683  
FOUS30 KWBC 220055  
QPFERD  
 
EXCESSIVE RAINFALL DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
855 PM EDT SAT JUN 21 2025  
 
DAY 1  
VALID 01Z SUN JUN 22 2025 - 12Z SUN JUN 22 2025  
 
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF  
THE NORTHERN GREAT LAKES AND THE INTERIOR NORTHEAST...  
 
01Z UPDATE...  
WITH SOME MINOR ADJUSTMENTS, MARGINAL RISK AREAS WERE MAINTAINED  
OVER PORTIONS OF NORTHERN MICHIGAN, AS WELL AS NORTHERN NEW YORK  
AND VERMONT.  
 
ACROSS NORTHERN MICHIGAN, THE LATEST HRRR HAS SHOWN AN UPTICK IN  
AMOUNTS CENTERED NEAR THE TIP OF THE MITT AND THE EASTERN U.P.,  
WHERE STORMS MAY DEVELOP AND LIFT NORTH FROM A SLOW-MOVING  
BOUNDARY. WHILE THE LATEST MESOANALYSIS SHOWS PLENTY OF MOISTURE  
(PWS 1.8+ INCHES) AND INSTABILITY (MUCAPE 3000+ J/KG), IT ALSO  
SHOWS A FAIR AMOUNT OF CIN, WHICH ALONG WITH A CAPPED ENVIRONMENT,  
IS LIKELY TO HINDER ANY WIDESPREAD DEVELOPMENT.  
 
FURTHER TO THE EAST, THE COMPLEX DEVELOPING OVER SOUTHWESTERN  
ONTARIO/SOUTHERN QUEBEC IS EXPECTED TO MOVE INTO NORTHERN NEW YORK  
AND NEW ENGLAND TONIGHT. THE LATEST GUIDANCE IS NOT INDICATING  
WIDESPREAD HEAVY AMOUNTS, HOWEVER A PERIOD OF TRAINING MAY  
CONTRIBUTE TO SOME LOCALIZED HEAVIER TOTALS (1-2 INCHES) AND AN  
ISOLATED FLASH FLOOD THREAT.  
 
PEREIRA  
 
PREVIOUS DISCUSSION...   
..NORTHERN GREAT LAKES  
 
CONVECTION WILL LIKELY BE ONGOING AT 12Z THIS MORNING ACROSS  
PORTIONS OF THE UP OF MI. IT STILL LOOKS LIKE THE STORM MODE SHOULD  
BE A PROGRESSIVE SQUALL LINE, WHICH WOULD LIMIT THE DURATION OF  
HEAVY RAINFALL AND FLASH FLOOD RISK. HOWEVER EVEN THE PROGRESSIVE  
CONVECTION WILL BE CAPABLE OF HEAVY RATES, WITH A HIGH LIKELIHOOD  
OF SOME 1"+ PER HOUR TOTALS, AND A LOW CHANCE OF 2" PER HOUR. ALSO  
CAN NOT RULE OUT SOME BRIEF BACKBUILDING/TRAINING ON THE SOUTHWEST  
FLANK OF CONVECTION AS IT MOVES EASTWARD. SO WHILE THE FLASH FLOOD  
RISK SHOULD BE RELATIVELY LOW, LOCALIZED HYDROLOGIC ISSUES CAN NOT  
BE RULED OUT THIS MORNING. CONVECTIVE AND MODEL TRENDS SUGGEST THE  
BETTER THREAT IS OVER THE UP OF MI, AND SO WE WERE ABLE TO CUT  
BACK ON THE SOUTHERN EXTENT OF THE INHERITED RISK AREA WITH THIS  
UPDATE.  
   
..NORTHEAST  
 
NOT EXPECTING MUCH CONVECTION DURING THE DAY ACROSS THE NORTHEAST,  
HOWEVER AN UPTICK IN ACTIVITY IS POSSIBLE OVERNIGHT INTO EARLY  
SUNDAY. BY TONIGHT STEEPER LAPSE RATES ADVECT INTO THE REGION,  
RESULTING IN WHAT SHOULD BE A PRETTY RAPID INCREASE IN MUCAPE OVER  
WESTERN NY INTO PORTIONS OF VT AND NH. THE ONGOING MCS OVER MN AND  
MI SHOULD WEAKEN AS IT APPROACHES THE NORTHEAST THIS EVENING AS  
INSTABILITY WILL NOT HAVE INCREASED YET. HOWEVER THE PARENT MID  
LEVEL SHORTWAVE WILL REMAIN UPSTREAM AND EXPECT AN ADDITIONAL AREA  
OF ORGANIZED CONVECTION TO DEVELOP WITH THIS OVER SOUTHERN CANADA.  
IT IS THIS NEXT ROUND THAT HAS A BETTER CHANCE OF SURVIVING INTO  
PORTIONS OF NY/VT/NH BY LATER TONIGHT.  
 
