520
FXUS02 KWBC 030700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST SAT FEB 03 2024
VALID 12Z TUE FEB 06 2024 - 12Z SAT FEB 10 2024
...ATMOSPHERIC RIVER WINDING DOWN OVER CALIFORNIA BY TUESDAY WITH
MOISTURE ALSO SPREADING INLAND ACROSS THE WEST...
..OVERVIEW
AN ACTIVE WEATHER PATTERN WILL BE IN PLACE ACROSS THE WEST AS THE
PERIOD BEGINS TUESDAY WITH A LARGE SCALE POSITIVELY TILTED MEAN
TROUGH CONTINUING TO PROMOTE A STRONG SOUTHWESTERLY FLOW OF
MOISTURE INTO THE WEST THROUGH ABOUT MIDWEEK. SIGNIFICANT RAIN AND
MOUNTAIN SNOWS EXPECTED ACROSS CALIFORNIA EARLIER IN THE WEEK
SHOULD BE WANING BY TUESDAY, BUT THERE SHOULD BE SOME LINGERING AT
LEAST LOCALLY HEAVY RAINFALL ACROSS SOUTHERN CALIFORNIA WITH
MOISTURE ALSO EXTENDING INTO PARTS OF THE INTERMOUNTAIN WEST AND
ROCKIES. ENERGY FROM THE MEAN RIDGE OVER THE WEST WILL EJECT INTO
THE CENTRAL U.S. AS A STRONG UPPER RIDGE INITIALLY ACROSS THE
CENTRAL U.S. WILL SUPPORT WELL ABOVE NORMAL TEMPERATURES OVER MUCH
OF THIS REGION, DRIFTING SLOWLY EASTWARD THROUGH THE LATTER PART
OF THE WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE CONTINUES TO BE REASONABLY AGREEABLE ON THE OVERALL
LARGE-SCALE PATTERN DURING THE MEDIUM RANGE PERIOD, BUT THERE ARE
SOME NOTABLE KEY DIFFERENCES WITH SENSIBLE WEATHER IMPACTS. THESE
DIFFERENCES MAINLY FOCUS OUT WEST AS MULTIPLE PIECES OF ENERGY DIG
DOWN THE WESTERN SIDE AND MERGE WITH THE MAIN TROUGH. EVEN AS
EARLY AS WEDNESDAY, THE GFS AND CMC WERE NOTABLY STRONGER WITH
ENERGY INTO THE PACIFIC NORTHWEST, BOTH SHOWING A CLOSED LOW OVER
THIS REGION ON THURSDAY/FRIDAY WITH A MORE SOUTHWARD PROGRESSION.
THE GFS HAS BEEN FAIRLY CONSISTENT IN SHOWING THIS EVOLUTION, JUST
WITH VARIABILITY IN THE TIMING/SHAPE OF THE UPPER LOW. THE ECMWF
ON THE OTHER HAND HAS BEEN CONSISTENT IN A WEAKER INTIAL SHORTWAVE
MIDWEEK AND EVENTUALLY A MORE PROGRESSIVE AMPLIFIED TROUGH INTO
THE CENTRAL U.S. NEXT SATURDAY. THERE IS ALSO NOTABLE, BUT FAIRLY
TYPICAL, DIFFERENCES WITH LEADING ENERGY AS IT EJECTS OUT OF THE
MEAN TROUGH EARLY WEEK LIFTING INTO THE UPPER MIDWEST AROUND
THURSDAY-FRIDAY. THE ECMWF CONTINUES TO BE A LITTLE NORTH OUTLIER
WITH THE RESULTING SURFACE LOW.
THE WPC FORECAST FOR TONIGHT WAS ABLE TO UTILIZE A DETERMINISTIC
MODEL BLEND FOR THE FIRST COUPLE OF DAYS, DESPITE THE GROWING
UNCERTAINTY OUT WEST. THOUGH BY THURSDAY, INCREASING AMOUNTS OF
THE ENSEMBLE MEANS WERE INCORPORATED TO ATTEMPT TO SMOOTH OUT THE
DIFFERENCES. THE ENSEMBLE MEANS WERE RELATIVELY CONSISTENT WITH
EACH OTHER AND PROVIDED A GOOD STARTING POINT TO THE FORECAST,
WITH SOME LESSER AMOUNTS OF THE DETERMINISTIC GFS/ECMWF FOR ADDED
SYSTEM DEFINITION. THIS MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
A MODERATE TO STRONG ATMOSPHERIC RIVER WILL BE ONGOING AS THE
PERIOD BEGINS MONDAY WITH WELL ABOVE NORMAL MOISTURE SUPPORTING
SIGNIFICANT TO EXTREME RAINFALL ACROSS PARTS OF SOUTHERN
CALIFORNIA. GUIDANCE INDICATES MULTI-DAY TOTALS (DAY 3 INTO DAY 4)
POSSIBLY NEAR A FOOT FOR SOUTHERN FACING TERRAIN NEAR THE
TRANSVERSE RANGES. ESPECIALLY CONSIDERING THE EARLY STAGE OF THE
AR THIS WEEKEND WILL PRE-CONDITION SOILS, A MODERATE RISK REMAINS
IN EFFECT ON THE DAY 4/MONDAY EXCESSIVE RAINFALL OUTLOOK. WITH THE
SOUTHEASTWARD MOVEMENT OF THE AR, THE RISK AREAS EXPAND FARTHER
INTO SOUTHERN CALIFORNIA COMPARED TO THE SHORT RANGE/SUNDAY
OUTLOOK, BUT CERTAINLY WITH SOME OVERLAP BETWEEN DAYS 3 AND 4.
