Alert archive / Pennsylvania / Flash Flood Watches in 2021

Flash Flood Watch 7, NWS State College, PA

August 27, 20214 counties in Pennsylvania

NWS State College, PA issued this flash flood watch at Aug 27, 2021, 4:40 AM EDT for 4 counties in Pennsylvania. It took effect at Aug 27, 2021, 1:00 PM EDT. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued
Aug 27, 2021, 4:40 AM EDT (08:40 UTC)
In effect from
Aug 27, 2021, 1:00 PM EDT
Expired
Aug 27, 2021, 9:28 PM EDT
In force
8 hr
Issued by
NWS State College, PA
Flood severity
None

Counties Dauphin County, PA, Lancaster County, PA, Lebanon County, PA, York County, PA

The radar

The State College radar (KCCX), 147 km from the middle of the area, began a volume at 08:41 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 8.7 hours before the alert went out and 155 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, Washington/Dulle, VA at 00:00Z on 2021-08-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1253 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 2021-08-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 13 square meters per square second.1939Sfc1 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
1253 J/kg
Mixed-layer CIN
-53 J/kg
Mixed-layer LCL
1438 m above ground
0-6 km bulk shear
8 kt
0-1 km storm-relative helicity
13 m²/s²
0-3 km storm-relative helicity
37 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

076 
WGUS61 KCTP 270840
FFACTP

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service State College PA
440 AM EDT Fri Aug 27 2021

PAZ057-059-065-066-272345-
/O.NEW.KCTP.FF.A.0007.210827T1700Z-210828T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Dauphin-Lebanon-York-Lancaster-
Including the cities of Lancaster, Harrisburg, Lebanon, Hershey, and 
York
440 AM EDT Fri Aug 27 2021

...FLASH FLOOD WATCH IN EFFECT FROM 1 PM EDT THIS AFTERNOON THROUGH 
LATE TONIGHT...

The National Weather Service in State College has issued a

* Flash Flood Watch for a portion of central Pennsylvania, including 
  the following areas, Dauphin, Lancaster, Lebanon and York.

* From 1 PM EDT this afternoon through late tonight.

* The potential for localized, heavy downpours over a short duration 
  along with elevated streamflows, above normal soil moisture, and 
  above average rainfall in the past week will result in an 
  increased risk of isolated to scattered rapid-onset flooding.

* Urban areas are the most vulnerable with street flooding and road 
  closures possible. Rapid rises on streams and creeks may occur and 
  could lead to adjacent inundation flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

Steinbugl/Martin
3 follow-up statements
494 
WGUS61 KCTP 271828
FFACTP

Flood Watch
National Weather Service State College PA
228 PM EDT Fri Aug 27 2021

PAZ057-059-065-066-280500-
/O.CON.KCTP.FF.A.0007.000000T0000Z-210828T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Dauphin-Lebanon-York-Lancaster-
Including the cities of Harrisburg, Hershey, Lebanon, York, 
and Lancaster
228 PM EDT Fri Aug 27 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 1 AM EDT SATURDAY...

The Flash Flood Watch continues for

* A portion of central Pennsylvania, including the following 
  areas, Dauphin, Lancaster, Lebanon, and York. 

* Until 1 AM EDT Saturday

* The potential for localized, heavy downpours over a short 
  duration along with elevated streamflows, above normal soil 
  moisture, and above average rainfall in the past week will 
  result in an increased risk of isolated to scattered rapid- 
  onset flooding. 

* Urban areas are the most vulnerable with street flooding and 
  road closures possible. Rapid rises on streams and creeks may 
  occur and could lead to adjacent inundation flooding. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

&&

$$
476 
WGUS61 KCTP 280013
FFACTP

Flood Watch
National Weather Service State College PA
813 PM EDT Fri Aug 27 2021

PAZ057-065-280115-
/O.CAN.KCTP.FF.A.0007.000000T0000Z-210828T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Dauphin-York-
Including the cities of Harrisburg, Hershey, and York
813 PM EDT Fri Aug 27 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch for a portion of central Pennsylvania, 
including  Dauphin and York counties, has been cancelled.

The Flood Watch is cancelled.

$$

PAZ059-066-280500-
/O.CON.KCTP.FF.A.0007.000000T0000Z-210828T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lebanon-Lancaster-
Including the cities of Lancaster and Lebanon
813 PM EDT Fri Aug 27 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 1 AM EDT SATURDAY...

The Flash Flood Watch continues for

* A portion of central Pennsylvania, including the following areas, 
  Lancaster and Lebanon.

* Until 1 AM EDT Saturday.

* Heavy showers and thunderstorm have diminished in intensity this 
  evening. However, isolated flooding still can't be rule out 
  through late evening.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

KF
067 
WGUS61 KCTP 280128
FFACTP

Flood Watch
National Weather Service State College PA
928 PM EDT Fri Aug 27 2021

PAZ059-066-280230-
/O.CAN.KCTP.FF.A.0007.000000T0000Z-210828T0500Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lebanon-Lancaster-
Including the cities of Lancaster and Lebanon
928 PM EDT Fri Aug 27 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch for a portion of central Pennsylvania, 
including  Lancaster and Lebanon counties, has been cancelled.

The Flood Watch is cancelled. Flooding is no longer expected to pose 
a threat. Please continue to heed remaining road closures.

$$

KF

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 27, 2:13 PM EDTAreal Flood AdvisoryCTPPotter2 hr
Aug 27, 3:10 PM EDTSpecial Weather StatementCTPYork35 min
Aug 27, 3:37 PM EDTSpecial Weather StatementCTPJuniata38 min
Aug 27, 4:13 PM EDTSpecial Weather StatementCTPTioga32 min
Aug 27, 4:29 PM EDTAreal Flood AdvisoryCTPTioga2 hr
Aug 27, 4:34 PM EDTAreal Flood AdvisoryCTPColumbia, Northumberland, Schuylkill2 hr
Aug 27, 4:50 PM EDTAreal Flood AdvisoryCTPLancaster, York115 min
Aug 27, 4:55 PM EDTFlash Flood Warning Considerable damage threatCTPTioga99 min
Aug 27, 5:02 PM EDTSpecial Weather StatementCTPYork28 min
Aug 27, 5:11 PM EDTSpecial Weather StatementCTPLancaster49 min
Aug 27, 5:13 PM EDTSpecial Weather StatementCTPDauphin47 min
Aug 27, 5:16 PM EDTSevere Thunderstorm WarningCTPLancaster59 min
Aug 27, 5:38 PM EDTAreal Flood AdvisoryCTPDauphin, Lebanon2 hr
Aug 27, 5:46 PM EDTAreal Flood AdvisoryCTPLancaster, Lebanon80 min
Aug 27, 5:57 PM EDTFlash Flood Warning Considerable damage threatCTPDauphin70 min
Aug 27, 6:05 PM EDTSpecial Weather StatementCTPLebanon25 min
Aug 27, 6:07 PM EDTFlash Flood Warning Considerable damage threatCTPLancaster60 min
Aug 27, 6:18 PM EDTAreal Flood AdvisoryCTPDauphin, Lebanon, Schuylkill2 hr

Nearby

Flash Flood Watches in Pennsylvania, 2021Every flash flood watch 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.