119
FXUS02 KWBC 150658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST THU FEB 15 2024
VALID 12Z SUN FEB 18 2024 - 12Z THU FEB 22 2024
***MULTIPLE ATMOSPHERIC RIVER EVENTS POSSIBLE FOR PORTIONS OF
CALIFORNIA WITH HEAVY RAIN AND SIERRA SNOW***
..GENERAL OVERVIEW
AN UPPER LEVEL TROUGH INITIALLY OVER THE GREAT LAKES AND NORTHEAST
U.S. THIS WEEKEND IS FORECAST TO RETREAT NORTHWARD AND ALLOW FOR
MORE OF A ZONAL FLOW PATTERN ACROSS THE EASTERN U.S. TO BEGIN NEXT
WEEK. THE SURFACE LOW FROM THE GULF WILL CROSS FLORIDA EARLY ON
SUNDAY AND THEN MOVE OFFSHORE, KEEPING MOST OF THE ADVERSE WEATHER
IMPACTS AWAY FROM THE SOUTHEAST U.S. COAST. MEANWHILE, AN UPPER
LEVEL RIDGE IS EXPECTED TO BE IN PLACE ACROSS THE ROCKIES AND
PORTIONS OF THE INTERMOUNTAIN WEST EARLY IN THE WEEK, AND THIS
WILL TEND TO SLOW THE OVERALL PROGRESSION OF PACIFIC DISTURBANCES.
OVERALL, THE WEST COAST REGION IS EXPECTED TO BE QUITE UNSETTLED
WITH MULTIPLE ROUNDS OF MODERATE TO HEAVY RAINFALL WITH
ATMOSPHERIC RIVER EVENTS, AND HEAVY SNOW FOR THE SIERRA AND
NORTHERN CALIFORNIA MOUNTAIN RANGES, AND MODERATE SNOW FOR
PORTIONS OF THE CENTRAL AND NORTHERN ROCKIES BY MID-WEEK AS THE
UPPER LEVEL RIDGE BREAKS DOWN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE IS IS GOOD OVERALL SYNOPTIC SCALE
AGREEMENT TO BEGIN THE FORECAST PERIOD ON SUNDAY, AND A GENERAL
MODEL BLEND SUFFICES AS A GOOD STARTING POINT IN THE FORECAST
PROCESS. THIS ALSO HOLDS TRUE GOING INTO MONDAY, ALTHOUGH
DIFFERENCES IN THE PLACEMENT OF THE SURFACE LOW OFF THE CALIFORNIA
COAST BEGIN BECOMING MORE APPARENT. LOOKING AHEAD TO THE MIDDLE
OF THE WEEK, THE BEST OVERALL MODEL AGREEMENT IS ACROSS THE
EASTERN U.S. WITH THE SURFACE HIGH STRETCHED FROM THE GULF COAST
TO NEW ENGLAND, BUT MORE DISPERSION WITH THE SURFACE LOW THAT IS
LIKELY TO DEVELOP ACROSS THE MIDWEST AND THEN THE OHIO VALLEY
REGION. THE ECMWF IS MORE PROGRESSIVE WITH THE PACIFIC/CALIFORNIA
TROUGH MOVING INLAND ACROSS THE INTERMOUNTAIN WEST BY THE END OF
THE FORECAST PERIOD COMPARED TO THE CMC/GFS. BY THE
WEDNESDAY-THURSDAY TIME PERIOD, THE ENSEMBLE MEANS ACCOUNTED FOR
ABOUT 50-65% OF THE FORECAST BLEND OWING TO TIMING AND PLACEMENT
DIFFERENCES WITH THE LOW OVER THE MIDWEST.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE SIGNIFICANT RAINFALL ASSOCIATED WITH THE GULF LOW ON
SUNDAY SHOULD BE CONFINED TO THE SOUTHERN HALF OF THE FLORIDA
PENINSULA, AND THEN MOVING OFFSHORE ENTIRELY BY MONDAY. HOWEVER,
THERE WILL LIKELY BE SOME HEAVIER CONVECTIVE ELEMENTS ACROSS THE
GULF STREAM AND OVER COASTAL PORTIONS OF THE SOUTH FLORIDA METRO
AREAS, AND THIS COULD RESULT IN A POTENTIAL FOR SOME FLOODING IF
THIS CONVECTION TRAINS OVER THE SAME AREAS, SO THE MARGINAL RISK
AREA WILL BE MAINTAINED FOR THE DAY 4 PERIOD FROM ST. LUCIE DOWN
TO THE GREATER MIAMI METRO AREA.
THE PROSPECTS FOR HEAVY RAINFALL AND POTENTIAL FLOODING ARE EVEN
GREATER ACROSS MUCH OF CALIFORNIA GOING INTO SUNDAY AND EVEN MORE
SO ON MONDAY. A SLIGHT RISK IS PLANNED FOR THE CENTRAL CALIFORNIA
COAST AND COASTAL MOUNTAINS FROM SAN FRANCISCO TO NEAR SANTA MARIA
ON SUNDAY WHERE THE BEST MOISTURE FLUX AND HIGHEST PW ANOMALIES
ARE EXPECTED. A SLIGHT RISK AREA IS ALSO PLANNED FOR THE COASTAL
MOUNTAIN RANGES, INCLUDING THE TRANSVERSE RANGES, FOR THE DAY 5
PERIOD MONDAY-MONDAY NIGHT, INCLUDING THE GREATER LOS ANGELES
METRO AREA, AS THE ATMOSPHERIC RIVER AND ASSOCIATED ANOMALOUS
MOISTURE FLUX IS DIRECTED AT THE TERRAIN AND PRODUCES 2 TO LOCALLY
4 INCHES OF RAINFALL DURING THIS TIME. HEAVY SNOW IS EXPECTED FOR
THE SIERRA, AND MODERATE SNOW FARTHER INLAND ACROSS THE HIGHER
TERRAIN OF THE INTERMOUNTAIN WEST AND EVENTUALLY THE ROCKIES.
AFTER THE BRIEF COLD SPELL ACROSS THE NORTH-CENTRAL U.S. ON
SATURDAY, A WARMING TREND IS EXPECTED GOING INTO SUNDAY, AND
ESPECIALLY EARLY NEXT WEEK AS THE UPPER TROUGH LIFTS OUT AND MORE
WESTERLY FLOW FROM THE PACIFIC MOVES IN AND MODIFIES THE AIR MASS.
HIGH TEMPERATURES COULD BE 15-25 DEGREES ABOVE AVERAGE ACROSS
PORTIONS OF THE CENTRAL PLAINS AND MIDWEST BY TUESDAY. CLOUDS AND
PRECIPITATION ACROSS THE WEST COAST REGION WILL TEND TO HOLD
TEMPERATURES MORE IN CHECK, WITH SLIGHTLY BELOW AVERAGE READINGS
LIKELY.
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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