Quantitative Precipitation Forecast
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FOUS30 KWBC 291857
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT MON SEP 29 2014

...VALID 18Z MON SEP 29 2014 - 00Z WED OCT 01 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 ENE PBI 30 WSW PBI 35 SSE BOW 30 W CTY 15 W VAD 20 SW TBR
30 ESE OGB 30 SSW MYR 65 ESE CHS 45 ENE SSI 25 ENE DAB
35 ENE VRB 20 ENE PBI.


...CENTRAL/NORTHERN HIGH PLAINS...

THE CLOSED MID/UPPER LEVEL LOW CURRENTLY ACROSS THE GREAT BASIN
WILL FINALLY LIFT E THEN NE INTO THE NORTHERN PLAINS BY THE END OF
THE PERIOD AS ANOTHER SHORTWAVE TROUGH AND ASSOCIATED UPPER JET
STREAK DROPS INTO THE PAC NW AND NORTHERN INTERMOUNTAIN WEST.
THESE TROUGHS WILL EVENTUALLY PHASE...THOUGH NOT DURING THE DAY 1
PERIOD (THROUGH 00Z WED)...HOWEVER THE APPROACHING UPSTREAM JET
AXIS/SHORTWAVE TROUGH WILL CAUSE THE LEAD TROUGH TO TAKE ON A
NEGATIVE TILT UPON LIFTING OUT INTO THE CENTRAL/NORTHERN PLAINS ON
TUESDAY. STRENGTHENING DYNAMICAL SUPPORT WILL SPREAD INTO THE
FOOTHILLS AND EVENTUALLY CEN/NRN PLAINS DURING THE PERIOD...WITH
THE INCREASINGLY NEGATIVE TILT TO THE TROUGH LEADING TO STRONGER
UPPER LEVEL DIFFLUENCE/DIVERGENCE AND DEEP LAYER QVECTOR
CONVERGENCE. THE MODELS AGAIN SHOW THE UPPER DIVERGENCE MAXIMIZING
OVERNIGHT OVER THE WY/NORTHERN CO FOOTHILLS AND INTO THE NORTHERN
HIGH PLAINS...AS AN UPPER LEVEL JET STREAK ROUNDS THE TROUGH BASE
(ENHANCED LEFT EXIT REGION FORCING AND MORE ROBUST DEEP-LAYER
ASCENT). AT LOW LEVELS...THE PRE-TROUGH THERMODYNAMIC ENVIRONMENT
BECOMES INCREASINGLY FAVORABLE GIVEN THE INCREASING S-SE LOW-LEVEL
AGEOSTROPHIC RESPONSE...THOUGH THE AXIS OF HIGHEST PWS (ABOVE 1.25
INCHES) ALONG A 40-50 KT LOW LEVEL JET SHIFTS FARTHER EAST ACROSS
THE CEN/NRN PLAINS WHILE BECOMING MORE DISPLACED WITH THE BEST
UVVS/UPPER DIVERGENCE OVER THE FOOTHILLS AND HIGH PLAINS. AS A
RESULT...MODEL PROJECTED MUCAPES WITHIN THE AXIS OF BEST DYNAMICAL
FORCING (AND ANOMALOUS EASTERLY/UPSLOPE LOW-LEVEL FLOW) ARE
GENERALLY BELOW 500 J/KG...THEREFORE THE EXCESSIVE RAINFALL
POTENTIAL (SHORT TERM RAINFALL RATES) WILL BE LIMITED. AT THE SAME
TIME...THE AFOREMENTIONED ANOMALOUS EASTERLY COMPONENT (NEGATIVE
850 MB U WIND COMPONENT BTWN 4-5 STANDARD DEVIATIONS) ACROSS THE
WY/NORTHERN CO FOOTHILLS AND NORTHERN HIGH PLAINS WILL AGAIN FAVOR
MAXIMUM TERRAIN- ENHANCED RAINFALL TOTALS (AREAL-AVERAGE AMOUNTS
BETWEEN 1-3 INCHES)...EVEN THOUGH THE EXCESSIVE RAINFALL POTENTIAL
WILL BE MITIGATED BY THE LACK (ABSENCE) OF DEEP LAYER INSTABILITY.


...SOUTHEASTERN STATES...

EXPECT AREAS OF MODERATE TO HEAVY RAINFALL TO CONTINUE INTO THE
EVENING HOURS OVER THIS REGION AS THE UPPER TROUGH -- CURRENTLY
PUSHING THROUGH THE TN VALLEY -- CONTINUES TO PRESS EASTWARD.
ANOTHER 3-6 HOURS OF FAVORABLE DYNAMICAL SUPPORT (UPPER LEVEL
DIVERGENCE AND MORE FOCUSED SOUTHERLY LOW-LEVEL MOISTURE
CONVERGENCE) AHEAD OF THE SHORTWAVE TROUGH WILL MAINTAIN THE
WIDESPREAD WARM-TOPPED CONVECTION...WHILE THE BACK EDGE OF THE
HEAVIER RAINFALL GRADUALLY PUSHES EAST. AS NOTED EARLIER...MAXIMUM
OBSERVED RAINFALL REPORTS (2-4+ INCHES) REMAIN HIGHER THAN THE
RADAR ESTIMATES...INDICATIVE OF THE EFFICIENT WARM RAIN PROCESSES
WITH THE DEEP WARM CLOUD LAYER (WET BULB ZERO HEIGHTS ~14000 FT OR
HIGHER) AND HIGH PWS (AOA 2.25 INCHES PER THE 12Z KCHS RAOB AND
LATEST GPS DATA). CONTINUE TO EXPECT THE WIDESPREAD CLOUD
COVER/LACK OF DIFFERENTIAL HEATING AND WEAK/MOIST ADIABATIC LAPSE
RATES ALOFT TO LIMIT THE RAINFALL RATES IN AREAS FARTHER NORTH OF
THE WARM/STATIONARY FRONT...HOWEVER HIGHER MUCAPES (~1000 J/KG)
ALONG AND SOUTH OF THE SFC FRONTAL BNDRY CURRENTLY ACROSS NRN FL
(NEAR THE SE GA BORDER) WILL ENHANCE THE EXCESSIVE RAINFALL
POTENTIAL ACROSS SE GA/NRN FL...WHILE ALSO INTO EASTERN PORTIONS
OF THE FL PENINSULA GIVEN THE ENHANCED MOISTURE CONVERGENCE VIA
THE EAST COAST SEA BREEZE COMPONENT. WPC CONTINUED TO LEAN MORE
CLOSELY TO THE HIGHER RESOLUTION GUIDANCE IN TERMS OF TIMING AND
LOCATION OF HEAVIEST RAIN...AS ADDITIONAL AREAL-AVERAGE AMOUNTS
ARE EXPECTED TO RANGE BETWEEN 1-2+ INCHES FROM SE GA INTO MUCH OF
THE FL PENINSULA...THE BULK OF WHICH WILL OCCUR PRIOR TO 00Z. PER
THE HIGH RES GUIDANCE...ADDITIONAL LOCALIZED AMOUNTS OF 3-4+
INCHES ARE EXPECTED.

HURLEY
$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.