842
FXUS02 KWNH 200756
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
355 AM EDT MON OCT 20 2025
VALID 12Z THU OCT 23 2025 - 12Z MON OCT 27 2025
..GENERAL OVERVIEW
THE LARGE SYNOPTIC SCALE TROUGH THAT WILL BE IN PLACE ACROSS THE
GREAT LAKES AND NORTHEAST THROUGH MID-WEEK IS FORECAST TO LIFT OUT
TO THE NORTH BY FRIDAY. A SOUTHERN STREAM SHORTWAVE CROSSING FROM
THE ROCKIES TO THE CENTRAL/SOUTHERN PLAINS WILL SUPPORT A SURFACE
LOW AND WARM FRONT FROM KANSAS TO THE ARKLATEX REGION, WITH
INCREASING SHOWERS AND STORMS. OUT WEST, A PATTERN CHANGE WILL TAKE
PLACE GOING INTO THE WEEKEND AS AN UPPER TROUGH AMPLIFIES OVER THE
REGION AND LEADS TO COLDER WEATHER AND MORE MOUNTAIN SNOW. THIS
SAME TROUGH IS EXPECTED TO SPUR SURFACE CYCLOGENESIS OVER THE
CENTRAL/NORTHERN PLAINS BY NEXT MONDAY WITH ADDITIONAL SHOWERS AND
STORMS EXPECTED.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE IS IN GOOD OVERALL AGREEMENT ACROSS
THE CONTINENTAL U.S. FOR THE BEGINNING OF THE PERIOD THURSDAY, AND
THIS ALSO HOLDS TRUE GOING INTO FRIDAY, WITH MAINLY MINOR MESOSCALE
DIFFERENCES, SO A MULTI-DETERMINISTIC MODEL BLEND WAS USED THROUGH
FRIDAY NIGHT. THE UKMET BECOMES MUCH STRONGER WITH A SURFACE LOW
APPROACHING THE PACIFIC NORTHWEST SATURDAY NIGHT COMPARED TO THE
OTHER GUIDANCE. BY NEXT MONDAY, THE CMC LIFTS THE MAIN TROUGH AXIS
ACROSS THE WESTERN U.S. FARTHER TO THE NORTH WITH MORE ZONAL FLOW
ALOFT FROM THE WEST COAST TO THE ROCKIES, WHEREAS THE MODEL
CONSENSUS SUGGESTS STRONGER TROUGHING. IN TERMS OF QPF, THE WPC
FORECAST WAS A LITTLE LIGHTER THAN THE NBM ACROSS EASTERN TEXAS
INTO MISSISSIPPI, AND ALSO LIGHTER ACROSS THE WEST COAST. THERE WAS
A TREND TO LIGHTER QPF COMPARED TO THE PREVIOUS FORECAST ACROSS THE
SOUTHEASTERN STATES AND HIGHER OVER THE CENTRAL PLAINS. THE
ENSEMBLE MEANS WERE INCREASED TO ABOUT HALF BY NEXT MONDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE SURFACE LOW THAT IS FORECAST TO EVOLVE OVER KANSAS AND OKLAHOMA
LATER THIS WEEK, ALONG WITH STRONG WARM AIR ADVECTION AND
INCREASING INSTABILITY, WILL LIKELY FUEL THE DEVELOPMENT OF
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS, PERHAPS IN THE
FORM OF A MESOSCALE CONVECTIVE SYSTEM. THERE WILL LIKELY BE PATCHY
QPF MAXIMA ON THE ORDER OF 1 TO 3 INCHES FROM EASTERN KANSAS TO THE
ARKLATEX REGION THROUGH FRIDAY, AND HIGHER RAINFALL RATES WITH THE
STORMS THE DEVELOP COULD LEAD TO SOME INSTANCES OF FLASH FLOODING,
SO THEREFORE A MARGINAL RISK IS VALID FOR BOTH THURSDAY AND FRIDAY
ACROSS THIS REGION. RAIN AND MOUNTAIN SNOW ALSO INCREASES FROM
NORTHERN CALIFORNIA TO WESTERN WASHINGTON LATE THURSDAY AND EVEN
MORE SO FOR FRIDAY, AND A MARGINAL RISK OF EXCESSIVE RAIN WILL BE
VALID FROM NEAR EUREKA, CA TO THE COASTAL RANGES AND THE CASCADES
OF WASHINGTON ON FRIDAY AS AN ATMOSPHERIC RIVER ADVECTS COPIOUS
MOISTURE INLAND.
ELSEWHERE ACROSS THE NATION, LAKE ENHANCED SHOWERS FROM MICHIGAN TO
UPSTATE NEW YEAR WILL BE PREVALENT AS COLDER AIR ALOFT MOVES ACROSS
THE WARMER LAKE WATERS, BUT LIKELY TOO WARM FOR ANY SNOW THIS TIME.
BY NEXT WEEKEND, WIDESPREAD SNOW DEVELOPS ACROSS THE HIGHER TERRAIN
OF THE INTERMOUNTAIN WEST AND THE CENTRAL/NORTHERN ROCKIES AS
MULTIPLE SHORTWAVES PASS THROUGH THE AMPLIFYING UPPER TROUGH. A NEW
SURFACE LOW IS LIKELY TO DEVELOP BY MONDAY ACROSS THE
CENTRAL/NORTHERN PLAINS AS A POTENT SHORTWAVE EJECTS EASTWARD FROM
THE ROCKIES, SUPPORTING AN INCREASE IN SHOWERS/STORMS AND GUSTY
WINDS FROM THE DAKOTAS TO MISSOURI.
WARM TO HOT CONDITIONS ARE EXPECTED TO CONTINUE ACROSS THE SOUTHERN
PLAINS THROUGH NEXT WEEK WITH HIGHS RUNNING ABOUT 5 TO 15 DEGREES
ABOVE AVERAGE, EQUATING TO READINGS TOPPING OUT FROM THE MIDDLE 80S
TO MIDDLE 90S. IT SHOULD ALSO BE RATHER MILD FOR THIS TIME OF YEAR
ACROSS THE DAKOTAS THROUGH SATURDAY WITH THE UPPER RIDGE IN PLACE.
MUCH COLDER WEATHER MAKES ITS ARRIVAL FOR THE WEST COAST AND INTO
THE INTERMOUNTAIN WEST BY THE WEEKEND AS THE UPPER TROUGH BUILDS IN
ALONG WITH WIDESPREAD CLOUD COVER. TEMPERATURES SHOULD BE NEAR TO
SLIGHTLY BELOW AVERAGE FOR MOST OF THE EAST COAST STATES.
HAMRICK
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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