781
FXUS02 KWBC 220658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST THU FEB 22 2024
VALID 12Z SUN FEB 25 2024 - 12Z THU FEB 29 2024
..OVERVIEW
AN UPPER RIDGE TRAVERSING THE CENTRAL AND EASTERN U.S. FOR THE
FIRST HALF OF NEXT WEEK WILL SPREAD MUCH ABOVE NORMAL TEMPERATURES
TO THE PLAINS AND MIDWEST AND EVENTUALLY THE EAST. MEANWHILE
NORTHERN AND SOUTHERN STREAM TROUGHING LOOK TO TRACK INTO THE WEST
AND BRING COOLER TEMPERATURES, LOWER ELEVATION RAIN AND HIGHER
ELEVATION SNOW, AND WINDY CONDITIONS FOR THE WEST COAST TO THE
ROCKIES THROUGH EARLY-MID NEXT WEEK. INCREASED PRECIPITATION IS
ALSO LIKELY FOR THE OHIO VALLEY/GREAT LAKES BY MONDAY AND BEYOND
WITH A FRONTAL SYSTEM OR TWO AHEAD OF THIS TROUGH.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR MULTIPLE FORECAST CYCLES, OPERATIONAL MODEL GUIDANCE HAS BEEN
AGREEABLE THAT A SOUTHERN STREAM UPPER LOW IN THE EASTERN PACIFIC
OFFSHORE OF CALIFORNIA EMBEDDED IN A POSITIVELY TILTED UPPER
TROUGH WILL PHASE WITH STRONG NORTHERN STREAM ENERGY/TROUGHING AS
IT ALL TRACKS INTO THE WESTERN TO CENTRAL U.S. FOR THE FIRST HALF
OF NEXT WEEK.ÂUPPER RIDGING IS FORECAST DOWNSTREAM OF THIS IN THE
SOUTHERN STREAM, TRACKING FROM THE SOUTHWEST INTO THE CENTRAL TO
EASTERN U.S. AT THE SAME TIME. DETERMINISTIC MODELS DIVERGE
SOMEWHAT MORE NOTABLY WITH THE TIMING OF THE TROUGH BY
WEDNESDAY-THURSDAY AS IT TRACKS EAST. THE 18Z AND NOW 00Z GFS RUNS
ARE ON THE SLOW SIDE IN ITS TRACK AND EVEN SHOW AN UPPER LOW
CLOSING OFF. THE ECMWF WAS MORE OF A MIDDLE GROUND AND ALIGNED
WITH ENSEMBLE MEANS, WHICH WAS FAVORED, WHILE THE CMC RUNS ARE A
BIT FASTER THAN CONSENSUS.
HOWEVER, DESPITE THE RELATIVELY GOOD AGREEMENT IN MOST OPERATIONAL
MODELS, CONFIDENCE FOR THE NORTHERN AND SOUTHERN STREAM TROUGHS TO
PHASE AS THEY SHIFT EASTWARD IS NOT NECESSARILY HIGH. CLUSTER
ANALYSIS AND SPAGHETTIS OF HEIGHT LINES SHOW SOME ENSEMBLE MEMBERS
HAVE THE NORTHERN STREAM TROUGHING OUTPACING THE SOUTHERN STREAM
LOW, RUSHING THE NORTHERN TROUGH FORWARD AND HOLDING BACK THE
SOUTHERN LOW/TROUGH. ALSO NOTABLE IS THAT MOST (FOUR) 12Z
ECMWF-BASED AI MODELS HAVE NOTABLE STREAM SEPARATION, WITH ONLY
ONE AVAILABLE CLOSER TO THE OPERATIONAL ECMWF. THE 12Z GFS RUN OF
THE AI GRAPHCAST ALSO SWITCHED TO SHOWING SOME STREAM SEPARATION
AFTER MORE PHASED PREVIOUS RUNS. A PATTERN LIKE THIS CAN BE QUITE
TENUOUS AND THE ENERGY THAT ENDS UP FORMING THE NORTHERN STREAM
TROUGHING IS STILL OVER SIBERIA AT THIS POINT, SO IT IS POSSIBLE
THAT MORE STREAM SEPARATION WILL BE WHAT VERIFIES. FOR NOW, KEPT
WITH AN OPERATIONAL MODEL BLEND FAVORING THE 12Z MODELS AND
GRADUALLY INCREASED THE MEANS TO HALF THE BLEND BY DAY 7, WHICH
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS FORECAST FOR DAYS 3-6
AS WELL. BUT CONTINUE TO MONITOR FORECASTS AS THERE IS A CHANCE
THEY CHANGE QUITE A BIT.
