769
FOUS30 KWBC 271600
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT SAT JUN 27 2026
DAY 1
VALID 16Z SAT JUN 27 2026 - 12Z SUN JUN 28 2026
...THERE IS A MODERATE OF EXCESSIVE RAINFALL OVER PORTIONS OF THE
OHIO VALLEY...
1600Z UPDATE...
BASED ON A CONSENSUS OF THE 12Z HREF/REFS GUIDANCE ALONG WITH
RECENT HRRR/RRFS SOLUTIONS, AND THE CURRENT RADAR/SATELLITE TRENDS,
IT HAS BEEN DECIDED TO UPGRADE PORTIONS OF THE OH VALLEY TO A
MODERATE RISK OF EXCESSIVE RAINFALL. MULTIPLE ROUNDS OF VERY HEAVY
RAINFALL WITH LOCALLY EXTREME RAINFALL RATES OF 2 TO 3 INCHES/HOUR
HAVE BEEN OCCURRING ALREADY THIS MORNING LOCALLY ACROSS AREAS OF
FAR SOUTHERN IN DOWN THROUGH CENTRAL KY WITH RATHER WIDESPREAD
FLASH FLOODING ONGOING. THE LATEST SATELLITE IMAGERY SHOWS A PARADE
OF MCVS TRANSITING THE MID MS AND OH VALLEY REGION WITH THE DEEPER
LAYER, BUT VERY MOIST WEST-SOUTHWEST FLOW ACROSS THE REGION. VERY
HIGH PWS RUNNING 2 TO 2.5+ STANDARD DEVIATIONS ABOVE NORMAL AND
TALL, SKINNY CAPE PROFILES SUPPORT HIGH-END RAINFALL POTENTIAL AND
ESPECIALLY WITH WEAK AND LOCALLY OPPOSING CORFIDI VECTORS ACROSS
SIZABLE AREAS OF THE OH VALLEY. THERE IS SOME VARIANCE WITH RESPECT
TO THE DETAILS OF THE CONVECTIVE BAND EVOLUTIONS GOING THROUGH THIS
AFTERNOON AND EVENING AS BASICALLY EACH VORT CENTER WILL BE
POTENTIALLY ABLE TO FOCUS ITS OWN AXIS OF VERY HEAVY RAINFALL.
THERE IS EVIDENCE TO SUPPORT A NOCTURNAL LOW-LEVEL JET ENHANCEMENT
TONIGHT WITH RESPECT TO THE CURRENT MCV OVER SOUTHERN MO AS THIS
FEATURE ADVANCES DOWNSTREAM INTO WESTERN AND CENTRAL KY. SEVERAL
HIRES CAM MEMBERS SUPPORT A THREAT FOR A HIGH-END TRAINING BAND OF
CONVECTION OVER PARTS OF CENTRAL/SOUTHERN KY AND POSSIBLY NORTHERN
TN. ADDITIONAL RAINFALL AMOUNTS NEAR AND ADJACENT TO THE MODERATE
RISK AREA COULD LOCALLY APPROACH 3 TO 6+ INCHES.
ELSEWHERE, AN EXPANSION OF THE MARGINAL RISK AREA WAS ACCOMMODATED
ACROSS THE NORTHERN PLAINS IN CONNECTION TO THE DEEPER LAYER TROUGH
OVER THE INTERMOUNTAIN WEST THAT WILL BE EJECTING GRADUALLY OFF TO
THE EAST. EXPECTING A RATHER WELL-ORGANIZED OUTBREAK OF
THUNDERSTORMS ACROSS ARES OF THE NORTHERN HIGH PLAINS WITH
DOWNSTREAM ADVANCE OF ACTIVITY ACROSS THE DAKOTAS. SOME LOCALIZED
FLASH FLOODING CONCERNS WILL BE POSSIBLE.
FINALLY, A MARGINAL RISK HAS BEEN INTRODUCED ACROSS AREAS OF THE
SOUTHERN HIGH PLAINS AND MAINLY FOR WESTERN AND SOUTHWEST TX AS A
CHANNEL OF DEEPER LAYER MOISTURE COUPLED WITH THE EJECTION OF A
WEAK MCV/SHORTWAVE OUT OF SOUTHEAST NM HELPS TO INITIATE AND FOCUS
CONVECTION WITH THE DIURNAL HEATING CYCLE. GIVEN LOCAL TERRAIN-
FOCUSED SENSITIVITIES, A LOCALIZED THREAT OF FLASH FLOODING WILL BE
POSSIBLE HERE LATER TODAY AND THIS EVENING.
ORRISON
PREVIOUS DISCUSSION...
