335
FXUS02 KWBC 301846
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 PM EST SAT DEC 30 2023
VALID 12Z TUE JAN 02 2024 - 12Z SAT JAN 06 2024
..OVERVIEW
THE LATEST GUIDANCE SHOWS A PROGRESSIVE FLOW PATTERN WITH SYSTEMS
OF MODEST AMPLITUDE MOVING WEST TO EAST ACROSS THE LOWER 48.
SYSTEMS WITH THE BEST MOISTURE TAP ARE FORECAST TO TRAVEL THROUGH
THE SUBTROPICS/SOUTHERN TIER OF THE COUNTRY. THIS TYPE OF PATTERN
KEEPS THE LOWER 48 GENERALLY MILDER THAN AVERAGE EXCEPT FOR SOME
TENDENCY TOWARDS COOLER THAN AVERAGE CONDITIONS IN THE SOUTHERN
TIER OF THE COUNTRY (ESPECIALLY THE SOUTHEAST) AND CAUSES THE BULK
OF THE PRECIPITATION CONFINED TO THE WEST COAST AND THE GULF
COAST/SOUTHEAST WITH LOCALLY HEAVY RAIN POSSIBLE IN SOME SPOTS.
OVERALL, THIS PATTERN IS TYPICAL OF WHAT ONE WOULD EXPECT WITH THE
ONGOING WARM ENSO/EL NINO CLIMATE ANOMALY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE SHOWS GOOD AGREEMENT AND THE EXPECTED FLOW PATTERN,
WITH ISSUES GENERALLY CONSTRAINED TO LATE NEXT WEEK/NEXT WEEKEND
NEAR THE GREAT LAKES/NORTHEAST (WHERE THE 06Z GFS IS STRONGER WITH
A SYSTEM THAN THE REMAINDER OF THE GUIDANCE) AND THE PACIFIC
NORTHWEST (WHERE THE 00Z ECMWF IS STRONGER WITH A SYSTEM MOVING
NEARBY). AN OVERALL BLEND OF THE DETERMINISTIC GUIDANCE SEEMED TO
PROVIDE A GOOD STARTING POINT EARLY ON, BEFORE USING UP TO 40% OF
THE 00Z NAEFS/ECMWF ENSEMBLE MEANS LATE TO DEAL WITH THE MAIN TWO
DETAIL ISSUES WITHIN THE 500 HPA, PRESSURE, WIND, AND QPF
PATTERNS. THE REMAINDER OF THE GRIDS WERE HEAVILY WEIGHTED
TOWARDS THE 13Z NBM STARTING POINT.
..WEATHER/HAZARDS HIGHLIGHTS
AN INITIAL UPPER LOW/SHORTWAVE MOVING OUT OF THE SOUTHWEST SHOULD
BEGIN TO TAP GULF OF MEXICO MOISTURE AND SOME INSTABILITY TO FUEL
WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN
PLAINS/LOWER MISSISSIPPI VALLEY ON TUESDAY. THERE IS SOME OVERLAP
BETWEEN THE HEAVIER RAINFALL/QPF SIGNAL AND THE MORE SENSITIVE
AREAS DUE TO A RECENT WET PATTERN NEAR THE MIDDLE/UPPER TEXAS
COAST, SO A MARGINAL RISK WAS MAINTAINED ON THE DAY 4/TUESDAY INTO
EARLY WEDNESDAY EXCESSIVE RAINFALL OUTLOOK COVERING MUCH OF
SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA. THIS ACTIVITY SHOULD
SHIFT EAST ALONG THE CENTRAL GULF COAST INTO THE SOUTHEAST ON
WEDNESDAY, WITH ANOTHER MARGINAL RISK FOR DAY 5/WEDNESDAY INTO
EARLY THURSDAY, THIS TIME CONFINED MAINLY ALONG THE NORTH-CENTRAL
AND NORTHEAST GULF COAST.
THE SECOND LOW FORECAST TO APPROACH THE WEST COAST BY WEDNESDAY
AND MOVE INTO THE SOUTHWEST BY THURSDAY MAY BRING ORGANIZED
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 ALSO EVENTUALLY BRING HEAVY
RAINFALL BACK INTO TEXAS AND THE GULF COAST LATE WEEK/NEXT
WEEKEND. DUE TO THE HEAVY RAINFALL EXPECTED ON TUESDAY INTO EARLY
WEDNESDAY ACROSS SOUTHEAST TX AND SOUTHWEST LA, THIS FOLLOWING
SYSTEM WILL ALSO NEED TO BE WATCHED FOR INCREASED FLOODING
CONCERNS. ELSEWHERE, NORTHERN TIER SYSTEMS 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 GREATEST TEMPERATURE ANOMALIES DURING THE PERIOD SHOULD FOCUS
ACROSS THE FAR NORTHERN TIER NEAR THE CANADIAN BORDER AND INTO THE
GREAT LAKES/NORTHEAST WITH SOME LOCATIONS SEEING MULTIPLE DAYS
WITH READINGS 10-20F OR SO ABOVE NORMAL, WITH MORNING LOWS TENDING
TO BE FARTHER ABOVE NORMAL THAN DAYTIME HIGHS. MOST AREAS FROM
CALIFORNIA EASTWARD ACROSS THE SOUTHERN TIER, PARTICULARLY THE
SOUTHEAST, SHOULD SEE NEAR TO BELOW NORMAL HIGH TEMPERATURES
DURING THE PERIOD AS A SERIES OF UPPER LEVEL SYSTEMS MOVE THROUGH.
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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