432
FXUS02 KWBC 311928
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EST SUN DEC 31 2023
VALID 12Z WED JAN 03 2024 - 12Z SUN JAN 07 2024
..OVERVIEW
THE MEDIUM RANGE PERIOD FEATURES A RATHER PROGRESSIVE FLOW PATTERN
WITH SYSTEMS OF MODEST AMPLITUDE MOVING WEST TO EAST ACROSS THE
LOWER 48. A SERIES OF UPPER LOWS/SHORTWAVES SHIFTING FROM THE
SOUTHWEST AND ACROSS THE SOUTHERN U.S. SHOULD HAVE THE BEST
MOISTURE TAP KEEPING THE BULK OF THE PRECIPITATION DURING THE
PERIOD CONFINED TO THE WEST COAST AND THE GULF COAST/SOUTHEAST
WHERE LOCALLY HEAVY RAIN WILL BE POSSIBLE IN SOME SPOTS. IN THE
NORTHERN STREAM, SHORTWAVES SHOULD TRAVEL ACROSS THE UPPER
MIDWEST/GREAT LAKES WITH POSSIBLE EVENTUAL INTERACTIONS WITH THE
SOUTHERN STREAM SYSTEMS OVER THE EAST. IT SHOULD BE COOLER THAN
AVERAGE IN THE WEST AND SOUTHEAST WHILE WARMER THAN AVERAGE
TEMPERATURES REMAIN FOR THE NORTHERN TIER OF THE COUNTRY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE IS GOOD AGREEMENT WITH THE FORECAST PATTERN, OTHER THAN
SOUTHERN STREAM PROGRESSION ISSUES IN THE SOUTHERN TIER OF THE
COUNTRY AND THE EAST, WHERE THE 06Z GFS WAS UNCHARACTERISTICALLY
SLOW, THOUGH NOT BY A SIGNIFICANT AMOUNT. SINCE ITS SOLUTION WAS
WITHIN THE ENSEMBLE SPREAD AND OVERALL DETERMINISTIC SPREAD WASN'T
PARTICULARLY LARGE, SAW NO REASON TO DISCOUNT IT FULLY. EARLY ON
FOR THE PRESSURES, WINDS, QPF, AND 500 HPA PATTERN, A COMPROMISE
OF THE 06Z GFS, 00Z UKMET, 00Z CANADIAN, AND 00Z ECMWF WAS USED.
LATER ON, UP TO 40% OF THE 00Z ECMWF AND 00Z NAEFS MEANS WERE
INCLUDED TO HELP DEAL WITH CYCLONE DEPTH ISSUES NEAR THE EAST
COAST. THE BIGGEST CHANGE TO CONTINUITY WAS OUT EAST, WHERE A
STRONGER SURFACE LOW NOW RESIDES OFF THE COAST NEXT SUNDAY
MORNING. THE REMAINING GRIDS WERE MOSTLY 13Z NBM DERIVED.
..WEATHER/HAZARDS HIGHLIGHTS
A SYSTEM IN THE SOUTHERN PLAINS MOVES INTO THE SOUTHEAST AND IS
EXPECTED TO TAP GULF OF MEXICO MOISTURE AND SOME INSTABILITY TO
CONTINUE TO FUEL WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS PARTS
OF THE CENTRAL GULF COAST AND SOUTHEAST ON WEDNESDAY INTO EARLY
THURSDAY. A MARGINAL RISK REMAINS IN THE FORECAST FOR THE DAY
4/WEDNESDAY EXCESSIVE RAINFALL OUTLOOK BUT THE LATEST GUIDANCE
SEEMS TO BE SUGGESTING THE HEAVIEST RAINFALL AND BETTER
INSTABILITY MAY REMAIN OFFSHORE SO IT COULD EITHER BE A MORE
URBANIZED FLOOD RISK OR EVEN DISAPPEAR IN LATER CYCLES SHOULD THE
OFFSHORE TREND CONTINUE...STAY TUNED. A CYCLONE IS FORECAST TO
APPROACH THE WEST COAST BY WEDNESDAY AND MOVE INTO THE SOUTHWEST
BY THURSDAY MAY BRING PRECIPITATION TO THE WEST COAST AND SOME
AREAS FARTHER INLAND, WITH RELATIVELY HIGHER TOTALS MOST LIKELY
OVER FAVORED TERRAIN IN PORTIONS OF CALIFORNIA. THIS SHOULD BRING
HEAVY RAINFALL BACK INTO TEXAS, THE GULF COAST, AND THE EAST LATE
WEEK/NEXT WEEKEND. DUE TO THE HEAVY RAINFALL EXPECTED EARLIER IN
THE WEEK, AND RECENT HEAVY RAINFALL IN THE EAST, THIS FOLLOWING
SYSTEM WILL ALSO NEED TO BE WATCHED FOR INCREASED FLOODING
CONCERNS. MODELS SHOW INCREASED SUPPORT FOR EAST COAST
CYCLOGENESIS WITH THIS LOW NEXT WEEKEND, SO TRENDED STRONGER WITH
THE LOW MOVING THROUGH THE SOUTHEAST AND OFFSHORE THE EAST COAST,
PER THE EARLY MORNING GUIDANCE. A NORTHERN TIER SYSTEM MAY BRING
LIGHT PRECIPITATION TO PARTS OF THE GREAT LAKES/NORTHEAST
PERIODICALLY NEXT WEEK, WITH PRECIPITATION MOVING INTO THE PACIFIC
NORTHWEST LATER IN THE WEEK AS WELL. THE BEST CHANCES FOR ABOVE
NORMAL TEMPERATURE ANOMALIES SHOULD FOCUS FROM THE NORTHERN PLAINS
INTO THE NORTHEAST, WITH READING GENERALLY 5-15 DEGREES ABOVE
NORMAL. BELOW AVERAGE TEMPERATURES SHOULD BE CONFINED ACROSS THE
SOUTH AND WEST.
ROTH/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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