615
FXUS02 KWBC 201913
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 PM 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 MODEL GUIDANCE HAS REMAINED PRETTY CONSISTENT ACROSS THE BOARD
IN SHOWING AN AMPLIFYING PATTERN LATER THIS WEEK AS AN UPPER-
LEVEL CLOSED LOW BROADENS OVER THE GREAT LAKES REGION, AN UPPER-
RIDGE AMPLIFIES OVER THE WESTERN TO CENTRAL NORTHERN TIER OF THE
U.S., AND AN UPPER-TROUGH DIGS SOUTHWARD ALONG THE WEST COAST.
ANOTHER FEATURE OF NOTE HAS BEEN A SOUTHERN STREAM UPPER-WAVE
FORECAST TO MOVE EASTWARD ACROSS THE SOUTHWESTERN TO SOUTH-CENTRAL
U.S., WHICH ALSO REMAINS WELL-CAPTURED BY ALL THE GUIDANCE. THE
CONSISTENCY AND AGREEMENT SUPPORTED A COMPOSITE BLEND OF THE 00Z
GFS/ECMWF/CMC/UKMET FOR THE FIRST PART OF THE FORECAST PERIOD.
DIFFERENCES BEGIN TO EMERGE INTO THE WEEKEND WITH THE UKMET
CONTINUING TO SHOW AN APPROACHING UPSTREAM SHORTWAVE AND ASSOCIATED
DEEP SURFACE LOW OVER THE NORTHEASTERN PACIFIC TO PACIFIC
NORTHWEST COMPARED TO THE REST OF THE GUIDANCE. THE ECMWF, GFS, AND
CMC SOLUTIONS ALSO BEGIN TO DIVERGE WITH RESPECT TO THE EVOLUTION
OF THE UPPER-TROUGH AS IT SHIFTS EASTWARD OVER THE WESTERN U.S. THE
CMC PRESENTS A MORE ZONAL PATTERN WITH THE UPPER- FLOW REMAINING
FURTHER NORTH, WHILE THE GFS IS MORE AMPLIFIED WITH THE UPPER-
TROUGH AS IT APPROACHES THE CENTRAL U.S., AND THE ECMWF INITIALLY
IN BETWEEN. THE ECMWF ALSO EVENTUALLY TRENDS THE DIRECTION OF THE
GFS, THOUGH WITH BOTH MODELS BEGINNING TO SHOW SIGNIFICANT
DIFFERENCES IN EMBEDDED SHORTWAVE ENERGIES BY LATE NEXT
WEEKEND/EARLY NEXT WEEK. THE MEANS TEND TO FOLLOW THEIR RESPECTIVE
CENTER'S DETERMINISTIC MODEL TREND. FOR THE MID- TO LATE PART OF
THE PERIOD, THE UKMET AND THEN CMC WERE ADJUSTED DOWN/REMOVED FROM
THE BLEND GIVEN INCREASING DIFFERENCES COMPARED TO THE GFS/ECMWF
AND THEIR RESPECTIVE MEANS. THE MEANS WERE INCREASED UP TO 50% OF
THE BLEND BY THE END OF THE PERIOD GIVEN THE INCREASING SIGNIFICANT
DIFFERENCES OF THE NOTED EMBEDDED SHORTWAVE ENERGY OF THE UPPER-
TROUGH APPROACHING THE CENTRAL U.S. THERE ARE ALSO INCREASING
DIFFERENCES WITH RESPECT TO REINFORCING UPPER- ENERGY AS THE UPPER-
LOW/TROUGH LIFTS NORTHEASTWARD FROM THE GREAT LAKES/NORTHEAST
VICINITY.
..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. THE DETERMINISTIC GUIDANCE
SUGGESTS PATCHY QPF MAXIMA ON THE ORDER OF 2 TO 4 INCHES ARE
POSSIBLE FROM EASTERN KANSAS TO THE ARKLATEX REGION THROUGH FRIDAY,
AND HIGHER RAINFALL RATES WITH THE STORMS THAT DEVELOP COULD LEAD
TO SOME INSTANCES OF FLASH FLOODING. A MARGINAL RISK HAS BEEN
MAINTAINED FOR BOTH THURSDAY AND FRIDAY ACROSS THIS REGION, WITH
THE POTENTIAL FOR A GREATER RISK, ESPECIALLY ON FRIDAY, WITH MORE
CONFIDENCE IN THE MESOSCALE DETAILS GIVEN THE TREND TOWARDS THESE
HIGHER AMOUNTS. DRY ANTECEDENT CONDITIONS ALSO PRECLUDE A HIGHER
RISK FOR NOW. 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. HIGH WINDS AND WAVES CAN ALSO BE EXPECTED ALONG
THE COAST OF THE PACIFIC NORTHWEST WITH THE PASSAGE OF THE SYSTEM
THURSDAY-SATURDAY.
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.
PUTNAM/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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