344
FXUS02 KWBC 011910
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 PM EDT WED OCT 1 2025
VALID 12Z SAT OCT 04 2025 - 12Z WED OCT 08 2025
..OVERVIEW
AN AMPLIFIED UPPER FLOW PATTERN IS EXPECTED FOR THIS FORECAST
PERIOD WITH A LARGE TROUGH OVER THE WESTERN U.S. AND A RIDGE OVER
THE EAST-CENTRAL STATES. THE UPPER TROUGH IS LIKELY TO EVOLVE INTO
A CUT-OFF LOW BY EARLY NEXT WEEK ACROSS CALIFORNIA AND NEVADA,
WHILE THE EAST COAST RIDGE AMPLIFIES. TROPICAL MOISTURE
INTERACTING WITH A STATIONARY FRONT COULD DELIVER HEAVY RAIN AND
THUNDERSTORMS ALONG THE EAST COAST OF FLORIDA AND ALONG PORTIONS OF
THE CENTRAL GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE FEATURES GOOD OVERALL SYNOPTIC SCALE
AGREEMENT THROUGH THE UPCOMING WEEKEND, WITH A GENERAL
DETERMINISTIC MODEL COMPROMISE USED FOR FRONTS/PRESSURES. THE UKMET
IS SLIGHTLY FASTER WITH THE LARGE SHORTWAVE TROUGH OVER THE FOUR
CORNERS REGION, AND RECENT RUNS OF THE GFS HAVE BEEN FASTER WITH
THE PASSAGE OF THE COLD FRONT ACROSS EASTERN CANADA AND THE GREAT
LAKES REGION EARLY NEXT WEEK. THE AIFS GUIDANCE GENERALLY HAS A
BROADER UPPER TROUGH SITUATED OVER THE GREAT LAKES AND SOUTHERN
CANADA BY WEDNESDAY, WHEREAS THE OPERATIONAL GUIDANCE FAVORS MORE
OF A SHARPER TROUGH. THE ENSEMBLE MEANS WERE GRADUALLY INCREASED TO
ABOUT 40% BY NEXT WEDNESDAY AS MESOSCALE DIFFERENCES INCREASED.
..WEATHER/HAZARDS HIGHLIGHTS
PORTIONS OF THE GULF COAST AND SOUTHEAST COAST WILL REMAIN IN AN
ACTIVE, WET PATTERN AS TROPICAL MOISTURE INTERACTS WITH A
STATIONARY FRONTAL BOUNDARY. A COUPLE OF WEAK LOW PRESSURE CENTERS
MAY FORM ON THE FRONT AND COULD LIFT NORTH TO ENHANCE RAINFALL
NEAR THE CENTRAL GULF COAST, AND FROM THE EAST COAST OF FLORIDA UP
INTO THE GEORGIA COAST OVER THE WEEKEND. A MARGINAL RISK OF
EXCESSIVE RAINFALL WAS MAINTAINED FOR DAY 4 AND AND RAISED FOR DAY
5 ALONG THE EASTERN COAST OF FLORIDA AS URBAN AREAS TEND TO BE MORE
SENSITIVE, AND AN EVENTUAL SLIGHT RISK AREA COULD BE NEEDED AS THE
EVENT GETS CLOSER IN TIME. ADDITIONALLY, A DAY 4 MARGINAL WAS
RAISED FOR SOUTHEAST LOUISIANA WHERE HEAVY SHOWERS AND THUNDERSTORMS
ARE EXPECTED ALONG THE COASTLINE AND POINTS INLAND IN FAR
SOUTHEAST REACHES OF THE STATE. LOCALLY, 3 TO 4 INCHES OF RAIN WILL
BE POSSIBLE AND MAY LEAD TO ISOLATED AREAS OF FLOODING. A NEW DAY
5 MARGINAL RISK WAS ALSO ADDED FOR THE CENTRAL GULF COAST TO
ACCOUNT FOR THIS.
MULTIPLE ROUNDS OF PRECIPITATION IS FORECAST FOR THE WEST AND
INTERMOUNTAIN WEST AS SHORTWAVES WITHIN THE WESTERN U.S. UPPER-
TROUGH AND ASSOCIATED SURFACE FRONTS TRACK EASTWARD, ESPECIALLY FOR
THE ROCKIES AND INTERMOUNTAIN WEST. THE HIGHER ELEVATIONS CAN
EXPECT SNOW WITH THE PASSAGE OF THE UPPER TROUGH. MOISTURE LEVELS
WILL BE ABOVE NORMAL, AND EVEN THOUGH INSTABILITY WILL NOT BE ALL
THAT HIGH, AREAL QPF OF 1-2 INCHES ON SATURDAY COULD BE ENOUGH TO
LEAD TO SOME INSTANCES OF MINOR FLOODING IN POOR DRAINAGE AREAS,
AND THEREFORE A MARGINAL RISK AREA HAS BEEN INTRODUCED FOR THE DAY
4 PERIOD FROM THE LOWER ELEVATIONS OF NORTHERN WYOMING AND SOUTHERN
MONTANA, EASTWARD TO THE CENTRAL DAKOTAS. THE PACIFIC NORTHWEST
COULD SEE PRECIPITATION. RAIN CHANCES ARE FORECAST TO EXPAND INTO
THE NORTH- CENTRAL U.S. LATE WEEK INTO THE WEEKEND AS A COUPLE OF
FRONTAL SYSTEMS EMERGE INTO THE PLAINS.
SUMMER-LIKE TEMPERATURES WILL HOLD ON ACROSS MUCH OF THE CENTRAL
U.S. UNDER THE DEEP-LAYER RIDGE. EACH DAY THE MAXIMUM TEMPERATURES
WILL AVERAGE 15 TO 25 DEGREES ABOVE NORMAL THROUGH LATE WEEK, WELL
INTO THE 80S EVEN TO THE CANADIAN BORDER WHERE DAILY RECORD HIGH
TEMPERATURES WILL MOST LIKELY BE CHALLENGED OR BROKEN SATURDAY
AFTERNOON. FOR THE DESERT SOUTHWEST AND TEXAS, 90S ARE LIKELY TO
CONTINUE FOR EARLY OCTOBER. BY THE WEEKEND, WARMER THAN AVERAGE
TEMPERATURES COULD SHIFT A BIT EAST AND COVER THE GREAT LAKES
REGION AND NORTHEAST, WHILE THE NORTHERN PLAINS COOLS. MEANWHILE,
BELOW NORMAL TEMPERATURES ESPECIALLY FOR HIGHS ARE LIKELY ACROSS
THE WEST DUE TO UPPER TROUGHING AND RAINY/CLOUDY CONDITIONS.
HAMRICK/CAMPBELL
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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