THE DETAILS OF THIS REMAIN UNCLEAR, BUT THERE SHOULD BE ENOUGH  
INSTABILITY AND LOW LEVEL MOISTURE TRANSPORT/CONVERGENCE TO  
SUSTAIN SOME LEVEL OF ACTIVITY INTO THE NORTHEAST. MOST INDICATIONS  
FROM THE 00Z HIGH RES GUIDANCE IS FOR A QUICK MOVING AREA OF  
CONVECTION, AND THUS RAINFALL TOTALS ARE NOT OVERLY IMPRESSIVE.  
HOWEVER GIVEN THE INGREDIENTS IN PLACE THERE DOES SEEM TO BE SOME  
POTENTIAL FOR AN OVER PERFORMING AREA OF CONVECTION WITH SOME BRIEF  
BACKBUILDING CHARACTERISTICS. THE BETTER CHANCE OF THIS WOULD BE  
ALONG THE INSTABILITY GRADIENT AND SOUTHWEST FLANK OF  
ACTIVITY...PROBABLY CENTRAL/UPSTATE NY AND/OR PORTIONS OF VT/NH. A  
MARGINAL RISK CONTINUES TO SUFFICE GIVEN THE 00Z SUITE OF  
MODELS...HOWEVER WILL NEED TO CLOSELY MONITOR OBSERVATIONAL AND  
MODEL TRENDS THROUGH THE DAY. DEPENDING ON HOW THINGS EVOLVE LATER  
TONIGHT INTO EARLY SUNDAY THERE IS SOME CHANCE FOR AN EMBEDDED  
MORE FOCUSED FLASH FLOOD RISK WITHIN THE BROADER MARGINAL, AND CAN  
NOT RULE OUT THE EVENTUAL NEED FOR A SLIGHT RISK.  
 
CHENARD  
 
DAY 2  
VALID 12Z SUN JUN 22 2025 - 12Z MON JUN 23 2025  
 
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF  
SOUTHEAST NEW MEXICO AND SOUTHWEST TEXAS...  
 
2030Z EXCESSIVE RAINFALL DISCUSSION UPDATE...  
LATEST NUMERICAL GUIDANCE REMAINED IN GOOD AGREEMENT WITH PREVIOUS  
RUNS ABOUT THE LARGE-SCALE FEATURES AND THE ASSOCIATED INCREASE IN  
THE RISK OF EXCESSIVE RAINFALL BEGINNING AS EARLY AS SUNDAY. AS A  
RESULT...LITTLE CHANGE WAS NEEDED TO THE EXCESSIVE RAINFALL  
OUTLOOK FOR SUNDAY.  
 
BANN  
 
PREVIOUS EXCESSIVE RAINFALL DISCUSSION...  
   
..NEW MEXICO AND TEXAS  
 
SUNDAY IS LIKELY THE BEGINNING OF WHAT WILL BE A MULTI-DAY PERIOD  
OF EXCESSIVE RAINFALL POTENTIAL OVER PORTIONS OF WEST TX INTO NM.  
THE MID/UPPER LEVEL PATTERN FEATURES A NEAR RECORD TO RECORD RIDGE  
OVER THE EASTERN U.S. AND A WELL-DEFINED LONGWAVE TROUGH OVER THE  
WEST. SOUTHERLY FLOW IN BETWEEN THESE FEATURES WILL SUPPLY AMPLE  
MOISTURE TO NM, WITH A CONNECTION ALL THE WAY TO THE CARIBBEAN SEA.  
THE BETTER FORCING FROM THE WESTERN TROUGH WILL GENERALLY HOLD OF  
UNTIL MONDAY AND TUESDAY (SEE THE DAY 3 AND 4 EROS), BUT BY SUNDAY  
WE SHOULD AT LEAST HAVE ENOUGH MOISTURE AND INSTABILITY AROUND FOR  
SCATTERED CONVECTIVE DEVELOPMENT. IN FACT PWS BY SUNDAY SHOULD  
ALREADY BE GETTING TOWARDS CLIMATOLOGICAL MAX VALUES FOR LATE JUNE  
OVER PORTIONS OF SOUTHWEST TX AND IMMEDIATE ADJACENT AREAS OF NM.  
AND WHILE THE BETTER FORCING ARRIVES MONDAY, DO NOTE BROADLY  
DIVERGENT FLOW AT 250MB SUNDAY WHICH COULD HELP SUSTAIN CONVECTION.  
 
