108
FXUS02 KWBC 221859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 PM 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
MAIN FORECAST CHALLENGE THROUGH THE MEDIUM RANGE PERIOD (SUN FEB
25 - THU FEB 29) REMAINS WITH HOW A STRONG NORTHERN STREAM TROUGH
DROPPING SOUTH FROM THE NORTHEASTERN PACIFIC AND CLOSED UPPER-LOW
IN THE SOUTHERN STREAM OFF THE COAST OF CALIFORNIA PROGRESS AND
EVOLVE TOGETHER ACROSS THE CONUS THROUGH NEXT WEEK. AHEAD OF THESE
SYSTEMS, DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT THAT A
NORTHERN STREAM SYSTEM WILL CROSS SOUTHERN CANADA/NORTHERN TIER OF
THE U.S. TOWARDS THE NORTHEAST EARLY NEXT WEEK AS WEAK RIDGING IN
THE SOUTHERN STREAM PROCEEDS THE UPPER-LEVEL ENERGY TO THE WEST,
TRANSITIONING FORM NORTHWESTERN MEXICO/THE SOUTHWEST EASTWARD
ACROSS THE SOUTHERN PLAINS TOWARDS THE SOUTHEAST. INITIAL
SHORTWAVE ENERGY FOLLOWING THE RIDGE SHOULD BRING SUBSEQUENT
CYCLOGENESIS/SURFACE SYSTEM DEVELOPMENT OVER THE PLAINS, LIFTING
NORTHEASTWARD TOWARDS THE MIDWEST. SMALLER-SCALE DETAILS WILL
LIKELY CHANGE OVER TIME BUT THE GENERAL PATTERN SHIFT TOWARDS MEAN
TROUGING IN THE WEST AS THE UPSTREAM ENERGIES APPROACH IS
AGREEABLE ACROSS THE GUIDANCE.
INITIAL EVOLUTION OF UPSTREAM NORTHERN/SOUTHERN STREAM ENERGIES IS
GENERALLY AGREEABLE AS THE NORTHERN STREAM TROUGH DROPS ACROSS THE
PACIFIC NORTHWEST AND THE SOUTHERN STREAM CLOSED LOW BREAKS DOWN
AS ENERGY EJECTS EASTWARD OVER THE SOUTHWEST/CALIFORNIA/BAJA
MID-PERIOD. DETERMINISTIC SOLUTIONS BEGIN TO DIVERGE A BIT MORE BY
WEDNESDAY. THE ECMWF HAS BEEN A BIT MORE CONSISTENT RUN-TO-RUN
WITH BOTH THE TIMING AND COMBINED PHASING OF THE STREAM ENERGIES,
WITH THE GFS NOTABLY MORE INCONSISTENT WITH BOTH THE EVOLUTION OF
THE NORTHERN AND SOUTHERN STREAM PHASING TOGETHER OVER THE CENTRAL
U.S., AS WELL AS WITH THE TIMING COMPARED TO THE ECMWF, WITH A
COMBINED SLOWER EASTWARD PROGRESSION. THE LATEST CMC DEPICTS
LINGERING SOUTHERN STREAM ENERGY OVER THE
SOUTHWEST/CALIFORNIA/BAJA, A MORE SPLIT-STREAM EVOLUTION THAN IN
THE GFS OR ECMWF. THE GEFS/ECENS MEANS NOTABLY LACK THE MORE
SUBTLE DETAILS OF THE STREAM ENERGIES PHASING, BUT THE MEAN TROUGH
AXIS IS GENERALLY SIMILAR TO THE ECWMF. THE MORE RECENT RUNS OF
THE GFS ARE ALSO A BIT MORE AMPLIFIED BOTH WITH THE TROUGH AND
SUBSEQUENT RIDGING UPSTREAM OVER THE WEST COAST COMPARED TO THE
ECMWF AND ENSEMBLE MEANS, AND WITH A DEEPER, CLOSED LOW DEVELOPING
AS THE STREAMS PHASE TOGETHER. THIS TRANSLATES INTO THURSDAY, WITH
THE GFS CONTINUING TO SHOW A TREND TOWARDS A DEEPER AND DEEPER
CLOSED LOW IN THE 00Z AND THEN 06Z RUN, WHILE THE ECMWF AND MEANS
REMAIN OPEN AND A BIT MORE PROGRESSIVE. TIMING WISE, BOTH THE GFS
AND ECMWF HAVE TRENDED SLOWER WITH THE EASTWARD PROGRESSION OF THE
SYSTEM, REGARDLESS OF THE EXACT EVOLUTION. THE AXIS OF MEAN
TROUGHING IN BOTH THE GEFS AND ECENS ONCE AGAIN TENDS TO ALIGN
MORE WITH THE ECMWF, AND BACKS THE TREND IN TIMING.
