Quantitative Precipitation Forecast
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000 FOUS30 KWBC 291404 QPFERD EXCESSIVE RAINFALL DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1003 AM EDT WED JUN 29 2016 ...VALID 15Z WED JUN 29 2016 - 12Z THU JUN 30 2016... ...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL... SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 25 SW MLT IZG HIE 30 NNE CWHV 25 NW CERM 10 E CYSL 25 SW MLT. SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 W GAG 35 SSE GCK 35 WNW GCK 50 NNW GCK 25 SSW HYS 20 E P28 20 NNE CSM 35 WNW LTS 40 N CDS 20 W GAG. ...NEW ENGLAND... AS AN UPPER TROUGH SWINGS AROUND TOWARD NEUTRAL OR NEGATIVE TILT...WIDESPREAD ASCENT WILL CONTINUE TO CRATE A FAVORABLE ENVIRONMENT FOR WIDESPREAD PRECIPITATION AND EMBEDDED CONVECTIVE PRECIPITATION. SOME FLASH FLOODING COULD OCCUR WHERE GUIDANCE VALUES HAVE BEEN LOWERED. GEFS V-COMPONENT 700 MB WIND ANOMALIES LIGHT UP AT 2 OR MORE STANDARD DEVIATIONS FROM CLIMATOLOGY...SUGGESTING SOME TERRAIN ENHANCEMENT...ESPECIALLY EARLY IN THE DAY. SOME DIURNAL TRENDS IS ALSO LIKELY TO BE NOTED...WITH A FLARE-UP OF HEAVIER RAIN RATES IN THE LATE MORNING TO EARLY AFTERNOON HOURS...ESPECIALLY OVER CENTRAL MAINE. MOST MODEL GUIDANCE PRODUCES A GRADUAL ACCUMULATION OF 1.0 TO 1.25 INCHES...AREAL AVERAGE...OVER THE SLIGHT RISK AREA...THOUGH HOURLY RATES WILL AT TIMES APPROACH 1.0 INCH PER HOUR...WHICH MAY EXCEED FLASH FLOOD GUIDANCE...PARTICULARLY IN AREAS THAT RECEIVED LOCALLY HEAVY RAIN ON TUESDAY. ...SOUTHERN ARIZONA... COMPACT...CONVECTIVELY-AIDED VORT LOBE NEAR THE AZ/MEXICAN BORDER ALONG WITH THE STEADILY IMPROVING DEEP-LAYER MOISTURE PROFILE WILL ONCE AGAIN ALLOW FOR THE DEVELOPMENT OF SCATTERED-NUMEROUS SHOWERS AND TSTMS DURING THE PEAK HEATING HOURS OF THE AFTERNOON AND EVENING. AS WITH YESTERDAY...EXPECT THE BULK OF THE ACTIVITY TO BEGIN ACROSS THE HIGHER TERRAIN IN SOUTHEAST AZ (FUELED BY E-SE LOW LEVEL INFLOW AROUND 15-20 KTS)...THEN PUSH W TO WSW INTO THE THE LOWER ELEVATIONS ACROSS SOUTH-CENTRAL AZ PER THE CORFIDI VECTORS IN THE OVERALL WEAK FLOW ENVIRONMENT. BOTH THE PRECIPITABLE WATER AND 850-700 MB MOISTURE FLUX ANOMALIES ARE QUITE HIGH FOR LATE JUNE -- AROUND 3 STANDARD DEVIATIONS ABOVE NORMAL PER BOTH THE SREF AND GEFS -- WHICH COMBINED WITH THE MODEST DIURNAL INSTABILITY (MUCAPES GENERALLY 1000-1500 J/KG)... ENHANCED LIFT SUPPORT AND FOCUSED LOW-LEVEL INFLOW VIA THE SHORTWAVE...WILL MAKE FOR LOCALIZED SHORT-TERM RUNOFF ISSUES AS WAS OBSERVED YESTERDAY. ...CENTRAL PLAINS... EARLY THIS MORNING A RELATIVELY EXTENSIVE LINE OF ORGANIZED CONVECTION WAS ROLLING OUT OF THE HIGH PLAINS. IN TERMS