440
FXUS02 KWBC 030706
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 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 INITIAL
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
THE SLOW MOVEMENT OF THE WESTERN U.S. UPPER TROUGH SHOULD PRODUCE
A CONTINUED SOUTHWESTERLY FLOW OF MOISTURE INTO SOUTHERN
CALIFORNIA THROUGH AT LEAST TUESDAY, ALTHOUGH THE LEADING EDGE OF
THE MOISTURE SHOULD PUSH INTO THE SOUTHWEST/GREAT BASIN. THE DAY
4/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 MAY BE A LIMITING FACTOR FOR FLASH
FLOODING FOR THE ARIZONA AREA THOUGH. CONTINUED A MARGINAL RISK
ACROSS PARTS OF ARIZONA INTO WEDNESDAY AS MOISTURE MAY LINGER INTO
THE EARLY PART OF THE PERIOD, BUT THE BETTER INSTABILITY AND
MOISTURE SHOULD BE PUSHING WELL EAST BY THEN. HEAVY SNOW IN THE
HIGHER TERRAIN ACROSS MUCH OF THE WEST IS EXPECTED IN THIS OVERALL
PATTERN AS WELL, WITH POSSIBLY SIGNIFICANT MULTI-DAY TOTALS OF
MULTIPLE FEET OF SNOW FOR PARTS OF THE SIERRA NEVADA.
AS LEADING ENERGY FROM THE WESTERN TROUGH 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.
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 AND DAYTIME HIGHS MAY BE AS WARM AS 25-35F ABOVE
NORMAL THROUGH AT LEAST THURSDAY WITH INCREASING POTENTIAL FOR
DAILY TEMPERATURE RECORDS. 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 TUESDAY-WEDNESDAY.
TEMPERATURES ACROSS THE EAST SHOULD TREND WARMER AS THE WEEK
PROGRESSES WITH THE UPPER RIDGE BUILDING IN AND 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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