220
FXUS02 KWBC 291853
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 PM EST FRI DEC 29 2023
VALID 12Z MON JAN 01 2024 - 12Z FRI JAN 05 2024
..OVERVIEW
THE LATEST GUIDANCE SHOWS A PROGRESSIVE FLOW PATTERN WITH SYSTEMS
OF ONLY 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 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 IS
TYPICAL OF WHAT ONE WOULD EXPECT WITH THE ONGOING WARM ENSO/EL
NINO CLIMATE ANOMALY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL, THE GUIDANCE SHOWS EXCELLENT AGREEMENT, WITH EVEN DETAIL
ISSUES FAIRLY SMALL AND MANAGEABLE. THIS LED TO A 500 HPA,
PRESSURE, WIND, AND QPF BLEND MORE RELIANT THAN USUAL ON THE
DETERMINISTIC 06Z GFS, 00Z CANADIAN, 00Z UKMET, AND 00Z ECMWF
GUIDANCE, WITH 00Z NAEFS/00Z ECMWF ENSEMBLE MEAN CONTRIBUTIONS
ONLY TOTALING 40% BY LATE NEXT WEEK/THE END OF THE FORECAST
PERIOD. WHILE POPS WERE ADJUSTED FOR THE RESULTANT QPF, THE
REMAINDER OF THE GRIDS WERE STRONGLY BASED ON THE 13Z NBM.
..WEATHER/HAZARDS HIGHLIGHTS
AN UPPER LOW/SHORTWAVE INTO THE SOUTHWEST MAY BRING SOME LIGHT
PRECIPITATION TO PARTS OF THE REGION ON MONDAY, BUT SHOULD BEGIN
TO TAP GULF OF MEXICO MOISTURE AND SOME INSTABILITY TO FUEL MORE
WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN
PLAINS/GULF COAST/SOUTHEAST TUESDAY-WEDNESDAY. THERE IS INCREASED
OVERLAP BETWEEN THE HEAVIER RAINFALL/QPF SIGNAL AND THE MORE
SENSITIVE AREAS DUE TO A WET WEEK NEAR THE MIDDLE AND UPPER TX
COAST AND SOME RELATED LOWERED FLASH FLOOD GUIDANCE VALUES, SO A
MARGINAL RISK WAS INTRODUCED FOR PORTIONS OF SOUTHEAST TX AND
SOUTHWEST LA. 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 AND THEN EVENTUALLY BRINGING
HEAVY RAINFALL BACK INTO SOUTHEAST TX, SIMILAR TO THE PREVIOUS
SYSTEM. DUE TO THE HEAVY RAINFALL EXPECTED ON TUESDAY INTO EARLY
WEDNESDAY ACROSS SOUTHEAST TX AND SOUTHWEST LA, THIS FOLLOWING
SYSTEM BEARS WATCH.
THE GREATEST TEMPERATURE ANOMALIES DURING THE PERIOD SHOULD FOCUS
ACROSS THE FAR NORTHERN TIER NEAR THE CANADIAN BORDER 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
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page