484
FXUS02 KWBC 161917
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
317 PM EDT WED SEP 16 2026
VALID 12Z SAT SEP 19 2026 - 12Z WED SEP 23 2026
...HEAVY RAINFALL THREATS FOR THE UPPER GREAT LAKES AND NORTHERN
HIGH PLAINS THIS WEEKEND, WITH MONSOONAL MOISTURE INCREASING AGAIN
NEXT WEEK FOR THE SOUTHWEST...
..OVERVIEW
A TROUGH WILL PRODUCE HEAVY RAINFALL ACROSS PORTIONS OF THE UPPER
MIDWEST/GREAT LAKES AND POTENTIALLY THE NORTHEAST THIS WEEKEND.
MEANWHILE, THE PASSAGE OF A CENTRAL U.S. TROUGH WILL BRING HEAVY
RAINFALL CONCERNS TO PARTS OF MONTANA BUT SHOULD ALSO REDUCE THE
THREAT OVER THE SOUTHWEST AND SOUTHERN PLAINS/ROCKIES THIS WEEKEND.
AN EAST PACIFIC DISTURBANCE LOOKS TO RENEW MONSOONAL STORMS ACROSS
THE REGION EARLY NEXT WEEK. A MID- LEVEL DISTURBANCE MEANDERING
AROUND THE FLORIDA PENINSULA SHOULD GENERATE MULTIPLE DAYS OF WET
WEATHER ACROSS SOUTHERN FLORIDA BEGINNING THIS WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE REMAINS IN RELATIVELY GOOD AGREEMENT ON THE
EVOLUTION OF THE PATTERN DURING THE MEDIUM RANGE PERIOD. THERE ARE
LINGERING UNCERTAINTIES/DIFFERENCES WITH VARIOUS SYSTEMS, BUT THESE
SEEM WELL WITHIN THE REALM OF POSSIBILITIES WITH NO TRUE OUTLIER
SOLUTIONS. EVEN SMALL DIFFERENCES THOUGH POSE IMPACTS TO SENSIBLE
WEATHER, ESPECIALLY ACROSS FLORIDA AS A BROAD UPPER DISTURBANCE
SHIFTS ACROSS THE STATE. THE SECOND TROUGH INTO THE SOUTHWEST NEXT
WEEK ALSO SHOWS SOME NOTABLE DIFFERENCES AND THUS IMPACTS ON HEAVY
RAINFALL POTENTIAL ACROSS THIS REGION.
A GENERAL MODEL BLEND SERVED AS A GOOD STARTING POINT FOR THE
EARLY HALF OF THE FORECAST PERIOD. TRENDED MORE TOWARDS THE ECMWF
AND EC-AIFS SOLUTIONS LATE PERIOD AS THEY WERE CLOSER TO THE
ENSEMBLE MEANS AMIDST GROWING UNCERTAINTY IN THE DETAILS AND TIMING
OF INDIVIDUAL SYSTEMS. THE ENSEMBLE MEANS MADE UP 60 PERCENT OF
THE BLEND BY DAY 7, HELPING TO MAINTAIN OVERALL CONSISTENCY WITH
THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A LOW PRESSURE SYSTEM WILL BRING ROUNDS OF THUNDERSTORMS AND HEAVY
RAINFALL TO PORTIONS OF THE NORTH-CENTRAL U.S. LATER THIS WEEK.
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO SPREAD INTO
PARTS OF THE UPPER MIDWEST/GREAT LAKES, WHERE A SLIGHT RISK (AT
LEAST 15 PERCENT CHANCE) OF EXCESSIVE RAINFALL IS IN EFFECT ON
SATURDAY. THUNDERSTORMS AND HEAVY RAINFALL FOCUS SHOULD EXPAND INTO
THE OHIO VALLEY AND NORTHEAST ON SUNDAY, BEFORE DROPPING SOUTH
INTO THE MID-ATLANTIC BY EARLY NEXT WEEK.
A COMPACT CLOSED LOW/UPPER SHORTWAVE WILL SHIFT INTO THE NORTH-
CENTRAL U.S. THIS WEEKEND BRINGING A THREAT FOR HEAVY RAINFALL
ACROSS PARTS OF THE NORTHERN HIGH PLAINS ON SATURDAY. SHOWERS WILL
CONTINUE ALONG AND AHEAD OF THE SURFACE FRONT AS IT SHIFTS INTO THE
CENTRAL AND SOUTHERN PLAINS. THIS TROUGH WILL ALSO WEAKEN THE
SOUTHERN U.S. RIDGE, PROVIDING A BREAK IN THE MONSOONAL MOISTURE
ACROSS THE SOUTHWEST. THIS MAY BE SHORT LIVED THOUGH AS ANOTHER
TROUGH INTO SOUTHERN CALIFORNIA EARLY NEXT WEEK RENEWS MOISTURE
WITH A HEAVY RAINFALL THREAT. SLOT CANYONS AND DRY WASHES ARE
ESPECIALLY SUSCEPTIBLE TO FLASH FLOODING FROM ANY STORMS THAT
DEVELOP.
THE PERSISTENT AND ANOMALOUS RIDGE OVER THE SOUTH WILL BREAK DOWN
THIS WEEKEND, WITH TEMPERATURES BEGINNING TO MODERATE ACROSS MANY
AREAS BY LATER IN THE WEEKEND AND ESPECIALLY EARLY NEXT WEEK.
HAZARDOUS HEAT THREATS MAY PERSIST IN SOME PARTS OF THE SOUTH-
CENTRAL U.S., BUT SHOULD NOT BE NEARLY AS WIDESPREAD AS IT IS THIS
WEEK.
SANTORELLI/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
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