320
FXUS02 KWBC 020654
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EDT THU NOV 2 2023
VALID 12Z SUN NOV 5 2023 - 12Z THU NOV 9 2023
..SYNOPTIC OVERVIEW
A GENERAL QUASI-ZONAL FLOW ACROSS THE CONTINENTAL U.S. IS EXPECTED
GOING INTO THE WEEKEND, WITH BROAD CYCLONIC FLOW ALOFT OVER
SOUTHERN CANADA AND A SHORTWAVE TROUGH QUICKLY TRAVERSING THE
NORTHEASTERN U.S. ON SUNDAY. THE TROUGH THAT DEVELOPS ACROSS THE
PLAINS BY MONDAY WILL SPUR SURFACE CYCLOGENESIS ACROSS THE UPPER
MIDWEST AND GREAT LAKES REGION, AND THEN THE LOW REACHES NEW
ENGLAND ON TUESDAY. UNSETTLED CONDITIONS ARE EXPECTED TO CONTINUE
ACROSS THE PACIFIC NORTHWEST WITH MULTIPLE TROUGHS PASSING
OVERHEAD ALONG WITH ADDITIONAL ROUNDS OF RAINFALL AND MOUNTAIN
SNOW FOR THE NORTHERN ROCKIES. A CANADIAN SURFACE HIGH WILL
CONTINUE TO GOVERN THE OVERALL WEATHER PATTERN ACROSS THE NORTHERN
PLAINS WITH COLD WEATHER CONTINUING.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE MODELS CONTINUE TO STRUGGLE WITH TIMING OF SHORTWAVE FEATURES
TRACKING EAST IN THE PROGRESSIVE FLOW PATTERN, EVEN AS EARLY AS
SUNDAY WITH THE ECMWF/ECENS FASTER WITH THE LEAD TROUGH ACROSS THE
OHIO VALLEY AND THE GFS/GEFS/CMC SLOWER. FOR THE SECOND AND MORE
IMPACTFUL SHORTWAVE TROUGH/SURFACE LOW, THERE IS ACTUALLY BETTER
TIMING AGREEMENT AMONG THE GFS/ECMWF AND THEIR ENSEMBLE MEANS, BUT
THE CMC BEGINS TO DIVERGE SIGNIFICANTLY FROM THIS GROUP OF
GUIDANCE AND THE LOW IS CONSIDERABLY SLOWER AND MAINTAINS THE HIGH
OVER NEW ENGLAND LONGER. THESE DIFFERENCES WITH RECENT RUNS OF
THE CMC ONLY GROW FURTHER GOING INTO THE MIDDLE OF THE WEEK, AND
GIVEN THE DIFFERENCES BETWEEN IT AND THE ENSEMBLE MEANS, IT WAS
NOT PART OF THE PREFERRED BLEND FOR THIS FORECAST CYCLE. BY THE
END OF THE FORECAST PERIOD NEXT THURSDAY, THE 18Z GFS IS QUICKER
TO BRING IN THE NEXT STORM SYSTEM FOR THE PACIFIC NORTHWEST
COMPARED TO THE ECMWF (00Z GFS MORE IN LINE), WHICH MAINTAINS THE
RIDGE AXIS NEAR THE WEST COAST LONGER. ENSEMBLE MEANS ACCOUNTED
FOR 50-70% OF THE FORECAST BLEND BY THE WEDNESDAY-THURSDAY TIME
PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE CONTINENTAL U.S. SHOULD NOT SEE ANY SIGNIFICANT
RAINFALL HAZARDS THROUGH THIS COMING WEEKEND. SIMILAR TO THE PAST
FEW DAYS, THE ONLY REGION WHERE THERE WILL BE A RISK OF EXCESSIVE
RAINFALL LEADING TO POTENTIAL FLOODING CONCERNS WILL BE IN THE
COASTAL RANGES OF THE PACIFIC NORTHWEST WITH THE ENHANCED ONSHORE
FLOW THAT WILL CONTINUE INTO THE WEEKEND. A MARGINAL RISK OF
EXCESSIVE RAINFALL HAS BEEN MAINTAINED ON DAY 4 (SUNDAY) FROM
NORTHWESTERN CALIFORNIA TO THE OREGON CASCADES AND COASTAL RANGES.
LOCALLY HEAVIER RAINFALL ON THE WEST FACING SLOPES MAY JUST BE
ENOUGH TO CAUSE SOME MINOR FLOODING CONCERNS, ESPECIALLY IN URBAN
AND BURN SCAR AREAS. LOOKING AHEAD TO DAY 5 (MONDAY) AN ABATEMENT
OF THE ONSHORE FLOW AND ASSOCIATED RAINFALL IS EXPECTED, AND
THEREFORE NO RISK AREAS ARE PLANNED. HEAVY SNOW IS LIKELY FOR THE
HIGHEST ELEVATIONS OF THE NORTHERN ROCKIES. EXPECT PRECIPITATION
FROM THE PACIFIC NORTHWEST INTO THE ROCKIES TO GENERALLY TREND
LIGHTER BY THE MIDDLE OF NEXT WEEK AS UPPER LEVEL RIDGING BRIEFLY
BUILDS BACK IN.
ACROSS THE EASTERN HALF OF THE COUNTRY, A LEADING WEAK WAVE
BRUSHING THE GREAT LAKES AND ASSOCIATED FRONT MAY PRODUCE SOME
LIGHT PRECIPITATION OVER THE NORTHERN TIER, GREAT LAKES, AND
NORTHERN NEW ENGLAND DURING THE WEEKEND. A BETTER DEFINED SYSTEM
MAY BRING A BROADER AREA OF PRECIPITATION FROM THE GREAT LAKES TO
THE NORTHEAST STATES. CONFIDENCE IS STILL LIMITED FOR THE
REGARDING THE AREAL COVERAGE AND TIMING OF THIS PRECIPITATION DUE
TO SIGNIFICANT GUIDANCE DIFFERENCES OF THE POTENTIAL PRIMARY
SURFACE SYSTEM, AS WELL AS POSSIBLE SECONDARY WAVE DEVELOPMENT
ALONG THE TRAILING FRONT. THERE HAS BEEN A NORTHWARD TREND IN THE
GUIDANCE COMPARED TO YESTERDAY FOR THIS EVENT OVERALL. LOCATIONS
NEAR THE CANADIAN BORDER MAY SEE SOME SNOW OR MIXED PRECIPITATION
DURING THE PERIOD WHILE RAIN WILL BE THE PREVAILING PRECIPITATION
TYPE ELSEWHERE.
TEMPERATURES ARE EXPECTED TO BE PLEASANTLY MILD FOR THIS TIME OF
YEAR ACROSS MUCH OF THE CENTRAL U.S. ON SUNDAY WITH HIGHS
GENERALLY RUNNING 5 TO 15 DEGREES ABOVE EARLY NOVEMBER AVERAGES.
THIS WILL LIKELY REMAIN THE CASE GOING INTO EARLY NEXT WEEK AS
WELL, MAINLY FROM THE SOUTHERN PLAINS TO THE SOUTHEAST STATES.
MOST OF THE NATION WILL LIKELY HAVE A COOLING TREND GOING INTO THE
MIDDLE TO END OF NEXT WEEK, WITH HIGHS RUNNING UP TO 10 DEGREES
BELOW AVERAGE FROM THE INTERMOUNTAIN WEST TO THE GREAT LAKES AND
NORTHEAST 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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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