..MID-MISSISSIPPI VALLEY THROUGH SOUTHERN APPALACHIANS
ANOTHER EXPANSION OF A HIGH-END SLIGHT RISK AREA WAS MADE ALONG A
WEST TO EAST AXIS BASED ON CONVECTION OCCURRING PRIOR TO THE START
OF THE OUTLOOK PERIOD AT 27/12Z...WITH THE EXPECTATION THAT THE
RISK PERSISTS THROUGH MUCH OF THE DAY 1 PERIOD IN PROXIMITY TO AN
EAST-WEST ORIENTED STATIONARY FRONT. LOW LEVEL WESTERLY FLOW
REMAINS PARALLEL TO THIS BOUNDARY, RAISING CONCERNS FOR
REPEATING/TRAINING ACTIVITY. THE 27/00Z HRRR AND THE 27/00 RRFS QPF
PLACEMENT WAS SIMILAR TO EACH OTHER...BUT THE RRFS APPEARED TO BE
SHOWINGS ITS BIAS WITH HIGHER QPF AND HIGHER NEIGHBORHOOD
PROBABILITIES OF EXCEEDANCE. THE CONCERN IS GREATEST UPON OVERLAP
OF ANY ADDITIONAL RAINFALL WITH THE FOOTPRINT OF RECENT HEAVY
RAINFALL EVENTS.
..MID-ATLANTIC
00Z GUIDANCE OFFERED A SPLIT DECISION OF WHETHER OR NOT A FRONTAL
ZONE LINGERS OVER THE CENTRAL MID- ATLANTIC THROUGH TONIGHT RATHER
THAN SHIFTING SHIFTING SOUTH TO THE VIRGINIA/NORTH CAROLINA BORDER.
ASSUMING IT STAYS OVER THE MID-ATLANTIC...ENHANCED MOISTURE AND
INSTABILITY WILL REMAIN OVER THE DC AREA METROS AND THE DELMARVA
WITH A RISK OF ISOLATED HEAVY TO EXCESSIVE RAINFALL OTHERWISE THE
FOCUS SHIFTS SOUTH WITH TIME. DESPITE THAT UNCERTAINTY...ANY
STORMS THAT FORM IN SUCH AN AIRMASS CAN EASILY PRODUCE LOCALIZED
DOWNPOURS AND EXCESSIVE RAINFALL. THIS STILL LOOKS TO BE A
LOCALIZED FLASH FLOOD THREAT, BUT A FOCUSED SLIGHT RISK MAY BE
NEEDED EVENTUALLY.
..NORTHERN PLAINS
THE UPPER LOW TRACKS OVER THE INTERIOR NORTHWEST ON TODAY WITH A
SHORTWAVE TROUGHING EJECTING ACROSS NORTHERN WYOMING AND EASTERN
MONTANA BY THIS EVENING. LOW LEVEL FORCING EAST OF THE APPROACHING
WAVE TRIGGERS REPEATING THUNDERSTORMS OVER EASTERN MONTANA THROUGH
NORTH DAKOTA FROM THIS AFTERNOON INTO THE EVENING. INCREASING LOW
LEVEL JET SHOULD ENHANCE RAINFALL WITHIN THE SLIGHT RISK
MAINTAINED/EXPANDED EASTWARD IN NORTH DAKOTA. ACTIVITY SHOULD BE
FAIRLY PROGRESSIVE, BUT THE ROUTE OF THE UPPER TROUGH MAY
PIVOT/ALLOW REPEATING ACTIVITY.
BANN/JACKSON
DAY 2
VALID 12Z SUN JUN 28 2026 - 12Z MON JUN 29 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN NORTHWEST
MONTANA AND PORTIONS OF THE UPPER MIDWEST...
..MONTANA
UPPER LOW CENTER PIVOTS OVER MONTANA SUNDAY WITH THE SURFACE LOW
STALLING ALONG THE INTERNATIONAL BORDER . THIS MAINTAINS COMMA
HEAD/DEFORMATION ZONE RAIN SHIFTING INTO NORTHWEST MT WHERE TERRAIN
ENHANCES RATES AT LOWER ELEVATIONS AND SNOW GENERALLY AT OR ABOVE
6500 FEET. THIS IS MORE OF AN AREAL FLOOD CONCERN GIVEN A LACK OF
INSTABILITY, BUT LOCALIZED RATES MAY WARRANT SOME RAPID FLOODING
CONCERNS WHERE PRECIP BANDS ARE MOST STAGNANT. 00Z CONSENSUS
RAINFALL REMAINED IN THE 1 TO 3 INCH RANGE AROUND GLACIER NATIONAL
PARK ONTO THE ADJACENT HIGH PLAINS IN NORTHWEST MT. A MARGINAL
RISK WAS MAINTAINED FOR THIS AREA.
