Quantitative Precipitation Forecast
Issued by NWS

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FOUS30 KWBC 300106
QPFERD

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

...VALID 03Z TUE SEP 30 2014 - 00Z WED OCT 01 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


PORTIONS OF THE CENTRAL AND NORTHERN HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
MESOSCALE PRECIPITATION DISCUSSION (MPD) #401 HAS BEEN ISSUED FOR
NORTHEAST CO, WESTERN NE, SOUTHEASTERN-MOST WY, AND
SOUTHWESTERN-MOST SD.  SEE THE MPD FOR MORE INFORMATION ON
EXCESSIVE RAINFALL CONCERNS IN THIS REGION PRIOR TO 03Z.

THE CLOSED MID/UPPER LEVEL LOW WILL LIFT NORTHEAST INTO THE
NORTHERN PLAINS AS A SHORTWAVE TROUGH AND ASSOCIATED UPPER JET
STREAK DROPS INTO THE PAC NW AND NORTHERN INTERMOUNTAIN WEST.  DUE
TO THE APPROACHING UPSTREAM TROUGH, THE LEADING SYSTEM TAKES ON A
NEGATIVE TILT UPON LIFTING OUT INTO THE CENTRAL/NORTHERN PLAINS ON
TUESDAY, LEADING TO STRONGER UPPER LEVEL DIFFLUENCE/DIVERGENCE AND
DEEP LAYER Q-VECTOR CONVERGENCE. THE MODELS SHOW THE UPPER
DIVERGENCE MAXIMIZING OVERNIGHT OVER THE WY/NORTHERN CO FOOTHILLS
AND INTO THE NORTHERN HIGH PLAINS.  AT LOW LEVELS...THE PRE-TROUGH
THERMODYNAMIC ENVIRONMENT BECOMES INCREASINGLY FAVORABLE GIVEN THE
INCREASING S-SE LOW-LEVEL AGEOSTROPHIC RESPONSE.  THE BEST
UVVS/UPPER DIVERGENCE IS EXPECTED 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 IN
THE HIGH PLAINS...THIS AREA SHOULD BE MORE OF A LONGER DURATION
FLOOD CONCERN RATHER THAN A FLASH FLOOD CONCERN.  THE 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 FAVOR MAXIMUM TERRAIN- ENHANCED RAINFALL
TOTALS (AREAL-AVERAGE AMOUNTS BETWEEN 1-3 INCHES).


NE/IA BORDER
~~~~~~~~~~~~
BROAD/STRONG 850 HPA INFLOW AHEAD OF THE HIGH PLAINS SYSTEM INTO A
FRONTAL BOUNDARY OF 25-40 KTS IS EXPECTED TO LEAD TO ORGANIZED
CONVECTION, WHICH SHOULD BE FORWARD PROPAGATING TOWARDS THE EAST
AT ~30 KTS.  EXPECTED INFLOW SHOULD BE ROUGHLY SIMILAR TO THE MEAN
850-400 HPA WIND, WHICH COULD LEAD TO PRECIPITATION EFFICIENCY
(HOURLY RATES UP TO 1.75" IN STRONGER STORMS).  A NARROW AXIS OF
1000-1500 J/KG CAPES ARE FORECAST NEAR THE NE/IA BORDER, WHICH
WOULD LIKELY BE THE INITIATION POINT FOR CONVECTION BEFORE IT
STREAKS EASTWARD.  THE BREADTH OF THE LOW-LEVEL INFLOW COULD LEAD
TO CELL TRAINING FROM EASTERNMOST NE INTO SOUTHWEST IA STARTING
15Z-18Z TUESDAY.  THE PRECIPITABLE WATER VALUES RISE CLOSE TO
1.50" -- THE GLOBAL GUIDANCE FALLS JUST SHY OF THIS MARK WHILE
RECENT RAP RUNS EXCEED THIS VALUE.  A SEE TEXT SHOULD TEMPORARILY
SATISFY THE EXPECTED CONCERN.  OUTFLOW BOUNDARIES FROM THE
CONVECTION SHOULD FORCE THE COMPOSITE BOUNDARY SOUTHWARD TOWARDS
KANSAS CITY BY EVENING, WHICH FITS IN NICELY WITH THE AREA
DEPICTED WITHIN THE ONGOING DAY 2 EXCESSIVE RAINFALL OUTLOOK.


EASTERN FL
~~~~~~~~~~
THERE REMAINS EXCESSIVE RAINFALL POTENTIAL ACROSS EASTERN PORTIONS
OF THE FL PENINSULA GIVEN THE ENHANCED MOISTURE CONVERGENCE
TOWARDS THE EAST COAST WHICH SHOULD BE FAVORED RAINFALL
MAGNITUDE-WISE DURING WEDNESDAY AFTERNOON/EVENING DUE TO THE
WEST-SOUTHWESTERLY LOW-LEVEL WIND FLOW.  RECENT RAP GUIDANCE
INDICATES 850 HPA INFLOW OF 20 KTS WITHIN A REGION OF >2" PWS,
WHICH COULD TRY TO ORGANIZE CONVECTION AS IT APPROACHES THE
REGION.  PER THE MOST RECENT NSSL QPE, THIS AREA RECEIVED 2-4" OF
RAINFALL DURING THE AFTERNOON AND EVENING MONDAY. PER THE HIGH RES
GUIDANCE...ADDITIONAL LOCALIZED AMOUNTS OF 3-4+ INCHES ARE
EXPECTED TUESDAY ACROSS THE PENINSULA.  CONSIDERING THE HIGH FLASH
FLOOD GUIDANCE IN THE REGION DUE TO SANDY SOILS AND SOME MARSHY
AREAS, DOWNGRADED THE AREA TO A "SEE TEXT" HIGHLIGHT.

ROTH
$$





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