681
FXUS02 KWBC 160751
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 AM EDT TUE SEP 16 2025
VALID 12Z FRI SEP 19 2025 - 12Z TUE SEP 23 2025
..OVERVIEW
THE UPPER AIR PATTERN FRIDAY INTO THIS WEEKEND FEATURES A DEEP LOW
CENTERED OVER THE LABRADOR SEA WITH A TROUGH THAT DESCENDS OVER THE
NORTHEAST, FILLING/WEAKENING LOW PRESSURE TRACKING FROM THE
NORTHERN PLAINS TO THE UPPER MIDWEST, A TROUGH ALONG THE CALIFORNIA
COAST THAT WEAKENS/SHEDS A LOW OFFSHORE, WITH RIDGING IN BETWEEN
OVER THE MOUNTAIN WEST AND MIDWEST. POTENT TROUGHING IS THEN
FORECAST TO ENTER THE PACIFIC NORTHWEST SATURDAY NIGHT AND REACH
THE MIDWEST OR GREAT LAKES BY TUESDAY. WETTER THAN NORMAL
CONDITIONS CAN BE EXPECTED FRIDAY OVER THE GREAT PLAINS STATES,
SOUTH FLORIDA, AND CALIFORNIA INTO THE DESERT SOUTHWEST, AND THE
UPPER MIDWEST THIS WEEKEND. COOL AIR DAMMING IS LIKELY TO SPREAD
DOWN THE EASTERN SEABOARD INTO THE CAROLINA PIEDMONT SATURDAY AND
LINGER INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z GLOBAL DETERMINISTIC SUITE HAS COME INTO BETTER AGREEMENT
THAN THE PRIOR RUN FOR BOTH THE UPPER LOW OVER THE NORTHERN PLAINS
FRIDAY AND UPPER MIDWEST SATURDAY AND THE LOW THAT DEVELOPS OFF THE
CA COAST THIS WEEKEND. THE EC/GFS/CMC AGREE ON THE SATURDAY 00Z LOW
CENTER OVER THE DAKOTAS WHILE THE UKMET TRENDED NORTH INTO
MANITOBA. BY 12Z SUNDAY, THE EC/GFS ARE IN AGREEMENT WITH THE LOW
OVER THE MN/WI BORDER WHILE THE CMC/UKMET ARE SLOWER/FARTHER WEST.
IT IS WORTH NOTING THAT THE 00Z EC-AIFS IS NOTABLY FARTHER EAST,
REACHING THE L.P. OF MI BY 12Z SUNDAY. THE LOW THAT DEVELOPS AND
CUTS OFF WEST OF CA FRIDAY NIGHT IS IN DECENT AGREEMENT WITH THE
EC/GFS FOR NOT BEING TOO FAR OFFSHORE WHILE THE CMC/UKMET ARE
FARTHER WEST. THE GFS/EC RETAIN THE LOW CLOSER TO THE CENTRAL CA
COAST BY 00Z MONDAY WITH THE CMC/UKMET STILL FARTHER OFFSHORE.
THEN FOR THE TROUGH INTO THE NORTHWEST SATURDAY NIGHT, THE GFS
REMAINS THE MOST PROGRESSIVE. WHILE THE GFS/CMC BRING THE
TROUGH/LOW TO THE GREAT LAKES, THE 00Z EC NOW SHIFTS A STRONGER LOW
DOWN THE EASTERN SIDE OF THE GREAT PLAINS WHICH IS IN SOMEWHAT
AGREEMENT WITH RECENT EC-AIFS RUNS DEPICTING A TROUGH AXIS OVER MO
BY 12Z TUESDAY.
THE WPC BLEND FROM THE EVENING HEAVILY FAVORS THE 12Z EC/ECENS
THROUGH THE FORECAST RANGE WITH AN EMPHASIS ON THE CHARACTERISTICS
THAT LINED UP WITH THE 18Z EC-AIFS WHICH WERE GENERALLY NOT FOUND
IN THE 12Z CMC.
..WEATHER/HAZARDS HIGHLIGHTS
ENHANCED GULF MOISTURE CONTINUES TO SURGE UP THE PLAINS TO MEET
FRONTAL PATTERNS AHEAD OF THE OCCLUDING LOW PRESSURE SYSTEM OVER
THE UPPER MISSISSIPPI VALLEY FRIDAY AND THEN AT LEAST WISCONSIN ON
SATURDAY. THE DAY 4 MARGINAL RISK WAS TOUCHED UP A BIT BASED ON THE
00Z QPF CONSENSUS AND PW GRADIENT THAT FEATURES ANOMALIES AROUND +2
SIGMA. A DAY 5 MARGINAL RISK WAS RAISED FOR CENTRAL AND SOUTHERN
WISCONSIN BASED ON WHERE THE 00Z QPF CONSENSUS IS MOST ROBUST
DESPITE AN OVERALL WEAKENING TO THE LOW/FORCING EXPECTED.
REMNANT TROPICAL MOISTURE CONTINUES A SURGE INTO CALIFORNIA AND
EXPANSION EAST OVER THE DESERT SOUTHWEST FRIDAY AS THE UPPER RIDGE
AXIS OVER CA SHIFTS EAST TO THE INTERMOUNTAIN WEST AND TROUGHING
AMPLIFIES ALONG/OFF THE COAST. THE DAY 4 MARGINAL ERO IS MAINTAINED
FOR THE SIERRA NEVADA AND A LARGE NEW AREAS IS WARRANTED OVER THE
LOWER CO RIVER INTO NEVADA, EAST ACROSS SOUTHERN ARIZONA TO THE
SACRAMENTO MTNS OF NEW MEXICO GIVEN THE HIGH MOISTURE ANOMALIES OF
2 TO 3 SIGMA OVER SOUTHWEST AZ AND 1.5 INTO NM.
A STALLED FRONT OVER THE SOUTHERN FLORIDA PENINSULA CONTINUES TO
PROVIDE FOCUS FOR MUCH ABOVE NORMAL MOISTURE AND COMBINED WITH WET
ANTECEDENT CONDITIONS FRIDAY. A DAY 4 MARGINAL ERO IS INTRODUCED
FOR THE MIAMI METRO PER COORDINATION WITH WFO MFL.
AN UPPER RIDGE WILL PROMOTE HEAT OVER THE MIDWEST AND SOUTHEAST
FRIDAY INTO THE WEEKEND WITH MAX TEMP ANOMALIES OF 5-15 DEGREES
ABOVE NORMAL. A STRONG SURFACE HIGH CROSSING THE NORTHEAST SATURDAY
SHOULD SEND A DECENT COLD FRONT DOWN MUCH OF THE EASTERN SEABOARD
WITH COOL AIR DAMMING LINGERING EAST OF THE APPALACHIANS AND LIKELY
THROUGH THE CAROLINA PIEDMONT AT LEAST INTO MONDAY. BELOW NORMAL
TEMPERATURES FROM ONSHORE FLOW, CLOUDS, AND POSSIBLE RAIN CAN BE
EXPECTED.
JACKSON
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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