..UPPER MIDWEST
THE WARM SECTOR OF THIS ANOMALOUS LOW OVER MT WILL SHIFT EASTWARD
ALLOWING AN AIRMASS WITH ROBUST GULF MOISTURE ADVECTION UP THE
LENGTH OF THE GREAT PLAINS THROUGH THE UPPER MIDWEST. THE
DEVELOPMENT OF SURFACE LOW PRESSURE OVER SOUTH DAKOTA WILL AID THE
MOISTURE TRANSPORT AT THE LOW LEVELS AND PROVIDE A LIFTING
MECHANISM. FOCUSING ON THIS...THERE WAS AN EASTWARD EXPANSION AND A
BIT OF A SOUTHWARD EXPANSION OF THE PREVIOUSLY ISSUED MARGINAL
RISK AREA.
..COASTAL CAROLINAS/MID-ATLANTIC
ADDED A SMALL, TARGETED MARGINAL ALONG THE EASTERN SEABOARD WHERE
PRECIPITATION LINGERS FROM THE DAY 1 PERIOD. BLENDING DISPARATE QPF
IN SUCH CASES TENDS TO YIELD LOW AMOUNTS...BUT THE AREA HAD THE
BEST OVERLAP WITH HIGHEST PRECIPITABLE WATER VALUES AND AN AREA
WHERE ENSEMBLE MEMBERS WITH DIFFERING CORES TENDED TO CLUSTER. WITH
SUCH HIGH MOISTURE...LOCALIZED DOWNPOURS AND HEAVY TO EXCESSIVE
RAINFALL IS A CONCERN FROM ANY STORM THAT CAN DEVELOP REGARDLESS OF
THE MEAGER FOCUSING MECHANISM.
BANN/JACKSON
DAY 3
VALID 12Z MON JUN 29 2026 - 12Z TUE JUN 30 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GREAT LAKES REGION AND SOUTHWEST TEXAS...
GREAT LAKES...
SHIFTED THE MARGINAL RISK AREA FROM DAY 2 EASTWARD INTO THE WESTERN
PORTION OF THE GREAT LAKES REGION AS THE FEED OF LOW LEVEL
MOISTURE FROM THE PLAINS SHIFTS IN ASSOCIATION WITH THE PARENT
SYSTEM. GIVEN RECENT CONDITIONS...ONLY PROBLEMS ARE EXPECTED IN
REGIONS OF POOR DRAINAGE OR SMALL STREAMS.
SOUTHWEST TEXAS...
INCREASING INSTABILITY SHOULD LEAD TO LATE DAY CONVECTIVE
DEVELOPMENT ALONG AND NEAR THE DRY LINE IN SOUTHWEST TEXAS.
ISOLATED HEAVY RAINFALL MAY RESULT AS MOISTURE FROM THE GULF GETS
DRAWN NORTHWESTWARD IN TIME...WITH A LOW END POTENTIAL FOR
EXCESSIVE RAINFALL ASSOCIATED WITH THE MOST ACTIVE CONVECTION.
BANN
DAY 4 AND DAY 5
VALID 12Z TUE JUN 30 2026 - 12Z THU JUL 02 2026
DAY 4
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN HIGH PLAINS, UPPER MISSISSIPPI VALLEY/UPPER LAKES REGION
AND ACROSS NORTHERN NY STATE INTO NORTHERN NEW ENGLAND...
..NORTHERN NEW YORK STATE INTO NORTHERN NEW ENGLAND
SHORTWAVE ENERGY RIDING UP OVER THE TOP OF THE OHIO VALLEY UPPER
HIGH ACROSS SOUTHEAST CANADA INTO NORTHERN NEW ENGLAND WILL HELP
STRENGTHEN THE LOW LEVEL WESTERLY FLOW INTO THE FRONTAL BOUNDARY
FORECAST TO STRETCH NORTHWEST TO SOUTHEAST FROM EASTERN ONTARIO
INTO NORTHERN NY STATE AND NORTHERN NEW ENGLAND LATE TUE AFTERNOON
INTO TUESDAY NIGHT. THERE IS POTENTIAL FOR ORGANIZED CONVECTION IN
THE 0000 TO 1200 UTC JULY 1 PERIOD ALONG AND NORTH OF THIS
BOUNDARY. THE GFS AND EC CONTINUE TO BOTH SHOW PW VALUES BECOMING
VERY ANOMALOUS ALONG AND JUST NORTH OF THIS FRONT, WITH VALUES
2.5-3+ STANDARD DEVIATION ABOVE THE MEAN. WHILE THERE IS STILL A
LOT OF SPREAD WITH QPF DETAILS AT THIS TIME RANGE, THERE IS A MODEL
SIGNAL FOR ORGANIZED CONVECTION MOVING NORTHWEST TO SOUTHEAST
RESULTING IN HEAVY RAINS AND ISOLATED RUNOFF ISSUES.
