325
FXUS02 KWBC 300657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT MON OCT 30 2023
VALID 12Z THU NOV 2 2023 - 12Z MON NOV 6 2023
..SYNOPTIC OVERVIEW
AN EXPANSIVE SURFACE HIGH WILL ENCOMPASS MUCH OF THE EASTERN U.S.
FOR THE MIDDLE TO END OF THE WEEK WITH THE HIGH SLOWLY MOVING
OFFSHORE BY THE WEEKEND. THIS AIRMASS WILL SLOWLY MODERATE AFTER
THE WIDESPREAD FROST AND FREEZE CONDITIONS EARLIER IN THE WEEK.
HOWEVER, THERE WILL LIKELY BE A RENEWED SURGE OF COLDER WEATHER
FOR THE NORTHERN PLAINS AND UPPER MIDWEST BY FRIDAY INTO NEXT
WEEKEND. A STORM SYSTEM MOVING INLAND ACROSS THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES IS EXPECTED TO INCREASE
PRECIPITATION ACROSS THESE AREAS BY THURSDAY AND CONTINUING INTO
THE END OF THE WEEK, WITH SOME SIGNAL OF AN ATMOSPHERIC RIVER
EVENT.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AGREEMENT IS GENERALLY GOOD ACROSS THE CENTRAL/EASTERN U.S.
EARLY IN THE PERIOD, BUT DIFFERENCES BECOME APPARENT AS EARLY AS
THURSDAY NEAR THE PACIFIC NORTHWEST AS THE SHORTWAVES MOVE INLAND.
THE 12Z CMC DID NOT FIT THE CONSENSUS WELL IN REGARDS TO
AMPLITUDE AND TIMING OF PACIFIC SHORTWAVE ENERGY MOVING INLAND, SO
THE FRONTS/PRESSURES FORECAST WAS BASED ON A GFS/ECMWF/UKMET BLEND
WITH SOME PREVIOUS WPC CONTINUITY, AND THEN INCREASED USE OF THE
ENSEMBLE MEANS TO ABOUT 50-60% GOING INTO SUNDAY/MONDAY. THE 00Z
CMC IS IN BETTER ALIGNMENT WITH THE CONSENSUS COMPARED TO ITS 12Z
RUN. BY THE END OF THE PERIOD NEXT MONDAY, THE FLOW IS MAINLY
ZONAL ACROSS THE NATION WITH MORE SIGNIFICANT DIFFERENCES WITH
SHORTWAVE TIMING, THUS THE INCREASE IN ENSEMBLE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE CONTINENTAL U.S. SHOULD BE RELATIVELY UNEVENTFUL IN
TERMS OF IMPACTFUL RAINFALL FOR THE END OF THE WEEK. THE
EXCEPTION TO THIS WILL BE ACROSS WESTERN OREGON AND WASHINGTON
WHERE A POTENTIAL ATMOSPHERIC RIVER EVENT MAY PRODUCE A FEW INCHES
OF RAINFALL FROM THE COASTAL RANGES OF NORTHERN CALIFORNIA TO THE
OLYMPIC MOUNTAINS FOR THE WEDNESDAY NIGHT THROUGH THURSDAY EVENING
TIME PERIOD. LOCALLY HEAVIER RAINFALL ON THE WEST FACING SLOPES
MAY JUST BE ENOUGH TO CAUSE SOME MINOR FLOOD CONCERNS, AND
THEREFORE A MARGINAL RISK OF EXCESSIVE RAINFALL REMAINS VALID FOR
THE DAY 4 PERIOD ON THURSDAY. THERE SHOULD BE ENOUGH OF A LULL ON
DAY 5 TO AVOID HAVING A MARGINAL RISK AT THIS TIME, BUT ANOTHER
ROUND OF PACIFIC MOISTURE IS EXPECTED TO ARRIVE OVER THE WEEKEND.
A SLOW MODERATION TREND WITH TEMPERATURES WILL COMMENCE FOR THE
CENTRAL AND EASTERN U.S. BY THURSDAY WITH HIGHS GENERALLY 5-15
DEGREES BELOW EARLY NOVEMBER AVERAGES, COMPARED TO THE WIDESPREAD
15-25 NEGATIVE ANOMALIES EXPECTED DURING THE SHORT RANGE FORECAST
PERIOD. TEMPERATURES CONTINUE TO WARM GOING INTO FRIDAY AND THE
WEEKEND WITH READINGS GENERALLY NEAR TO ABOUT 5 DEGREES ABOVE
AVERAGE IN MOST CASES. PLEASANTLY MILD CONDITIONS SHOULD ALSO
RETURN TO THE ROCKIES AND ADJACENT PORTIONS OF THE
CENTRAL/SOUTHERN PLAINS GOING INTO NEXT WEEKEND. HOWEVER, IT
SHOULD CONTINUE TO REMAIN QUITE CHILLY FOR NORTH DAKOTA AND INTO
NORTHERN MONTANA AND MINNESOTA WITH HIGHS GENERALLY IN THE UPPER
20S TO UPPER 30S.
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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