GIVEN THESE INGREDIENTS WE WENT AHEAD AND UPGRADED TO A SLIGHT RISK  
FOR PORTIONS OF SOUTHWEST TX INTO OTERO AND EDDY COUNTIES IN NM.  
EXPECTING ENOUGH CONVECTIVE DEVELOPMENT SUNDAY AFTERNOON/EVENING,  
THAT COMBINED WITH THE NEAR RECORD PWS, SUGGESTS AN ISOLATED TO  
SCATTERED FLASH FLOOD RISK SHOULD EVOLVE OVER THESE AREAS. A BIT  
OF UNCERTAINTY WITH HOW FAR NORTH THE SLIGHT SHOULD EXTEND INTO NM  
WITH SOME MODELS SUPPORTING A FARTHER NORTH EXPANSION. HOWEVER THE  
AREA CURRENTLY HIGHLIGHTED SHOWS THE BEST OVERLAP OF THE  
NAM/RRFS/ECMWF AND LIKELY HAS THE HIGHER PROBABILITY OF SEEING  
FLASH FLOODING AT THE MOMENT. THE BROAD MARGINAL RISK DOES STILL  
EXTEND INTO MUCH OF THE REST OF EASTERN NM AND COVERS THE  
LOCALIZED RISK OVER THOSE AREAS.  
   
..NORTHERN MINNESOTA  
 
WENT AHEAD AND ADDED A SMALL MARGINAL RISK OVER PORTIONS OF  
NORTHERN MN WITH THIS UPDATE. THE SETUP LOOKS FAVORABLE FOR ANOTHER  
ROUND OF ORGANIZED CONVECTION SUNDAY AFTERNOON AND EVENING ACROSS  
THIS REGION. STRONG SHORTWAVE ENERGY EJECTING INTO THE NORTHERN  
PLAINS, A STRENGTHENING AXIS OF LOW LEVEL MOISTURE TRANSPORT, AND  
UPWARDS OF 4000 J/KG OF MUCAPE WILL DRIVE THE CONVECTIVE THREAT.  
THE COMBINATION OF EXTREME INSTABILITY, PWS WELL OVER THE 90TH  
PERCENTILE FOR LATE JUNE, AND A WARM FRONT FOCUSING CONVECTION, ALL  
POINT TO A HEAVY RAINFALL THREAT. SOME UNCERTAINTY WITH THE EXACT  
AXIS OF CONVECTION, WITH SOME GUIDANCE FOCUSING THE BULK OF  
CONVECTION FARTHER NORTH INTO CANADA. HOWEVER BOTH GEFS AND ECENS  
PROBS SUGGEST SOME RISK INTO NORTHERN MN, AND THE AIFS (WHICH HAS A  
HISTORY OF GOOD CONVECTIVE QPF PLACEMENT) ALSO FAVORS NORTHERN MN.  
QUITE POSSIBLE CONVECTION ENDS UP BLOWING THROUGH QUICKLY, SO NO  
NEED FOR ANYTHING MORE THAN A MARGINAL RISK AT THIS TIME. BUT WILL  
NEED TO CONTINUE TO MONITOR TRENDS OVER THE COMING DAYS.  
 
CHENARD  
 
DAY 3  
VALID 12Z MON JUN 23 2025 - 12Z TUE JUN 24 2025  
 
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF  
NEW MEXICO AND WEST TEXAS, AND FROM KANSAS INTO IOWA...  
 
2030Z EXCESSIVE RAINFALL DISCUSSION UPDATE...  
LATEST NUMERICAL GUIDANCE REMAINED IN GOOD AGREEMENT WITH PREVIOUS  
RUNS ABOUT THE LARGE-SCALE FEATURES AND THE ASSOCIATED  
INCREASING AREAL COVERAGE OF MODERATE TO HEAVY  
RAINFALL...ESPECIALLY IN NEW MEXICO AND WEST TEXAS AS WELL AS  
ACROSS PARTS OF THE MISSOURI VALLEY ON MONDAY/MONDAY NIGHT. AS A  
RESULT...LITTLE CHANGE WAS NEEDED TO THE PREVIOUSLY ISSUED EXCESSIVE  
RAINFALL OUTLOOK FOR DAY 3.  
 
