Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 031853
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 PM EDT FRI JUL 03 2015

...VALID 1852Z FRI JUL 03 2015 - 12Z SAT JUL 04 2015...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 S GLH 25 E BQP 20 NNW DTN 10 WNW TKI 25 ESE SPS 20 SSW CHK
10 S FYV 10 NW MKL 30 WNW CSV 20 NW JKL 20 SW PKB AGC 15 S FIG
15 SW UNV 15 ESE CBE W99 35 WNW SHD 20 SSW HSP PSK 15 SW HLX UKF
10 SW EHO 10 NW IIY 30 S WDR 35 NW CCO 25 ESE GTR 40 S GLH.



...SOUTHERN PLAINS/LOWER MS VALLEY/OH VALLEY/TN VALLEY...

MOISTURE AND INSTABILITY WILL INTERACT WITH SHORT WAVES IN THE MID
LEVEL FLOW TO PRODUCE CONVECTIVE CLUSTERS ALONG AND SOUTH OF A
QUASI STATIONARY FRONT EXTENDING FROM THE LOWER AND MID MS VALLEY
ACROSS THE TN VALLEY INTO THE SOUTHEAST STATES. GIVEN THE HIGH
MOISTURE CONTENT OF THE AIR IN THE PRESENCE OF THE MID LEVEL
SYNOPTIC SCALE ASCENT...FLASH FLOODING POSSIBLE ACROSS THIS
REGION.

CONVECTIVE CLUSTERS TRACKING ALONG AND SOUTH OF THE FRONT FROM
EASTERN OK ACROSS NORTHERN MS/AL/GA ARE PRODUCING VERY HEAVY
RAINFALL AND FLASH FLOODING. THE STORMS LIE IN AN AXIS OF 2.00+
INCH PRECIPITABLE WATER...AND AS A SHORT WAVE OVER WESTERN KY/TN
TRACKS EAST NORTHEAST...IT WILL PROVIDE ADDITIONAL LIFT FOR
CONVECTIVE CLUSTERS THROUGH AT LEAST 4/00Z. HIGH RAINFALL RATES
AND TRAINING SHOULD RESULT IN ADDITIONAL FLASH FLOODING ASSOCIATED
WITH THE SHORT WAVE...AND THERE IS MULTI MODEL HIGH RESOLUTION
MODEL SUPPORT FOR THIS.

THE AXIS OF HEAVIEST RAINFALL DRIFTS SOUTH DURING THE EVENING AND
EARLY OVERNIGHT.  THE BEST INSTABILITY REMAINS SOUTH OF THE
BOUNDARY...AND THE COMBINATION OF THE FRONT SLOWLY SAGGING SOUTH
AND OUTFLOW BOUNDARIES PUSHING SOUTH SHOULD RESULT IN THE AXIS OF
HEAVIEST QPF EXTENDING FROM THE LOWER MS VALLEY ACROSS NORTHERN
AND CENTRAL MS/NORTHERN AL INTO PORTIONS OF NORTHWEST GA/EASTERN
TN. THE THREAST FOR FLASH FLOODING CONTINUES DROP SOUTH INTO THIS
AREA. A SLIGHT RISK WAS EXTENDED A BIT FURTHER SOUTH TO COVER
THESE AREAS.

