WPC Excessive Rainfall Outlook Day 1
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 Excessive Rainfall Forecast Discussion
Excessive Rainfall Discussion

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FOUS30 KWBC 231503
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1003 AM EST THU NOV 23 2017

...VALID 15Z THU NOV 23 2017 - 12Z FRI NOV 24 2017...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


MARGINAL RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
85 ENE TTS TIX LAL 20 NW PIE 35 S CTY 25 NNE CTY 35 NE NRB
130 SE HXD.


1500 UTC UPDATE

NO CHANGES MADE TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL
OUTLOOK.

ORAVEC


INITIAL DISCUSSION

...FLORIDA...

A MID/UPPER LEVEL TROUGH WILL CONTINUE TO PUSH ACROSS THE EASTERN
U.S....WITH THE BASE OF THE TROUGH MOVING ACROSS THE GULF OF
MEXICO AND ACROSS FL. ONE OR MORE WEAK SURFACE LOW REFLECTIONS
WILL ALSO PUSH EAST NEAR FL THROUGH THE PERIOD. WILL SEE
INCREASING UPPER LEVEL DIVERGENCE...AS A STRENGTHENING JET TO THE
NORTH PUTS FL IN THE FAVORED RIGHT ENTRANCE REGION. PWAT VALUES
ACROSS FL SHOULD CONTINUE TO INCREASE TO AROUND THE CLIMATOLOGICAL
90TH PERCENTILE TODAY. THUS DO HAVE SOME PARAMETERS IN PLACE FOR
POTENTIAL HEAVY RAINFALL.

CLOSER TO THE SURFACE SHOULD HAVE A BOUNDARY SET UP ACROSS NORTH
CENTRAL FL...WITH MORE STABLE OVERRUNNING RAINFALL TO THE NORTH OF
THIS BOUNDARY...AND MORE CONVECTIVE RAINFALL TO ITS SOUTH. LACK A
FOCUS MECHANISM WELL SOUTH OF THE BOUNDARY...SO WHILE WE SHOULD
SEE ISOLATED CONVECTION ACROSS CENTRAL AND SOUTH FL...AREAL
COVERAGE OF HIGHER AMOUNTS SHOULD STAY LOW. THE BEST CHANCE FOR A
MORE FOCUSED AXIS OF HIGHER AMOUNTS SHOULD END UP RIGHT NEAR THE
AFOREMENTIONED BOUNDARY...WHERE WE HAVE BETTER CONVERGENCE AND
JUST ENOUGH INSTABILITY FOR EMBEDDED HEAVIER CONVECTIVE ELEMENTS.
WIDESPREAD 1-3" OF RAIN IS EXPECTED HERE...WITH MORE ISOLATED
POCKETS OF 3-6" POSSIBLE.

GIVEN THE DRY ANTECEDENT CONDITIONS AND HIGH FLASH FLOOD GUIDANCE
OVER THE AREA...DO NOT THINK RAINFALL RATES OR TOTALS WILL BE HIGH
ENOUGH FOR AN ORGANIZED FLASH FLOOD THREAT. HOWEVER ISOLATED
ISSUES COULD ARISE WHERE CELL MERGERS LOCALLY PUSH AMOUNTS INTO
THE 3-6" RANGE...AND OVER ANY MORE URBANIZED LOCATIONS. THUS WILL
MAINTAIN THE MARGINAL RISK OVER NORTH CENTRAL FL. SOME UNCERTAINTY
ON THE EXACT AXIS OF HIGHEST AMOUNTS...BUT BASED ON RECENT RADAR
AND SATELLITE TRENDS...ALONG WITH THE LOCATION OF
INSTABILITY...FAVORED A SLIGHTLY FURTHER SOUTH SOLUTION CLOSER TO
THE 0Z HRW ARW AND 03Z HRRR EXPERIMENTAL.

CHENARD


$$

Record Report from: NOAA-NWS
Script developed by: El Dorado Weather & modified by: SE Lincoln Weather