THE UPDATED WPC FORECAST BEGAN WITH A MULTI-MODEL BLEND GIVEN GOOD
OVERALL AGREEMENT ON THE PATTERN ACROSS THE CONUS AND WITH THE
NOTED UPSTREAM ENERGIES THROUGH THE EARLY TO MID-PERIOD. THE CMC
IS REMOVED FOR THE LATER PERIOD GIVEN THE TREND TOWARDS MORE
STREAM SEPARATION THAT WOULD BE OUT OF PHASE WITH THE OTHER
GUIDANCE. A CONTRIBUTION FROM THE ECENS AND GEFS MEANS IS INCLUDED
TO REPLACE THE CMC AND TIME-LIMITED UKMET WITH THE GREATEST
DETERMINISTIC CONTRIBUTION REMAINING FROM THE ECMWF AS IT ALIGNED
MOST CLOSELY WITH THE MEAN GUIDANCE. A SPLIT CONTRIBUTION FROM THE
00Z/06Z GFS IS USED TO CAPTURE THE NOTED TREND TOWARDS A MORE
AMPLIFIED TROUGH/RIDGE, AND DEEPENING CLOSED LOW, WITH A HIGHER
PRIORITY GIVEN TO THE 00Z RUN AS THIS TREND REMAINS AN OUTLIER
COMPARED TO THE ECMWF AND MEAN GUIDANCE. THE INCOMING 12Z GFS RUN
TRENDED AWAY FROM A DEEPER, CLOSED LOW AND TOWARDS A WEAKER, OPEN
WAVE GIVING MORE CONFIDENCE TO THE RELIANCE ON THE 00Z ECMWF, AND
00Z OVER THE 06Z GFS IN THE UPDATED FORECAST BLEND.
..WEATHER/HAZARDS HIGHLIGHTS
AS TROUGHING COMES INTO THE WEST EARLY NEXT WEEK, PRECIPITATION
WILL SPREAD INTO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES ON
SUNDAY AND MONDAY, 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, A
MARGINAL RISK HAS BEEN INCLUDED FOR 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 WILL THEN SPREAD
INTO INTERIOR PARTS OF THE WEST MONDAY-TUESDAY. ADDITIONAL
MOISTURE AHEAD OF ANOTHER SYSTEM UPSTREAM OVER THE PACIFIC WILL
CONTINUE PRECIPITATION CHANCES IN THE PACIFIC NORTHWEST THROUGH
WEDNESDAY-THURSDAY. THE HIGHEST LIKELIHOOD FOR WINTER-RELATED
IMPACTS IS IN THE CASCADES, SIERRA, AND PORTIONS OF THE
NORTHERN/CENTRAL ROCKIES, THOUGH MOST OF THE REGIONAL HIGHER
ELEVATION MOUNTAIN RANGES WILL AT LEAST SEE SOME SNOW THROUGH THE
PERIOD. WIDESPREAD STRONG, GUSTY WINDS ARE ALSO EXPECTED ACROSS
MUCH OF THE WEST, PARTICULARLY FOR HIGHER ELEVATIONS, AS A COUPLE
FRONTAL SYSTEMS PASS THROUGH, LINGERING THE LONGEST ALONG THE
EASTERN RANGES/FOOTHILLS OF THE ROCKIES AND IMMEDIATE HIGH PLAINS.
FARTHER EAST, A COLD FRONT TRACKING THROUGH THE NORTHEASTERN U.S.
COULD LEAD TO SOME LIGHT SHOWERS ACROSS PORTIONS OF THE OHIO
VALLEY/APPALACHIANS INTO THE NORTHEAST SUNDAY, THOUGH MOST
LOCATIONS WILL LIKELY REMAIN DRY. PRECIPITATION CHANCES WILL BEGIN
TO INCREASE TUESDAY AND ESPECIALLY INTO WEDNESDAY ACROSS MUCH OF
THE EASTERN HALF OF THE COUNTRY AS MOIST SOUTHERLY FLOW INCREASES
AHEAD OF THE APPROACHING UPPER-LEVEL TROUGH AND SURFACE LOW
PRESSURE/FRONTAL SYSTEM FROM THE WEST. MOST PRECIPITATION WILL BE
IN THE FORM OF RAIN GIVEN ANOMALOUS WARMTH, BUT SOME SNOW ON THE
BACKSIDE OF THE LOW AND COLD FRONT FOR THE UPPER MIDWEST/GREAT
LAKES IS POSSIBLE WEDNESDAY, THOUGH CONFIDENCE IN THIS SCENARIO
REMAINS RATHER LOW. RAINFALL AMOUNTS COULD BE LOCALLY HEAVY,
PARTICULARLY FOR 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.
PUTNAM/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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