..WEATHER/HAZARDS HIGHLIGHTS
AS TROUGHING COMES INTO THE WEST EARLY NEXT WEEK, PRECIPITATION
WILL SPREAD INTO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES ON
SUNDAY, INCLUDING SNOW THAT COULD BE HEAVY. PRECIPITATION MAY
BEGIN IN CALIFORNIA SUNDAY AS WELL BUT LOOKS TO INCREASE THERE BY
MONDAY. THERE IS STILL SOME MODEL SPREAD IN RAIN AMOUNTS ACROSS
COASTAL CALIFORNIA, BUT GIVEN THE SENSITIVITY OF SOUTHERN
CALIFORNIA TO ADDITIONAL RAINFALL AFTER A WET MONTH, WENT AHEAD
AND INTRODUCED A MARGINAL RISK IN THE DAY 5/MONDAY EXCESSIVE
RAINFALL OUTLOOK. IF WETTER MODELS VERIFY THIS RISK MAY NEED TO BE
UPGRADED IN FUTURE CYCLES. SNOW AND SOME RAIN SHOULD CONTINUE TO
INCREASE IN INTERIOR PARTS OF THE WEST INTO MONDAY-TUESDAY. THE
HIGHEST LIKELIHOOD FOR WINTER-RELATED IMPACTS IS IN THE CASCADES
SUNDAY-TUESDAY, BUT THE SNOW WILL LIKELY CAUSE AT LEAST MINOR
IMPACTS TO MUCH OF THE HIGHER ELEVATION AREAS OF THE SIERRA NEVADA
INTO THE INTERMOUNTAIN WEST AND ROCKIES. GUSTY WINDS ARE FORECAST
FOR THE INTERIOR WEST BEHIND A COUPLE OF COLD FRONTS ON
MONDAY-TUESDAY AS WELL.
FARTHER EAST, A COLD FRONT TRACKING THROUGH THE NORTHEASTERN U.S.
COULD SPREAD SOME LIGHT TO MODERATE PRECIPITATION FROM THE OHIO
VALLEY/GREAT LAKES INTO THE NORTHERN/CENTRAL APPALACHIANS AND THE
NORTHEAST ON SUNDAY. THEN AHEAD OF THE APPROACHING UPPER TROUGH
AND COLD FRONT, PRECIPITATION CHANCES WILL INCREASE LATE MONDAY
INTO TUESDAY IN THE MIDWEST TO THE OHIO VALLEY AND GREAT LAKES.
MOST PRECIPITATION WILL BE IN THE FORM OF RAIN GIVEN THE ANOMALOUS
WARMTH, BUT SOME SNOW ON THE BACKSIDE OF THE LOW AND COLD FRONT IN
THE NORTH-CENTRAL U.S. IS POSSIBLE, THOUGH WITH LOW CONFIDENCE.
RAINFALL AMOUNTS COULD BE LOCALLY HEAVY IN THE OHIO VALLEY, WITH
LIKELY MULTIPLE ROUNDS OF RAIN CONTINUING THROUGH AT LEAST MIDWEEK.
THE CENTRAL U.S. WILL SEE QUITE MILD TO WARM TEMPERATURES EARLY
NEXT WEEK UNDERNEATH AN UPPER RIDGE. TEMPERATURES OF 20-35 DEGREES
ABOVE AVERAGE WILL EXPAND THROUGHOUT THE PLAINS AND MISSISSIPPI
VALLEY, PUTTING ACTUAL TEMPERATURES INTO THE 80S AND EVEN 90S IN
TEXAS BY MONDAY-TUESDAY WHILE 60S REACH AS FAR NORTH AS SOUTH
DAKOTA AND IOWA, WITH POTENTIAL FOR WIDESPREAD RECORDS. THE UPPER
TROUGH AND COLD FRONT PRESSING EASTWARD SHOULD COOL TEMPERATURES
DOWN CLOSER TO NORMAL OR A FEW DEGREES BELOW IN THE CENTRAL U.S.
BY MIDWEEK, BUT TEMPERATURES COULD ALREADY START TO REBOUND BY
THURSDAY. THE WELL ABOVE NORMAL TO POSSIBLY RECORD-BREAKING
TEMPERATURES WILL GET SHUNTED EASTWARD AHEAD OF THE UPPER
TROUGH/UNDERNEATH THE UPPER RIDGE INTO THE EAST-CENTRAL AND THEN
EASTERN U.S. TUESDAY-THURSDAY. 70S SHOULD BE WIDESPREAD ACROSS THE
SOUTHEAST AND COULD EVEN REACH AS FAR NORTH AS THE MID-ATLANTIC.
MEANWHILE THE WEST IS FORECAST TO SEE NEAR TO SLIGHTLY ABOVE
NORMAL TEMPERATURES INTO SUNDAY, 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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