432
FXUS02 KWBC 200659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST TUE FEB 20 2024
VALID 12Z FRI FEB 23 2024 - 12Z TUE FEB 27 2024
..OVERVIEW
AN UPPER RIDGE TRAVERSING THE COUNTRY LATE THIS WEEK INTO EARLY
NEXT WEEK WILL SPREAD MUCH ABOVE NORMAL TEMPERATURES PARTICULARLY
TO THE PLAINS AND MIDWEST. TROUGHING WILL BE IN PLACE ACROSS THE
EAST LATE THIS WEEK AHEAD OF THE RIDGE, WITH SOME PRECIPITATION
ACROSS THE EASTERN SEABOARD FRIDAY AND COOLER TEMPERATURES BY
SATURDAY BEHIND A COLD FRONT, BEFORE TRANSITIONING TO MORE ZONAL
FLOW. MEANWHILE AN EASTERN PACIFIC UPPER LOW SHOULD SPREAD SOME
INCREASING PRECIPITATION CHANCES TO THE WEST COAST ONCE AGAIN,
POSSIBLY BY LATE WEEK BUT MORE CONFIDENTLY BY EARLY NEXT WEEK AS
NORTHERN AND SOUTHERN STREAM TROUGHING PHASE AND TRACK INTO THE
WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS RATHER AGREEABLE ON THE SYNOPTIC SCALE THROUGH
THE WEEKEND, INCLUDING EAST-CENTRAL U.S. TROUGHING ON FRIDAY
SHIFTING INTO THE EAST AND THEN THE ATLANTIC BY SUNDAY, THE UPPER
LOW IN THE EASTERN PACIFIC, AND RIDGING IN BETWEEN. A MULTI-MODEL
DETERMINISTIC BLEND OF THE 12/18Z GFS AND 12Z ECMWF, CMC, AND
UKMET WORKED WELL TO BLEND OUT SMALLER DIFFERENCES FOR A
COMPROMISE SOLUTION.
THE MOST UNCERTAIN ASPECT OF THE FORECAST IS HOW QUICKLY THE UPPER
LOW IN THE EASTERN PACIFIC TRACKS EAST INTO THE WESTERN U.S. EARLY
NEXT WEEK. MODEL GUIDANCE SHOWS NORTHERN STREAM TROUGHING DIGGING
SOUTHEASTWARD AT THE SAME TIME, AND THEIR PHASING LIKELY PLAYS A
ROLE IN THE TIMING DIFFERENCES. WITH THE 12/18Z MODEL CYCLE, THE
GFS/GEFS MEAN WERE QUICKER TO BRING THE SOUTHERN STREAM TROUGH
INTO THE SOUTHWEST BY EARLY MONDAY COMPARED TO THE SLOWER ECMWF
AND EC MEAN, WITH THE CMC IN BETWEEN. INTERESTINGLY, MOST OF THE
12Z ECMWF-BASED MACHINE LEARNING/AI MODELS WERE EVEN SLOWER THAN
THE OPERATIONAL RUN. THIS LED US TO WEIGHT THE EC/EC MEAN SOMEWHAT
MORE IN THE MODEL BLEND TO PRODUCE A SLOWER SOLUTION THAT WAS MORE
OF A COMPROMISE BETWEEN THE FASTER GFS SUITE AND THE SLOWER
MACHINE LEARNING MODELS, SO SLOWER THAN CONTINUITY. THE INCOMING
00Z OPERATIONAL GUIDANCE ALL TEND TO BE SLOWER THAN THEIR PREVIOUS
RUNS SO THIS SEEMS LIKE A GOOD CHOICE FOR NOW. THE 00Z ECMWF MAY
BE TOO FAR WEST THOUGH. BY TUESDAY THERE IS A LITTLE BIT BETTER
AGREEMENT WITH THE PHASED TROUGH AXIS. HOWEVER THE 12Z AND NOW 00Z
CMC HAVE BEEN BRINGING UPSTREAM TROUGHING/ENERGY TOWARD BRITISH
COLUMBIA WHERE GFS/ECMWF RUNS SHOW RIDGING, AND THIS AFFECTS THE
