265
FOUS30 KWBC 130050
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
850 PM EDT FRI SEP 12 2025
DAY 1
VALID 01Z SAT SEP 13 2025 - 12Z SAT SEP 13 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NEW MEXICO & THE NORTHERN PLAINS...
..NEW MEXICO & COLORADO
A MERIDIONALLY-ORIENTED AXIS OF HEAVY RAINFALL HAS BEEN MOVING
SLOWLY EASTWARD THIS AFTERNOON INTO THIS EVENING WITHIN AN
ANOMALOUSLY MOIST AIRMASS WITH SUFFICIENT INSTABILITY. DUE TO RADAR
REFLECTIVITY TRENDS AND TRENDS IN THE 12Z REFS/18Z HREF, REDUCED
THE SIZE OF THE RISK AREAS, PARTICULARLY THE SLIGHT RISK TO COVER
PORTIONS OF SOUTHERN AND CENTRAL NM. ACTIVITY SHOULD FADE WITH TIME
AS CIN SETS IN AND INSTABILITY ERODES FURTHER.
..NORTHERN ROCKIES ONTO THE NORTHERN PLAINS
THE UPPER LOW CENTER SHIFTS NORTH TO MT BY LATE TONIGHT, AIDING IN
THE IMPORT AND PERSISTENCE OF ABOVE AVERAGE MOISTURE AND SUFFICIENT
EFFECTIVE BULK SHEAR ACROSS THE REGION. ISOLATED TO WIDELY
SCATTERED SHOWERS AND THUNDERSTORMS SHOULD PERSIST ACROSS MT, WITH
THE GREATEST THREAT OF ORGANIZED AND PERSISTENT CONVECTION AND
HEAVY RAINFALL REMAINING NEAR THE MT/SD/ND BORDER OVERNIGHT.
..FLORIDA
A STATIONARY FRONT PERSISTS OVER SOUTH FLORIDA. MOISTURE REMAINS
PLENTIFUL AND EFFECTIVE BULK SHEAR REMAINS ELEVATED, CONTINUING THE
POSSIBILITY OF ORGANIZED CONVECTION. THE RISK AREAS WERE
RESTRICTED TO THE SOUTHERNMOST PENINSULA WHERE DAYTIME
THUNDERSTORMS SHOULD LINGER FOR A COUPLE MORE HOURS AND FOR THE
POSSIBILITY OF SHORT TRAINING BANDS ALONG THE IMMEDIATE EAST COAST
WHERE SOME ONSHORE FLOW FROM OVER THE UNSTABLE GULF STREAM WATERS
COULD LEAD TO RANDOM SHORT, TRAINING BAND DEVELOPMENT.
..UPPER MIDWEST
ONGOING ACTIVITY OVER MN ARROWHEAD AND PORTIONS OF WI ARE EXPECTED
TO SLOWLY FADE OVERNIGHT. MAINTAINED THE MARGINAL RISK FOR THE
HEAVY RAIN POSSIBILITY OVER THE NEXT FEW HOURS, THOUGH THE GUIDANCE
DOES TRY TO FLARE SOME OVERNIGHT CONVECTION ONCE MORE ACROSS
NORTHERN WI. THE 12Z REFS/18Z HREF AND RADAR REFLECTIVITY TRENDS
WERE USED TO RESHAPE THE MARGINAL RISK AREA IN THIS REGION.
ROTH
DAY 2
VALID 12Z SAT SEP 13 2025 - 12Z SUN SEP 14 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE TEXAS AND
OKLAHOMA PANHANDLES INTO EAST NEW MEXICO AND FAR WESTERN TEXAS, AS
WELL AS FOR WESTERN NORTH DAKOTA...
..20Z UPDATE
SOME NOTABLE CHANGES FOR THIS UPDATE INCLUDE:
1) TRIMMING THE NORTHERN END OF THE INHERITED SLGT RISK, AS THE
MOST NOTABLE SIGNAL FOR CONVECTIVE ORGANIZATION AND POTENTIAL
TRAINING/REPEATING EXISTS FROM EASTERN NM INTO THE TX/OK PANHANDLES
(AS NOTED IN THE PREVIOUS DISCUSSION WITH THE ENHANCEMENT OF THE
LOW-LEVEL JET). THE MRGL WAS STILL MAINTAINED INTO THE CENTRAL HIGH
PLAINS, AND IN FACT WAS GENERALLY EXPANDED WESTWARD INTO MORE OF
THE CENTRAL/SOUTHERN ROCKIES AND INTERMOUNTAIN WEST AS ANOMALOUS
MOISTURE MAY BE SLOWER TO RETREAT THAN PRIOR GUIDANCE SUGGESTED
(BASED LARGELY ON THE NEW 12Z CAMS, AS WELL AS THE CHARACTER OF
CONVECTION TODAY BEING MORE IMPRESSIVE THAN MODELS INDICATED).
