052
FXUS02 KWBC 150747
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
347 AM EDT WED OCT 15 2025
VALID 12Z SAT OCT 18 2025 - 12Z WED OCT 22 2025
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN RELATIVELY GOOD AGREEMENT DURING THE
MEDIUM RANGE PERIOD, HANDLING THE EVOLUTION OF SEVERAL LARGE SCALE
TROUGH/RIDGE FEATURES ACROSS THE CONUS REASONABLY WELL DESPITE A
HIGHLY AMPLIFIED 500MB FLOW PATTERN. ONLY MINOR DIFFERENCES WERE
NOTED FOR DAYS 3 AND 4, SO A COMPOSITE BLEND OF THE 00Z EC, 00Z
UKMET, 00Z CMC AND 06Z GFS DETERMINISTIC RUNS SUFFICED TO BEGIN THE
PERIOD. HOWEVER, LARGER DISCREPANCIES STARTED CROPPING UP BY DAY
5, MOST NOTABLY WITH THE EVOLUTION OF A POTENT PACIFIC TROUGH THAT
IS PROGGED TO PUSH INLAND OVER BRITISH COLUMBIA AND THE PACIFIC
NORTHWEST LATE IN THE WEEKEND INTO EARLY NEXT WEEK. WHILE THE
EC/GFS/UKMET ALL HAD SIMILAR SOLUTIONS DEPICTING THE TROUGH DIGGING
DEEPER ALONG THE WEST COAST, THE CMC SHOWS THE TROUGH BECOMING
COMPLETELY SHEARED APART AS IT MOVES ACROSS THE PACIFIC NORTHWEST.
AS A RESULT OF BEING MUCH FASTER AND FLATTER THAN CONSENSUS, THE
00Z CMC WAS REMOVED FROM THE BLEND STARTING ON DAY 5 AND WAS NOT
CONSIDERED FOR THE REMAINDER OF THE FORECAST. TO COMPENSATE, MORE
WEIGHTING WAS PLACED ON THE EPS AND GEFS ENSEMBLE MEANS, WHICH
ULTIMATELY MADE UP SLIGHTLY MORE THAN 50% OF THE BLEND FOR DAY 6
AND 7. THE GREATER WEIGHTING OF THE ENSEMBLE MEANS RESULTED IN A
MORE STABLE FORECAST THAT PRESERVED CONTINUITY WHILE REDUCING SOME
OF THE TIMING AND POSITIONAL DIFFERENCES THAT ARE TYPICAL FOR THE
LATTER HALF OF THE MEDIUM RANGE FORECAST PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
AS AN UPPER TROUGH SUPPORTED AND WAVY COLD FRONT PASSES THROUGH
THE PLAINS, MOISTURE/INSTABILITY RETURN WILL INCREASE IN ADVANCE
OF IT THROUGH THE MID-MS VALLEY WHERE RAINFALL SHOULD SIGNIFICANTLY
INCREASE BY SATURDAY. THE WPC DAY 4/SATURDAY EXCESSIVE RAINFALL
OUTLOOK (ERO) INTRODUCED A NEW SLIGHT RISK AREA CENTERED OVER THE
MID-SOUTH GIVEN FAVORABLE UPPER SUPPORT, MOISTURE AND INSTABILITY.
SPC ALSO SHOWS A THREAT FOR SEVERE WEATHER IN THIS PATTERN. THE
SLOWLY PROGRESSIVE NATURE OF THE UPPER-LEVEL AND SURFACE FEATURES
WILL SPREAD ORGANIZED RAINFALL EASTWARD INTO THE EAST/NORTHEAST
LATER WEEKEND INTO EARLY NEXT WEEK, PARTICULARLY NEAR AND ALONG THE
TRACK OF A DEEPENING/CONSOLIDATING COASTAL LOW PRESSURE SYSTEM
(AND MORE MODESTLY INTO THE SOUTHEAST AHEAD OF THE COLD FRONT). A
DAY 5/SUNDAY ERO MARINGAL RISK AREA WAS INTRODUCED TO CAPTURE LOCAL
RUNOFF POTENITAL INTO THE APPALACHIANS. TEMPERATURES WILL BE MILD
AHEAD OF THE COLD FRONT WITH HIGHS WELL INTO THE 70S/80S FRIDAY
FROM THE CORN BELT TO THE OZARKS WITH 90S ACROSS SOUTH TEXAS.
OUT WEST, ANOTHER DEEPENED SYSTEM WILL APPROACH/ENTER THE PACIFIC
NORTHWEST/WEST COAST OVER THE WEEKEND TO PRODUCE A PERIOD OF
MODERATELY HEAVY COASTAL AND VALLEY RAINS ALONG WITH HIGHER
MOUNTAIN SNOW. ACTIVITY WILL THEN DIG AND SPREAD ACROSS THE WEST
AND DOWNSTREAM TO THE ROCKIES. THE WPC DAY4/SATURDAY ERO MAINTAINS
A COASTAL WASHINGTON MARGINAL RISK AREA GIVEN A FAVORABLE SIGNAL
AND OUR WINTER WEATHER OUTLOOK SHOWS MOUNTAIN SNOW POTENIAL INLAND
FROM THE NORTHWEST TO THE NORTHERN ROCKIES INTO MONDAY WITH PASSAGE.
SCHICHTEL
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page