MODEL TRENDS HAVE BEEN SLIGHTLY FASTER TO BRING HEAVY RAIN INTO
THE SAN DIEGO AREA BY MONDAY AND THUS EXPANDED THE MODERATE RISK
FARTHER SOUTH THERE. THE SLOW MOVEMENT OF THE SUPPORTING UPPER
TROUGH SHOULD PRODUCE A CONTINUED SOUTHWESTERLY FLOW OF MOISTURE
INTO THE REGION THROUGH AT LEAST TUESDAY, ALTHOUGH THE LEADING
EDGE OF THE MOISTURE SHOULD PUSH INTO THE SOUTHWEST/GREAT BASIN.
THE DAY 5/TUESDAY ERO SHOWS A BROAD MARGINAL RISK AREA FROM
SOUTHERN CALIFORNIA INTO THE SOUTHWEST, WITH SMALLER SLIGHT RISKS
HIGHLIGHTED FOR THE LA-SAN DIEGO CORRIDOR AS WELL AS ACROSS PARTS
OF WEST-CENTRAL ARIZONA. LACK OF INSTABILITY UNTIL AFTER THE
TROUGH/FRONT COME THROUGH AND LIMIT MOISTURE MAY BE A LIMITING
FACTOR FOR FLASH FLOODING FOR THE ARIZONA AREA THOUGH. HEAVY SNOW
IN THE HIGHER TERRAIN ACROSS MUCH OF THE WEST IS EXPECTED IN THIS
PATTERN, WITH POSSIBLY SIGNIFICANT MULTI-DAY TOTALS OF MULTIPLE
FEET OF SNOW FOR PARTS OF THE SIERRA NEVADA.
AS LEADING ENERGY FROM THE WESTERN TROUGH LIFTS EJECTS INTO THE
PLAINS, THIS SHOULD HELP SPIN UP A MODERATELY DEEP SURFACE CYCLONE
THAT TRACKS NORTHEASTWARD WITH TIME INTO THE UPPER MIDWEST LATE
WEEK. THE ASSOCIATED COLD FRONT SHOULD HELP PULL MOISTURE
NORTHWARD TO FUEL PRECIPITATION, WITH POSSIBLE SNOW IN THE
NORTH-CENTRAL U.S., THOUGH WITH STILL PLENTY OF UNCERTAINTY IN THE
EXACT AMOUNTS AND PLACEMENT. IN THE SOUTHEAST, THE HEAVIEST
PRECIPITATION SHOULD BE MOVING OFF THE COAST BY MONDAY AS A STRONG
SURFACE LOW MOVES ACROSS FLORIDA, BUT SOME MOISTURE MAY WRAP BACK
IN ACROSS THE SOUTHEAST TO FUEL SOME LINGERING SHOWERS AND
THUNDERSTORMS.
THE UPPER RIDGE FROM THE SOUTHERN PLAINS THROUGH GREAT LAKES WILL
SUPPORT A BROAD AREA OF UNSEASONABLY WARM TEMPERATURES OVER THE
CENTRAL U.S. AND MIDWEST THROUGH THE PERIOD. CONTINUE TO EXPECT
THE GREATEST ANOMALIES TO BE OVER/NEAR THE UPPER MIDWEST WHERE
MORNING LOWS MAY BE AS WARM AS 25-35F ABOVE NORMAL AND EXCEED
DAILY RECORDS FOR MULTIPLE DAYS, WHILE DAYTIME HIGHS SHOULD BE A
LITTLE LESS EXTREME, UP TO 15-25F OR SO ABOVE NORMAL. IN CONTRAST,
THE SOUTHWEST U.S./CALIFORNIA SHOULD SEE COOL DAYTIME HIGHS
THROUGH THE PERIOD WITH A FEW LOCATIONS UP TO ABOUT 10F BELOW
NORMAL ON ONE OR MORE DAYS. CLOUDS/PRECIPITATION OVER THE WEST
SHOULD KEEP MORNING LOWS NEAR TO ABOVE NORMAL UNTIL LATER NEXT
WEEK. FLORIDA SHOULD SEE A COUPLE COOL DAYS WITH HIGHS 5-10F BELOW
NORMAL BY MONDAY-TUESDAY AFTER PASSAGE OF THE SOUTHEAST SYSTEM.
TEMPERATURES ACROSS THE EAST SHOULD TREND WARMER AS THE WEEK
PROGRESSES WITH THE UPPER RIDGE BUILDING IN. DAYTIME HIGHS BY NEXT
FRIDAY COULD BE APPROACHING 10-20 DEGREES ABOVE NORMAL FOR SOME
LOCATIONS.
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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