National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FOUS30 KWBC 231419
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1019 AM EDT THU MAY 23 2013

...VALID 15Z THU MAY 23 2013 - 12Z FRI MAY 24 2013...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...



UPDATE


ACROSS CENTRAL OK---TRAINING OF CELLS IN A NORTHWEST TO
SOUTHEASTERLY DIRECTION POSSIBLE OVER THE NEXT FEW HOURS IN THE
VICINITY OF THE OKC AREA.  THE LEAD AREA OF CONVECTION THAT
AFFECTED THIS AREA EARLIER THIS MORNING HAS BECOME INCREASINGLY
PROGRESSIVE WITH RUNOFF ISSUES HAVING DIMINISHED WITH THIS LEAD
AREA.  ADDITIONAL CONVECTION HAS FORMED ON THE NORTHWEST SIDE OF
THE COMPLEX--WITH TRAINING OF CELLS OVER THE NEXT FEW HOURS
CONTINUING TO PRODUCE ISOLATED SHORT TERM PRECIPITATION AMOUNTS OF
1-2".  THE LOW LEVEL SOUTHWESTERLY FLOW THAT HAS OVERRUN THE FRONT
ACROSS NORTH TX IS EXPECTED TO BACK TO A MORE EAST SOUTHEASTERLY
DIRECTION THIS AFTERNOON.  THIS SHOULD FAVOR DECREASED OVERRUNNING
CONVECTION OVER OK---WITH ACTIVITY FORMING FARTHER TO THE
SOUTHWEST OVER SOUTHWEST OK AND NORTH TX.

THE ONLY CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL
OUTLOOK OVER THE EASTERN U.S. WAS TO ALSO EMPHASIZE THE CENTRAL
APPALACHIAN REGION  FOR POTENTIAL RUNOFF ISSUES.  WITH FFG VALUES
AS LOW AS .50-.75" FOR 1 HOUR AND .75-1"+ FOR THE 3 HOUR PERIOD
OVER PORTIONS OF THE NORTHWESTERN VA/EASTERN WV BORDER AREA AND
FARTHER WESTWARD ACROSS WV---THERE MAY BE LOCALIZED RUNOFF ISSUES
WITH THE POTENTIAL FOR INCREASING CONVECTIVE ACTIVITY THIS
AFTERNOON IN THE AXIS OF ABOVE AVERAGE PW VALUES ALONG AND AHEAD
OF THE LEAD FRONTAL BOUNDARY FORECAST TO PUSH EASTWARD.

NO CHANGES IN THINKING WITH RUNOFF ISSUE POTENTIAL FARTHER
NORTHWARD FROM PORTIONS OF UPSTATE NY INTO NEW ENGLAND.


ORAVEC



PREVIOUS DISCUSSION

...NORTHERN MID ATLANTIC STATES INTO INTERIOR NEW ENGLAND...

IT SHOULD BE A WET PERIOD FOR THE NORTHEASTERN STATES THIS
PERIOD..AHEAD OF AN H5 TROF DIGGING INTO THE EASTERN STATES WITH
THE MID LEVEL FLOW BACKING RATHER SIGNIFICANTLY INTO THE REGION BY
FRIDAY MORNING.  THIS BACKING MID LEVEL FLOW AND A CONTINUED
SOUTH-SOUTHWESTERLY LOW LEVEL FLOW UP THRU THE MID ATLANTIC AND
NORTHEASTERN STATES WILL BRING IN AN AXIS OF MUCH ABOVE AVERAGE PW
VALUES..AT OR ABOVE 1.50 INCHES..ALONG AND AHEAD OF THE
ACCOMPANYING COLD FRONT.  THIS HIGH MOISTURE ALONG WITH RATHER
DECENT BOUNDARY LAYER CONVERGENCE AND FAVORABLE RIGHT ENTRANCE
REGION UPPER JET DYNAMICS SHOULD SUPPORT THE WIDESPREAD MODERATE
TO HEAVY RAINFALL EVENT..ESPECIALLY FROM THE NORTHERN MID ATLANTIC
STATES INTO INTERIOR NEW ENGLAND.
THE MODEL QPFS GENERALLY FAVOR FAIRLY WIDESPREAD 0.50-1.00+ INCH
RAINFALL TOTALS..BUT WITH SOME AMOUNTS APPROACHING 2 INCHES NOT
OUT OF THE QUESTION FROM NORTHEASTERN PA NORTHEASTWARD INTO
WESTERN ME WHERE THE EVENT WILL PERSIST EVEN BEYOND THIS PERIOD.

TERRY

$$