355
FOUS30 KWBC 291546
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1146 AM EDT WED OCT 29 2025
DAY 1
VALID 16Z WED OCT 29 2025 - 12Z THU OCT 30 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN AND CENTRAL APPALACHIANS AND SURROUNDING PORTIONS OF THE
OHIO/TENNESSEE VALLEYS...
16Z UPDATE: MAIN CHANGE WAS REMOVAL OF THE VALLEY AREAS OF EASTERN
TN WHERE AN AREAL MIN IN QPF IS FORECAST ACROSS ALL GUIDANCE
LEADING TO LIMITED FLASH FLOOD CONCERNS. REMAINDER OF THE FORECAST
IS ON TRACK WITH THE PRIMARY MAXIMA STILL SITUATED IN THE CENTRAL
AND SOUTHERN APPALACHIANS AND NEIGHBORING BLUE RIDGE IN VA.
NEIGHBORHOOD PROBS FROM THE LATEST 12Z HREF WERE INDICATIVE OF SOME
>3" MAXIMA SITUATED OVER THE NORTHERN NECK OF VA WITH
PROBABILITIES UPTICK TO 25-50% IN-OF THE BLUE RIDGE EXTENSION JUST
EAST OF I-81. THIS MAKES SENSE SYNOPTICALLY WITH THE INCREASING
UPSLOPE COMPONENT INITIATING OVERNIGHT INTO THE END OF THE PERIOD
WITH A MODEST INSTABILITY REGIME DEVELOPING ALONG THE TERRAIN AND
POINTS EAST THANKS TO THE PROJECTED THETA_E ADVECTION PATTERN
MATERIALIZING AS THE ULL PIVOTS EASTWARD AND WE RESIDE IN
PERSISTENT ONSHORE FETCH FROM THE ATLANTIC. THANKS TO DRY
ANTECEDENT CONDITIONS LEADING INTO THE PERIOD, THE SETUP IS CURBED
TO BE MORE IN LINE WITH A MRGL RISK THRESHOLD, THUS MAINTAINED
GENERAL CONTINUITY OUTSIDE THE SMALL CHANGE IN TN AND THE WESTERN
FRINGES OF THE RISK AREA ACROSS CENTRAL TN AND KY.
KLEEBAUER
..PREVIOUS DISCUSSION..
RAINFALL IS EXPECTED TO OVERSPREAD THE TENNESSEE/OHIO VALLEY WITH
ANOMALOUS LOW- LEVEL MOISTURE TRANSPORT DRIVING EAST-SOUTHEAST
MOISTURE TRANSPORT INTO THE SOUTHERN/CENTRAL APPALACHIANS AS A
CLOSED UPPER LOW SWIVELS FROM THE MID-SOUTH TO THE OHIO VALLEY. HREF
NEIGHBORHOOD PROBS FOR >2" ARE RELATIVELY HIGH IN-OF THE BLUE
RIDGE FROM VIRGINIA DOWN INTO THE WESTERN CAROLINAS (60-90%) WITH A
VAST MAJORITY OF THE RAIN COMING FROM SHALLOW CONVECTIVE PROCESSES
FOCUSED WITHIN THE TERRAIN. LARGE SCALE FORCING ACROSS THE
AFOREMENTIONED AREAS WILL BE THE PRIMARY DRIVER FOR THE HEAVY RAIN
SCENARIO, HOWEVER A TONGUE OF ELEVATED THETA_E IS EXPECTED TO
ADVECT OFF THE ATLANTIC INTO THE CENTRAL APPS/BLUE RIDGE LEADING TO
A GREATER POTENTIAL FOR THAT LOW- TOPPED CONVECTION TO IMPACT
THESE ZONES. A MARGINAL RISK AREA REMAINS IN EFFECT FOR THIS PART
OF THE NATION.
CAMPBELL/KLEEBAUER
DAY 2
VALID 12Z THU OCT 30 2025 - 12Z FRI OCT 31 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
SOUTHERN PORTION OF THE NORTHEAST...
THIS SYSTEM IS FORECAST TO TRACK TO THE NORTHEAST AS THE
ASSOCIATED SURFACE LOW STRENGTHENS OVER THE MID-ATLANTIC ONWARD TO
THE NORTHEAST. HEAVY RAIN WILL ACCOMPANY THE LOW AND OVERSPREAD THE
REGION. THE BEST THREAT FOR CONVECTIVE ENHANCEMENT LEADING TO
BETTER RATES >1"/HR AND SOME MINOR TRAINING OFF STEADY SOUTHEAST
FLOW OFF THE ATLANTIC WILL OCCUR FROM SOUTHEAST PENNSYLVANIA UP
THROUGH NEW JERSEY, NEW YORK CITY METRO, AND WESTERN LONG ISLAND
TO ABOUT THE I-95 CORRIDOR IN CONNECTICUT. A MARGINAL RISK FOR
EXCESSIVE RAINFALL AND ISOLATED FLASH FLOOD CONCERNS IN THAT
URBANIZED CORRIDOR OF THE NORTHEASTERN U.S. REMAINS FOR THIS
PERIOD.
CAMPBELL/KLEEBAUER
DAY 3
VALID 12Z FRI OCT 31 2025 - 12Z SAT NOV 01 2025
...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN
WASHINGTON...
HEAVY PRECIPITATION IS LIKELY FRIDAY INTO SATURDAY FOR PORTIONS OF
THE PACIFIC NORTHWEST AS A MODERATELY STRONG ATMOSPHERIC RIVER
STREAMS ONSHORE AHEAD OF A LARGER NORTHEAST PACIFIC LOW. AREAL
AVERAGES OF 1 TO 3 INCHES WILL BE COMMON WITH THE POTENTIAL FOR
LOCAL MAXIMUMS OF 4+ INCHES. A MARGINAL RISK FOR EXCESSIVE RAINFALL
AND ISOLATED FLASH FLOODING CONCERNS IS IN EFFECT FOR WESTERN
WASHINGTON. MOST PRECIPITATION IS FORECAST TO STAY RAIN OTHER
THAN SNOW EVEN IN THE HIGHEST PEAKS OF THE OLYMPICS THROUGH FRIDAY,
WITH MORE SNOW IN THE CASCADES.
CAMPBELL
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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