2) THE REMOVAL OF THE SLGT RISK OVER SOUTH FL, AS THE DECREASING
MOISTURE TREND NOTED BELOW IS STILL EVIDENT WITH A NOTABLE LOWERING
OF EXPECTED QPF BASED ON THE NEW 12Z CAMS (WHICH HAVE GENERALLY
BEEN TOO HOT IN THIS PATTERN WITH CONVECTION OVER SOUTH FL TO BEGIN
WITH). THE MRGL RISK WAS MAINTAINED FOR ANY LINGERING EXCESSIVE
RAINFALL THREAT (AND MAY WELL BE ABLE TO BE REMOVED EARLY TOMORROW).
3) INTRODUCTION OF A MRGL RISK FOR CHICAGOLAND AND SURROUNDINGS
(SOUTHEAST WI, NORTHEAST IL, MUCH OF IN, AND FAR SOUTHWEST MI).
WHILE THE THREAT FOR LOCALIZED FLASH FLOODING IS CONDITIONAL, THERE
IS A NOTABLE SIGNAL FROM THE 12Z CAMS SUGGESTING THE POTENTIAL FOR
3" EXCEEDANCE (12Z HREF 3" EXCEEDANCE PROBS OF 20-30%) WITH BOTH
THE ARW AND ARW2 SHOWING POTENTIAL FOR TRAINING HEAVY RAINFALL (AS
WELL AS THE NAM-NEST, WHICH IS THE HEAVIEST OUTLIER).
OTHERWISE, ADJUSTED THE SLGT/MRGL BORDERS FOR THE NORTHERN PLAINS
BASED ON THE NEW GUIDANCE.
CHURCHILL
..PREVIOUS DISCUSSION
..CENTRAL HIGH PLAINS THROUGH SOUTHERN ROCKIES
THE UPPER LEVEL TROUGH OVER THE INTERMOUNTAIN WEST BECOMES
NEGATIVELY TILTED ON SATURDAY WITH THE MONSOONAL MOISTURE AXIS OVER
NM DURING THE DAY SHIFTING TO THE SOUTHERN HIGH PLAINS OVERNIGHT.
THE POSITION OF THIS TROUGH WILL ENHANCE THE LOW LEVEL JET ON THE
HIGH PLAINS SATURDAY NIGHT AND DRAW DEEPER GULF MOISTURE NORTH
OVER THE PANHANDLES AND EASTERN NEW MEXICO AND THROUGH WESTERN
KANSAS. THIS WILL ENCOURAGE DIURNALLY DEVELOPING LINES OF STORMS
FROM NEW MEXICO TERRAIN TO PRESS EASTWARD ONTO THE HIGH PLAINS.
GIVEN THE +2 SIGMA PW ANOMALIES AND OVERALL SLOW STORM MOTION, THE
SLIGHT RISK AREA WAS EXPANDED A BIT OVER WESTERN KS AND DOWN INTO
FAR WESTERN TEXAS.
..SOUTH FLORIDA
THE FRONT WILL PUSH SOUTH FROM FLORIDA DURING THE DAY SATURDAY WITH
ANOMALOUS MOISTURE LINGERING IN THE MORNING OVER THE MIAMI METRO
WHERE A SLIGHT RISK PERSISTS. THE SLIGHT RISK STILL LOOKS GENEROUS
GIVEN THE DECREASING MOISTURE PROFILE THROUGH THE DAY, BUT IS
MAINTAINED FOR NOW.
..NORTHERN PLAINS
THE UPPER LOW CENTER OVER CENTRAL MT WILL ALLOW THE FOCUS FOR
HEAVY CONVECTION TO SHIFT NORTH A BIT FROM FRIDAY WITH BOTH MORNING
AND DIURNAL MAX ACTIVITY LOOKING TO FOCUS ON WESTERN ND. GIVEN GOOD
OVERLAP IN HEAVIER PRECIP AMONG AVAILABLE CAMS AND THE EC-AIFS, A
SLIGHT RISK IS RAISED OVER WESTERN ND. PIVOTING OF THE LOW WITHOUT
MUCH LATERAL MOVEMENT IS EXPECTED, PROLONGED HEAVY RAINFALL IS
POSSIBLE WITH.
JACKSON
DAY 3
VALID 12Z SUN SEP 14 2025 - 12Z MON SEP 15 2025
..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE DAKOTAS
..20Z UPDATE
ONLY MINOR ADJUSTMENTS WERE NECESSARY BASED ON THE NEW 12Z MODEL
SUITE, AS THE BULK OF THE GUIDANCE ARE IN GOOD AGREEMENT ON THE
AXIS OF HIGHEST QPF.
CHURCHILL
..PREVIOUS DISCUSSION
..CENTRAL AND NORTHERN PLAINS
NEGATIVELY-TILTED TROUGH AXIS LIFTING UP THE CENTRAL PLAINS SUNDAY
SHOULD PROVIDE A NARROW FOCUS TO CONVECTIVE DEVELOPMENT OVER THE
WESTERN OR CENTRAL DAKOTAS. THIS ACTIVITY WILL BE HEAVY GIVEN PW
ANOMALIES OF +3 SIGMA PERSIST OVER THIS AREA. FURTHER DEVELOPMENT
IS EXPECTED FROM CENTRAL KS UP THROUGH THE DAKOTAS WHERE A GENEROUS
MARGINAL RISK REMAINS IN EFFECT.
JACKSON
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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