BANN  
   
..SOUTHWEST  
 
THE OVERALL PATTERN OVER THE SOUTHWEST DESCRIBED IN THE DAY 2  
DISCUSSION WILL PERSIST INTO THE DAY 3 PERIOD. BY DAY 3 FORCING,  
MOISTURE AND INSTABILITY SHOULD ALL BE ON THE INCREASE, AND THUS  
EXPECT CONVECTIVE COVERAGE AND FLASH FLOOD RISK TO BE ON THE  
RISE AS WELL. THE GRADUAL APPROACH OF THE WEST COAST TROUGH WILL  
BRING THE RIGHT ENTRANCE REGION OF THE UPPER JET CLOSER, AND  
CONTINUED MOISTURE ADVECTION IN BETWEEN THE TROUGH AND THE EAST  
COAST RIDGE WILL PUSH PWS WELL ABOVE THE CLIMATOLOGICAL 90TH  
PERCENTILE AND TOWARDS LATE JUNE MAX LEVELS. INSTABILITY IS A BIT  
OF A QUESTION AS CLOUD COVER DEBRIS FROM SUNDAYS ACTIVITY COULD  
PLAY A ROLE...HOWEVER THE MODEL CONSENSUS IS FOR INCREASED  
INSTABILITY COMPARED TO SUNDAY, WITH VALUES AVERAGING 1000-2000  
J/KG OVER MUCH OF EASTERN NM INTO FAR WEST TX. NOT A TON OF DEEP  
LAYER FLOW, SO CONVECTION FORMING ON/NEAR TERRAIN SHOULD SLOWLY  
MOVE OFF THE TERRAIN AND ALLOW FOR SOME CELL MERGER ACTIVITY. THE  
EXPECTED CONVECTIVE COVERAGE SHOULD EVENTUALLY ERODE INSTABILITY  
ENOUGH THAT ACTIVITY TRENDS DOWN BY OVERNIGHT...BUT NOT BEFORE WHAT  
SHOULD BE A MORE WIDESPREAD ISOLATED/SCATTERED FLASH FLOOD RISK  
OVER EASTERN NM AND WEST TX WHERE A SLIGHT RISK REMAINS. THE  
WESTERN EDGE OF THIS RISK AREA WAS ADJUSTED EASTWARD A TAD, AS  
MODEL TRENDS NOW SUPPORT A SLIGHTLY FARTHER EAST AXIS.  
 
SOME UNCERTAINTY ON WHERE ANY MORE FOCUSED RISK COULD EVOLVE, BUT  
THE BETTER MODEL CLUSTERING IS OVER SOUTHWEST TX INTO SOUTHEAST NM  
AND CONSIDER THE THREAT OVER THIS CORRIDOR A HIGHER END SLIGHT  
RISK. THIS INCLUDES THE SENSITIVE SACRAMENTO MOUNTAIN BURN SCAR  
AREAS, WHERE LOCALIZED SIGNIFICANT FLASH FLOOD IMPACTS ARE A  
POSSIBILITY.  
   
..CENTRAL PLAINS TO MS VALLEY  
 
A SLIGHT RISK REMAINS FROM PORTIONS OF CENTRAL KS INTO SOUTHEAST  
NE AND MUCH OF CENTRAL AND NORTHERN IA WHERE CONVECTION ALONG A  
STATIONARY FRONT POSES AN ISOLATED TO SCATTERED FLASH FLOOD RISK.  
MODEL GUIDANCE INDICATES CONVECTIVE DEVELOPMENT ALONG/NEAR THIS  
FRONT MONDAY AFTERNOON, WITH SOME PERSISTENCE AND/OR UPSCALE  
DEVELOPMENT POSSIBLE MONDAY EVENING AS LOW LEVEL MOISTURE  
TRANSPORT INCREASES. CORFIDI VECTORS OVER THIS AREA ARE DIVERGENT,  
INDICATING A FAVORABLE ENVIRONMENT FOR SLOW MOVING/BACKBUILDING  
CONVECTION NEAR THIS FRONT. PWS SHOULD BE WELL OVER THE 90TH  
PERCENTILE FOR LATE JUNE ALONG THIS FRONT, AS THE SAME PLUME OF  
MOISTURE OVER THE SOUTHWEST WILL BE IN PLACE HERE AS WELL. THUS  
ANY TRAINING OF CONVECTION WILL POSE A FLASH FLOOD RISK.  
MAINTENANCE OF INSTABILITY IS PROBABLY THE MAIN QUESTION MARK, AS  
THE POOL OF FORECAST INSTABILITY IS NOT OVERLY IMPRESSIVE AND  
NEITHER IS THE MAGNITUDE OF THE LOW LEVEL JET...SO THE EXTENT OF  
CONVECTIVE PERSISTENCE INTO THE OVERNIGHT IS A BIT UNCLEAR.  
NONETHELESS, THE UNANIMOUS MODEL SIGNAL FOR ORGANIZED CONVECTIVE  
DEVELOPMENT, COMBINED WITH THE STATIONARY FRONT/CONVERGENCE AND  
HIGH PWS SUPPORTS AT LEAST AN ISOLATED TO SCATTERED FLASH FLOOD  
POTENTIAL. THUS THE SLIGHT RISK WAS MAINTAINED. OVERALL MODELS ARE  
IN FAIRLY GOOD AGREEMENT WITH THE FAVORED CONVECTIVE AXIS, AND THUS  
NOT MUCH CHANGE WAS NEEDED TO THE INHERITED RISK AREA.  
 
CHENARD  
 
DAY 1 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT  
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT  
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT  
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