DOWNSTREAM FLOW SOMEWHAT. SO BY THE LATE FORECAST PERIOD, PHASED
OUT THE CMC WHILE MAINTAINING THE ECMWF AND A BIT OF THE GFS IN
THE BLEND WHILE INCREASING THE PROPORTION OF ENSEMBLE MEANS TO
OVER HALF BY DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
LIGHT TO MODERATE PRECIPITATION IS FORECAST FOR THE EASTERN
SEABOARD ON FRIDAY AHEAD OF A COLD FRONT. HIGHER ELEVATIONS OF NEW
YORK AND NEW ENGLAND HAVE RELATIVELY HIGHER PROBABILITIES OF
SEEING NOTABLE SNOW WITH THIS ACTIVITY BUT THE DETAILS OF THE
EXACT LOW TRACK AND TEMPERATURES WILL DETERMINE PLACEMENT AND
AMOUNTS OF SNOW. BRISK WINDS ARE ALSO POSSIBLE FOR NEW ENGLAND
PARTICULARLY LATE FRIDAY INTO SATURDAY AS THE SURFACE LOW
STRENGTHENS. BEHIND THIS SYSTEM, PARTS OF THE GREAT LAKES MAY SEE
MOSTLY LIGHT SNOW FROM A COMBINATION OF LAKE EFFECT AND LAKE
ENHANCED ACTIVITY CAUSED BY NEARBY FRONTS THIS WEEKEND INTO EARLY
NEXT WEEK.
AN UPPER LOW AND ITS SURFACE REFLECTION LOOK TO MEANDER IN THE
EASTERN PACIFIC LATE THIS WEEK, PERHAPS REACHING CLOSE ENOUGH TO
CALIFORNIA TO PROVIDE SOME SHOWER ACTIVITY. BUT BY SUNDAY MODEL
GUIDANCE IS MORE AGREEABLE THAT PRECIPITATION SHOULD SPREAD INTO
THE PACIFIC NORTHWEST AND CALIFORNIA WITH SOME MOISTURE SPREADING
FARTHER INLAND INTO THE INTERMOUNTAIN WEST. SNOW AND RAIN SHOULD
CONTINUE TO INCREASE IN INTERIOR PARTS OF THE WEST INTO MONDAY,
WHILE ANOTHER LOW PRESSURE/FRONTAL SYSTEM PROVIDES FORCING TO
INCREASE PRECIPITATION (MAINLY IN THE FORM OF RAIN GIVEN THE
ANOMALOUS WARMTH) IN THE MIDWEST.
WARMER THAN AVERAGE TEMPERATURES BY 10-20 DEGREES IN THE CENTRAL
U.S. ON FRIDAY LOOK TO ONLY INCREASE IN COVERAGE AND MAGNITUDE BY
THE WEEKEND AND EARLY NEXT WEEK. TEMPERATURES OF 20-30F ABOVE
AVERAGE WILL STRETCH FROM THE NORTHERN PLAINS/UPPER MIDWEST
SATURDAY SOUTHWARD INTO THE PLAINS AND MISSISSIPPI VALLEY EARLY
NEXT WEEK. THIS PUTS ACTUAL TEMPERATURES INTO THE 80S AND EVEN 90S
IN TEXAS MONDAY-TUESDAY WHILE 50S AND POSSIBLY EVEN 60S REACH THE
DAKOTAS. A GRADUAL EASTWARD SPREAD/SHIFT SHOULD WARM THE SOUTHEAST
IN TO THE 70S NEXT WEEK. THE EAST LOOKS TO BE ABOVE AVERAGE FRIDAY
BUT NEAR TO BELOW AVERAGE SATURDAY BEHIND A COLD FRONT, GRADUALLY
WARMING NEXT WEEK. MEANWHILE THE WEST IS FORECAST TO SEE NEAR TO
SLIGHTLY ABOVE NORMAL TEMPERATURES LATE WEEK INTO THE WEEKEND, BUT
COOLING TO BELOW NORMAL PARTICULARLY IN TERMS OF HIGHS BY
MONDAY-TUESDAY AS UPPER TROUGHING COMES IN.
TATE
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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