash Flood Warning	PBZ	Muskingum	66 min
Jul 22, 4:37 PM EDT	Areal Flood Advisory	PBZ	Monongalia	113 min
Jul 22, 5:15 PM EDT	Areal Flood Advisory	PBZ	Marion	2 hr

Nearby

Flash Flood Warnings in Pennsylvania, 2019 Every flash flood warning in 2019

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.