OF LONGEVITY GOING FORWARD...THERE ARE TWO CORRIDORS WHERE ADDITIONAL SIGNIFICANT PRECIPITATION IS FAVORED...ONE BEING THE MID MISSOURI VALLEY WHERE UPGLIDE AND THE ARRIVAL OF A SOMEWHAT ENERGETIC SHORTWAVE WILL PRODUCE FAVORABLE SYNOPTIC LIFT. THE HRRR...NSSL WRF...AND WRF-ARW HIT THIS AREA PRETTY WELL...WITH MODERATELY HEAVY RAINFALL FROM EASTERN NE / WESTERN IA WHICH WE THEN PROGRESS DOWN THROUGH EASTERN KS / WESTERN MO DESPITE RELATIVELY WEAKER MODEL SIGNAL DOWN THERE. THE ONE THAT SEEMS TO HOLD ONTO THAT SIGNAL THE BEST IS THE NSSL WRF...WHICH HAS PERFORMED WELL IN RECENT WEEKS. THE OTHER FAVORABLE CORRIDOR IS DOWN THROUGH WESTERN KS INTO ADJACENT PARTS OF OK/TX. THERE MAY BE A LIMIT TO HOW EFFECTIVE CONVECTION CAN BE THIS MORNING...SINCE MUCH OF THE AREA WAS OVERTURNED...ESPECIALLY IN WESTERN OK...LATE TUESDAY. GENERALLY SPEAKING...HOWEVER...THE CORRIDOR FROM EASTERN CO INTO SW KS AND ADJACENT OK/TX LOOKS TO HAVE THE GREATEST OVERLAP OF INSTABILITY AND LOW LEVEL INFLOW / LOW LEVEL JET THROUGHOUT THE DAY 1 PERIOD...AND A SLIGHT RISK OF EXCESSIVE RAINFALL WAS INCLUDED IN PARTS OF THIS REGION BASED ON THE COMBINATION OF MANUAL QPF AND RECENT RAIN SWATHS / LOWERED FFG. ...GEORGIA AND SOUTH CAROLINA... HIGH PRECIPITABLE WATER VALUES REMAIN SWEPT UP ON THE SOUTH SIDE OF A BAROCLINIC ZONE WITH PRE-FRONTAL TROUGH / EFFECTIVE FRONT IN PLACE NEAR COASTAL SOUTH CAROLINA AND SOUTHERN GEORGIA. THIS SETUP...WITH PW VALUES OVER 1.75 INCHES...STRONG JUNE SUN ANGLE...AND AMPLE LIFTING FROM SEA BREEZES AND WEAKLY FAVORABLE SYNOPTIC BACKGROUND TROUGHING...SHOULD AGAIN LEAD TO SCATTERED AND SLOWLY PROPAGATING THUNDERSTORMS CAPABLE OF PRODUCING INTENSE DOWNPOURS. MESONET STATIONS AROUND SAVANNAH GEORGIA MEASURED MORE THAN 3 INCHES OF RAIN ON TUESDAY. LOWER TO MIDDLE LEVEL WINDS WILL NOT BE QUITE SO FOCUSED FOR PRODUCING LIFT ON WEDNESDAY...BUT ISOLATED INTENSE DOWNPOURS ARE STILL LIKELY AS SEEN IN MOST OF THE HI-RES MODEL OUTPUT. SOME FLASH FLOODING COULD OCCUR...ESPECIALLY WHERE GUIDANCE VALUES HAVE BEEN LOWERED BY THE RECENT RAINFALL. ...SOUTHERN LOUISIANA AND SOUTHERN MISSISSIPPI... FLASH FLOOD GUIDANCE VALUES HAD FALLEN...OWING TO SATURATION ASSOCIATED WITH HEAVY RAIN THAT OCCURRED TUESDAY OVER PARTS OF SOUTHERN LOUISIANA. ADDITIONAL SCATTERED HEAVY RAIN IS EXPECTED TODAY...ALTHOUGH THE SYNOPTIC FORCING WILL CONTINUE TO SLIDE SOUTHWARD...PUSHING GREATER COVERAGE OF HEAVY RAIN TOWARD THE COAST...AND AWAY FROM THE AREAS AFFECTED YESTERDAY. SOME FLASH FLOODING COULD OCCUR...ESPECIALLY WHERE GUIDANCE VALUES HAVE BEEN LOWERED BY THE RECENT RAINFALL. BURKE/HURLEY $$

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