A SECOND SHORT WAVE TRACKING ACROSS KS/MO LATE THIS AFTERNOON
CROSSES THE OH VALLEY INTO THE MID ATLANTIC BETWEEN
4/06Z-4/12Z...WHICH SPINS UP A SURFACE WAVE OVER NORTHERN WV
AROUND 4/06Z. THE 20 TO 30 KNOT LOW LEVEL FLOW BACKS AHEAD OF A
DEVELOPING WARM FRONT...ALLOWING 1.75 INCH PRECIPITABLE WATER TO
RIDE UP AND OVER THE WARM FRONT. MODEL SOUNDINGS SHOWED MARGINAL
INSTABILITY AND A MOISTENING COLUMN...SUGGESTING WARM RAIN
PROCESSES BECOME MORE IMPORTANT WITH TIME. THE COMBINATION OF HIGH
RAINFALL RATES AND VERY LOW ONE AND THREE HOUR FLASH FLOOD
GUIDANCE (AS LOW AS AN INCH ACROSS PORTIONS OF EASTERN TN/EASTERN
KY/WV/WEST CENTRAL PA) SUGGESTED AN ENHANCED THREAT FOR FLASH
FLOODING DURING THE BEST SYNOPTIC SCALE ASCENT. FOR THIS
REASON...THE SLIGHT RISK AREA WAS EXTENDED ACROSS MUCH OF THE
ABOVEMENTIONED AREAS.


...SOUTHWEST...

MONSOONAL MOISTURE COMBINING WITH MARGINAL TO MODERATE INSTABILITY
COULD LEAD TO ISOLATED FLASH FLOODING ACROSS PORTIONS OF THE
SOUTHWEST STATES...MAINLY AFTER 4/00Z. A LOW LEVEL EAST SOUTHEAST
FROM FROM THE SOUTHERN PLAINS TRANSPORTS 1.25 PRECIPITABLE WATER
AIR IN NM...WHILE THE MONSOONAL FLOW BRINGS 1.75 INCH PRECIPITABLE
WATER AIR IN SOUTHERN AZ. MODEL SOUNDINGS SHOWED MARGINAL TO
LOCALLY MODERATE INSTABILITY...
WHICH APPEARS TO PEAK AFTER 4/00Z ACROSS SOUTHEAST AZ/SOUTHWEST
NM. WEAK SHORT WAVES IN THE MID LEVEL EASTERLY FLOW COULD PROVIDE
LOCAL SYNOPTIC LIFT FOR CONVECTIVE DEVELOPMENT THROUGH 4/00Z.

THERE IS A MULTI MODEL SIGNAL THAT A WEAK SHORT WAVE RUNNING
WESTWARD AT THE BOTTOM OF THE WESTERN UNITED STATES RIDGE COULD
SPARK AN MCS ACROSS NM/AZ. NAM SIMULATED SATELLITE IMAGERY
SUGGESTS AN MCS WILL FORM OVER WEST CENTRAL NM/EAST CENTRAL AZ
AFTER 4/02Z...WHICH TRACKS WESTWARD ACROSS AZ THROUGH 4/09Z. WHILE
MOST MODEL QPF OUTPUT ACROSS THIS AREA IS GENERALLY UNDER AN
INCH...THE HIGH MOISTURE CONTENT OF THE AIR COULD RESULT IN HIGHER
RAINFALL RATES WITH THE MCS. GIVEN THAT THE ONE HOUR FLASH FLOOD
GUIDANCE IS MOSTLY LESS THAN 1.50 INCHES ACROSS NM/AZ...A SEE TEXT
AREA HAS BEEN INTRODUCED.


...NORTHERN CA/NORTHERN NV...

PRECIPITABLE WATER VALUES VALUES TOPPING OUT NEAR 1.25 INCHES
(WHICH IS BETWEEN THREE AND FOUR STANDARD DEVIATIONS ABOVE THE
MEAN) WILL FUEL SCATTERED CONVECTION DEVELOPING IN AN AREA OF
DIFFLUENCE AND MID LEVEL DRYING. THE CONVECTION PROBABLY REMAINS
FAIRLY SCATTERED THROUGH THE AFTERNOON AND EVENING
HOURS...ESPECIALLY OVER THE SIERRA NEVADA RANGE THROUGH NORTHERN
NV. WHILE BASIN AVERAGE QPF SHOULD RANGE BETWEEN 0.25 TO 0.50
INCHES...LOCAL AMOUNTS COULD EASILY EXCEED AN INCH OR
MORE...PARTICULARLY WHERE TRAINING OCCURS IN THE MID LEVEL SOUTH
SOUTHEAST FLOW.

HAYES
$$




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