115
FXUS02 KWBC 270704
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
204 AM EST MON NOV 27 2023
VALID 12Z THU NOV 30 2023 - 12Z MON DEC 04 2023
..OVERVIEW
A SHORTWAVE OVER THE SOUTHWEST ON THURSDAY WILL SHIFT ACROSS THE
MIDWEST AND EVENTUALLY INTO THE NORTHEAST NEXT WEEKEND, WHICH
SHOULD BRING PERIODS OF MODERATE TO HEAVY RAINFALL ACROSS PARTS OF
THE SOUTH AND INTO THE EASTERN U.S. LATE THIS WEEK. MEANWHILE, A
SHORTWAVE OR TWO WILL MOVE INTO THE WEST LATE WEEK, PROMOTING
AMPLIFIED MEAN TROUGHING THAT SHIFTS FROM THE WEST INTO THE
CENTRAL U.S. AND THE MIDWEST THIS WEEKEND/EARLY NEXT WEEK AS UPPER
RIDGING BUILDS DOWNSTREAM ALONG THE EAST COAST. THIS SHOULD KEEP
THE WESTERN U.S. WET AND GENERALLY UNSETTLED WITH ANOTHER ROUND OF
POSSIBLY HEAVY RAINFALL TO IMPACT THE GULF COAST/SOUTHEAST
SATURDAY INTO SUNDAY.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO COME INTO BETTER AGREEMENT ON THE LARGE SCALE
PATTERN ACROSS THE CONUS DURING THE MEDIUM RANGE PERIOD, WITH A
GENERAL BLEND OF THE LATEST DETERMINISTIC GUIDANCE SERVING AS A
GOOD STARTING POINT FOR THE DAYS 3-5 PERIOD. THERE CONTINUES TO BE
SOME VARIANCE AND TIMING WITH ENERGY INTO THE WEST LATE WEEK, BUT
OVERALL GOOD AGREEMENT THAT THE PATTERN SHOULD TURN MORE AMPLIFIED
AND ACTIVE. DESPITE GOOD AGREEMENT RIGHT NOW, THE GUIDANCE HAS
STRUGGLED WITH THE EVOLUTION OVER THE WEST THE PAST COUPLE OF DAYS
AND THERE IS STILL PLENTY OF RUN TO RUN VARIABILITY. BLENDING IN
THE ENSEMBLE GUIDANCE THE SECOND HALF OF THE PERIOD SEEMED TO
MITIGATE ANY LINGERING DETAIL DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
SHORTWAVE ENERGY INTO THE MID-SOUTH AND A WARM FRONT LIFTING
THROUGH THE GULF OF MEXICO WILL ALLOW FOR INCREASING MOISTURE AND
INSTABILITY ACROSS THE GULF COAST/SOUTHEAST REGION, WITH
INCREASING CONFIDENCE IN SOME WIDESPREAD MODERATE TO HEAVY
RAINFALL BEGINNING THURSDAY AND LASTING INTO NEXT WEEKEND. SOME
UNCERTAINTY STILL IN AMOUNTS AND TIMING, BUT A MARGINAL RISK WAS
MAINTAINED FOR THE DAY 4 (THURSDAY) EXCESSIVE RAINFALL OUTLOOK
ACROSS THE LOWER MISSISSIPPI VALLEY. MODELS SHOW SOME HEAVY RAIN
LINGERING INTO FRIDAY ACROSS THE CENTRAL GULF COAST, SO A MARGINAL
RISK WAS ADDED FOR THIS REGION ON THE DAY 5 ERO. AMPLIFIED
TROUGHING SHIFTING OUT OF THE WEST THIS WEEKEND WILL PROVIDE A
RENEWED SURGE OF MOISTURE AND WIDESPREAD MODERATE TO HEAVY
RAINFALL ACROSS THE SOUTHEAST. OUT WEST, PRECIPITATION WILL
INCREASE THURSDAY INTO NEXT WEEKEND AS A SHORTWAVE OR TWO MOVE
THROUGH THE REGION, WITH SOME PRECIPITATION REACHING SOUTHWARD
INTO CALIFORNIA AND THE SOUTHWEST. THE HEAVIEST PRECIPITATION
(COASTAL RAIN AND MOUNTAIN SNOW) WILL BE ACROSS THE
WASHINGTON/OREGON COAST AND CASCADES NEXT WEEKEND WITH GENERALLY
LIGHTER AMOUNTS FARTHER INLAND.
THE INTERIOR WEST SHOULD STAY COOLER THAN NORMAL UNDERNEATH
REINFORCED TROUGHING THROUGH NEXT WEEKEND. TEMPERATURES FOR THE
REST OF THE COUNTRY SHOULD BE CLOSER TO NORMAL LATE THIS WEEK, BUT
TREND WARMER WITH TIME ACROSS THE NORTHERN PLAINS INTO THE MIDWEST
AND EVENTUALLY THE EAST BY THE WEEKEND. DAYTIME HIGHS COULD BE
5-10 DEGREES ABOVE AVERAGE ACROSS THIS REGION. THE WESTERN U.S.
MAY FINALLY TREND BACK TOWARDS NORMAL, OR ABOVE NORMAL IN SOME
PLACES EARLY NEXT WEEK AS THE TROUGH MOVES EAST AND RIDGING BUILDS
BACK IN.
SANTORELLI
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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