..SOUTHERN HIGH PLAINS
PW VALUES EXPECTED TO RISE TO 1 TO 1.5+ STANDARD DEVIATIONS ABOVE
THE MEAN IN THE BROAD SOUTHWEST MID TO UPPER LEVEL FLOW ACROSS THE
SOUTHERN HIGH PLAINS ON THE WEST SIDE OF THE LOWER MS CLOSED UPPER
HIGH. EMBEDDED SHORTWAVES IN THIS SOUTHWEST MID TO UPPER LEVEL FLOW
WILL SUPPORT INCREASINGLY SCATTERED CONVECTION IN THIS HIGH PW
AXIS, WITH LOCALLY HEAVY RAINS AND ISOLATED RUNOFF ISSUES.
..UPPER MS VALLEY/UPPER LAKES
CONVECTION EXPECTED TO BECOME INCREASINGLY ACTIVE LATE TUE
AFTERNOON INTO TUE NIGHT/EARLY HOURS OF WED ALONG AND AHEAD OF THE
SURFACE FRONT MOVING SLOWLY ACROSS THE UPPER MS VALLEY. FAVORABLE
RIGHT ENTRANCE REGION JET DYNAMICS AHEAD OF THIS FRONT IN AN AXIS
OF ABOVE AVERAGE PW VALUES WILL SUPPORT POTENTIAL FOR HEAVY RAINS
WITH ORGANIZED CONVECTION ALONG AND AHEAD OF THIS COLD FRONT WITH
ISOLATED RUNOFF ISSUES POSSIBLE.
ORAVEC
DAY 5
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL THE UPPER
MISSISSIPPI VALLEY/UPPER LAKES REGION AND ACROSS NORTHERN NY STATE
INTO NORTHERN NEW ENGLAND...
..NORTHERN NEW YORK STATE INTO NORTHERN NEW ENGLAND
SIMILAR TO THE DAY 4 TIME PERIOD, ADDITIONAL SHORTWAVE ENERGY IS
EXPECT TO RIDE ALONG THE TOP OF THE OHIO VALLEY CLOSED UPPER HIGH
ACROSS SOUTHEAST CANADA INTO NORTHERN NY STATE AND NEW ENGLAND
DURING DAY 5. THESE HEIGHT FALLS WILL BE ACCOMPANIED BY ANOTHER
AREA OF ANOMALOUS PW VALUES, 2 TO 3 STANDARD DEVIATIONS ABOVE THE
MEAN, PUSHING OUT OF SOUTHEAST ONTARIO AND SOUTHERN QB INTO
NORTHERN NY STATE AND NORTHERN NEW ENGLAND. WHILE THERE IS THE
TYPICAL AMOUNT OF SPREAD WITH QPF DETAILS, THERE IS A SIGNAL FOR
ADDITIONAL ORGANIZED CONVECTION MOVING IN A NORTHWEST TO SOUTHEAST
DIRECTION ACROSS NORTHERN NY STATE INTO NORTHERN NEW ENGLAND,
SUPPORTING HEAVY RAINS AND LOCALIZED RUNOFF ISSUES, ESPECIALLY IN
AREAS OF TRAINING.
..UPPER MS VALLEY/UPPER LAKES
ANOTHER ROUND OF SHORTWAVE ENERGY PUSHING NORTHEASTWARD FROM THE
CENTRAL PLAINS INTO THE UPPER MS VALLEY/UPPER LAKES REGION WILL
SUPPORT ANOTHER ROUND OF POTENTIALLY ORGANIZED FRONTAL/PRE-FRONTAL
CONVECTION LATE WEDNESDAY INTO EARLY THURSDAY ACROSS THESE REGIONS.
.THE GFS AND EC BOTH SHOW PW VALUES BECOMING ANOMALOUS IN THE
VICINITY OF THIS FRONT LATE WEDNESDAY INTO EARLY THURSDAY,
SUPPORTING HEAVY RAIN POTENTIAL AND ISOLATED RUNOFF ISSUES. THE
MARGINAL RISK WAS DRAWN TO ENCOMPASS THE TYPICAL AMOUNT OF SPREAD
IN THE GUIDANCE AT THIS TIME RANGE.
ORAVEC
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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