265
FXUS02 KWBC 170810
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
410 AM EDT FRI OCT 17 2025
VALID 12Z MON OCT 20 2025 - 12Z FRI OCT 24 2025
..OVERVIEW
A COUPLE OF PROGRESSIVE UPPER TROUGHS ARE FORECAST TO MOVE THROUGH
THE EASTERN TWO-THIRDS OF THE COUNTRY THROUGH THE MEDIUM RANGE
PERIOD, WITH A TENDENCY FOR THEM TO CLOSE OFF INTO UPPER LOWS AS
THEY NEAR THE NEW ENGLAND COAST. MEANWHILE, AN UPPER LOW IS
FORECAST TO PUSH ONSHORE INTO THE SOUTHWEST AMID GENERAL RIDGING
ACROSS THE NORTHWEST BEFORE RIDGING TAKES OVER LATE NEXT WEEK WHILE
PROGRESSING EAST INTO THE NORTHERN HIGH PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE SHOWS REASONABLY GOOD AGREEMENT ON THE
AFOREMENTIONED SYNOPTIC SCALE PATTERN THROUGH THE MEDIUM RANGE
PERIOD. THERE HAS BEEN A CONTINUED TENDENCY FOR THE MODELS TO
HASTEN THE EASTWARD PROGRESSION OF BOTH TROUGHS, AND FOR THEM TO
CLOSE OFF AS THEY NEAR THE NEW ENGLAND COAST. MEANWHILE, THE EC
MEAN HAS BEEN MOST CONSISTENT IN DEPICTING AN UPPER RIDGE
AMPLIFYING TOWARD THE END OF NEXT WEEK ACROSS THE NORTHERN ROCKIES
TO NORTHERN HIGH PLAINS. FOR THE UPPER LOW THAT IS FORECAST TO MOVE
INTO THE SOUTHWEST MIDWEEK NEXT WEEK, THE EC MEAN IS SHOWING A
FASTER TREND FOR THE LOW TO MOVE INLAND AND TO OPEN UP THE LOW
EARLIER. IN CONTRAST, THE GEFS AND CMC MEAN ARE TRENDING SLOWER
WITH THE FORWARD MOTION OF THE LOW WHILE DELAYING THE ONSET OF
OPENING UP THE LOW INTO A TROUGH.
THE WPC MEDIUM RANGE FORECAST PACKAGE WAS BASED ON A COMPOSITE
BLEND OF THE 18Z GFS/GEFS, WITH THE 12Z EC/EC MEAN TOGETHER WITH
THE 12Z CMC/CMCE, WITH INCREASING WEIGHTING TOWARD THE
EPS/GEFS/CMCE CONSENSUS ON DAY 7. THIS BLEND SHOWED GOOD CONTINUITY
WITH THE PREVIOUS WPC FORECASTS WITH THE FASTER EASTWARD MOTION OF
THE TROUGHS AS NOTED ABOVE.
..WEATHER/HAZARDS HIGHLIGHTS
THE MEDIUM RANGE PERIOD SHOULD BEGIN WITH MODERATE TO LOCALLY HEAVY
RAIN POSSIBLY WITH EMBEDDED THUNDERSTORMS ACROSS NORTHERN NEW
ENGLAND AHEAD OF THE FIRST TROUGH THAT COULD DEVELOP INTO A CLOSED
LOW. A MARGINAL RISK OF FLASH FLOODING HAS BEEN MAINTAINED FOR THIS
AREA. MEANWHILE, ANOTHER UPPER TROUGH MAY DEVELOP INTO A CLOSED
LOW OVER THE GREAT LAKES ON TUESDAY BUT WITH MODEST AMOUNTS OF
RAINFALL.
OUT WEST, INCREASING CHANCE OF MODERATE TO HEAVY PRECIPITATION IS
SEEN NEAR THE PACIFIC NORTHWEST COAST TOWARD THE END OF NEXT WEEK
AHEAD OF AN APPROACHING UPPER TROUGH. MEANWHILE, THERE ARE
INCREASING MODEL SIGNALS FOR AN EXPANDING AREA OF RAIN ACROSS THE
MID-SOUTH LATER NEXT WEEK BUT WITH A FAIR AMOUNT OF UNCERTAINTY IN
THE AMOUNTS AND PLACEMENT AT THIS POINT IN TIME.
KONG
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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