599
FXUS02 KWNH 170752
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 AM EDT THU SEP 17 2026
VALID 12Z SAT SEP 19 2026 - 12Z WED SEP 23 2026
...HEAVY RAINFALL THREATENS THE LOWER MISSOURI VALLEY AND
NORTHEAST, WHILE MONSOON STORMS REIGNITE OVER THE SOUTHERN HIGH
PLAINS/ROCKIES...
..OVERVIEW
A TROUGH PROPAGATING ACROSS THE NORTHERN TIER MAY PRODUCE HEAVY
RAINFALL OVER PORTIONS OF THE NORTHERN PLAINS, LOWER MISSOURI
VALLEY AND INTO THE NORTHEAST THIS WEEKEND. A RIDGE IN THE
SOUTHEAST WILL EXPAND INTO THE THE SOUTH-CENTRAL U.S. WHILE AN EAST
PACIFIC TROUGH ENTERS THE WEST COAST. THIS WILL REIGNITE MONSOON
STORMS OVER MUCH OF NEW MEXICO AND THE TEXAS PANHANDLE BEGINNING ON
TUESDAY. PERSISTENT DIFFLUENCE WILL LIKELY SUPPORT SHOWERS AND
THUNDERSTORMS IN THE MID-ATLANTIC NEXT WEEK, WHILE A WEAK
DISTURBANCE LINGERING AROUND THE FLORIDA PENINSULA WILL BE
RESPONSIBLE FOR DAILY HEAVY RAINFALL POTENTIAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODELS ARE IN REASONABLY GOOD AGREEMENT ON THE
EVOLUTION OF THE MID-LEVEL HEIGHT PATTERN ACROSS THE LOWER 48
DURING THE MEDIUM RANGE PERIOD. THERE'S SOME UNCERTAINTY AROUND THE
LOCATION OF THE WEST COAST TROUGH ON DAYS 6 AND 7, WITH SOME MODELS
SUGGESTING THAT IT BECOMES A CUT-OFF LOW AND SOME PHASING IT BACK
INTO THE DIGGING PARENT TROUGH CENTERED OFF THE BC COAST.
THE EURO SUITE IS FAVORED THROUGHOUT THE MEDIUM RANGE, WITH SOME
UKMET INVOLVEMENT THROUGH DAY 4. THE ENSEMBLE MEANS ARE INTRODUCED
TO THE BLEND ON DAY 5 AND INCREASED IN WEIGHTING THROUGH DAY 7. THE
EXACT EVOLUTION OF A SURFACE COLD FRONT PUSHING SOUTH THROUGH THE
EAST COAST NEXT WEEK IS ALSO UNCERTAIN.
..WEATHER/HAZARDS HIGHLIGHTS
A LOW PRESSURE SYSTEM WITH ATTENDANT SURFACE FRONTS DRAPED ACROSS
THE CENTRAL U.S., MIDWEST AND EAST COAST WILL ACT AS A FOCUS FOR
SCATTERED SHOWERS AND THUNDERSTORMS OVER THE NORTHERN/CENTRAL
PLAINS AND NORTHEAST ON SUNDAY. THERE'S A SLIGHT RISK (AT LEAST 15%
CHANCE) OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHEASTERN KANSAS
INTO NORTHERN MISSOURI AND WESTERN ILLINOIS, WITH A MORE ISOLATED
FLASH FLOOD THREAT OVER PORTIONS OF THE OHIO VALLEY, NORTHEAST AND
MID-ATLANTIC ON SUNDAY. SHOWERS AND THUNDERSTORMS DRIFT SOUTH ALONG
WITH THE ASSOCIATED COLD FRONT ON MONDAY. ISOLATED FLASH FLOODING
WILL BE POSSIBLE FOR THE MID-ATLANTIC ON TUESDAY THEN THE SOUTHEAST
COAST BY MID-WEEK.
ELSEWHERE, A WEST COAST TROUGH AND RETROGRADING SOUTHERN U.S. RIDGE
WILL CREATE A CORRIDOR FOR MONSOON MOISTURE TO LIFT NORTH THROUGH
BEGINNING ON MONDAY. STORMS SHOULD PROLIFERATE ACROSS NEW MEXICO
AND THE TEXAS PANHANDLE BEGINNING ON TUESDAY AND CONTINUING THROUGH
THE REST OF THE WEEK. ISOLATED TO SCATTERED FLASH FLOODING CAN BE
EXPECTED FOR THOSE AREAS. BURN SCARS IN THE SANGRE DE CRISTO AND
SACRAMENTO MOUNTAINS, AS WELL AS SLOT CANYONS, DRY WASHES, AND
RECENTLY SATURATED SOILS WILL BE ESPECIALLY SUSCEPTIBLE TO FLASH
FLOODING FROM NEXT WEEK'S ROUNDS OF MONSOON STORMS.
KEBEDE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page