Quantitative Precipitation Forecast
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FOUS30 KWBC 280033
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
833 PM EDT MON MAR 27 2017

...VALID 01Z TUE MAR 28 2017 - 12Z TUE MAR 28 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 S LEX 45 ESE LUK 45 W UNI 3I2 20 E HTS 30 E JKL 15 E 1A6
30 NNE 1A5 20 NNW GVL BHM 25 W 1M4 40 NNE TUP 30 NNE MSL
20 ESE MQY 20 W EKQ 25 S LEX.


...EASTERN U.S. CONVECTIVE ENVIRONMENT FROM OHIO TO ALABAMA TO
SOUTHWEST VIRGINIA...

STEEP LAPSE RATES...BROAD MOISTURE TRANSPORT...AND MODERATELY
STRONG HEIGHT FALLS AHEAD OF A SHARP SHORTWAVE TROUGH WILL SUPPORT
WIDESPREAD CONVECTION THROUGH THE LATE EVENING HOURS. BY 00Z
CLUSTERS OF STORMS IN THE PRE-FRONTAL ENVIRONMENT HAD
CONSOLIDATED...SHARING A COMMON ANVIL AND TRAILING STRATIFORM
REGION FROM SOUTHERN IN/OH TO NORTHERN AL/GA. STILL...WITH STRONG
SHEAR AND MODERATE INSTABILITY IN PLACE...CONVECTIVE MODES WERE
STILL MIXED...WITH A FEW SUPERCELLS OCCURRING. BEHIND ALL OF THIS
ACTIVITY...AND CLOSER TO THE CORE OF THE MID LEVEL TROUGH AND
ADVANCING SURFACE COLD FRONT...WAS A SECOND ORGANIZED MCS ACROSS
CENTRAL AND WESTERN TENNESSEE.  THIS WILL ALSO BE SUPPORTED BY THE
BROAD SOUTHWESTERLY FLOW LEVEL FLOW...RESULTING IN BOTH THE
POTENTIAL FOR SHORT TERM WEST TO EAST TRAINING OF CELLS...AND A
MULTI-HOUR ACCUMULATION OF HEAVY RAIN OWING TO THE PASSAGE OF BOTH
CONVECTIVE SYSTEMS...MAINLY OVER SOUTHERN TENNESSEE AND ADJACENT
NORTHER ALABAMA AND GEORGIA.

FLASH FLOOD GUIDANCE IN THIS REGION IS GENERALLY 1.5 INCHES IN ONE
HOUR OR 2 TO 2-PLUS INCHES IN 3 HOURS. THE THREE-HOUR CRITERIA IS
A BIT MORE LIKELY TO BE EXCEEDED ON A LOCAL BASIS...AS MARGINAL PW
VALUES AROUND 1.00 INCH AND SOME HAIL FALL WILL LIMIT THE
EFFECTIVENESS OF HOURLY RAIN RATES...EXCEPT WHERE MERGERS OCCUR.
ISOLATED TOTALS OF 2.5 INCHES CAN BE EXPECTED.

BURKE
$$





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