415
FXUS02 KWBC 280700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST WED FEB 28 2024
VALID 12Z SAT MAR 02 2024 - 12Z WED MAR 06 2024
...HEAVY SNOW AND HIGH WIND THREAT FOR THE WESTERN AND
NORTH-CENTRAL U.S...
..WET PATTERN FOR THE WEST COAST AND THE SOUTH
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GFS/ECMWF/UKMET/CANADIAN MODEL GUIDANCE SOLUTIONS SEEM
REASONABLY WELL CLUSTERED FOR SATURDAY OVER THE CONUS AND VICINITY
INCLUDING MAIN DEPCITIONS OF A HIGHLY AMPLIFIED UPPER TROUGH
WORKING INTO THE WEST COAST AND A FAR DOWNSTREAM SOUTHERN STREAM
SYSTEM FINALLY EJECTING OFF THE EAST COAST. A MODEL COMPOSITE
LOOKS REASONABLE. HOWEVER, MODEL SOLUTIONS QUICKLY DIVERGE SUNDAY
WITH THE HANDLING OF DYNAMIC SHORTWAVES DIGGING INTO AND ROTATING
THROUGH AN AMPLFIED MEAN UPPER TROUGH POSITION SLATED TO SHIFT
THROUGH THE WEST TO THE CENTRAL U.S. INTO EARLY-MID NEXT WEEK.
MODEL CYCLE TO CYCLE CONTINUITY AND FORECAST CONFIDENCE HAS
DECREASED FROM YESTERDAY WITH THE AMPLITUDE AND TIMINGS OF THESE
LOCAL WEATHER/HAZARD FOCUSING SYSTEMS, ALBEIT STILL EMBEDDED
WITHIN AN ACTIVE AND DYNAMIC UPPER FLOW PATTERN EVOLUTION.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED
FROM A GEFS/ECMWF ENSEMBLE MEAN COMPOSITE ALONG WITH THE
COMPATIBLE NATIONAL BLEND OF MODELS TO ISOLATE, MAINTAIN AND
DEPICT THE MOST PREDICTABLE FORECAST COMPONENTS AT THESE LONGER
TIME FRAMES. WPC PRODUCT CONTINUITY WAS BEST MAINTAINED IN THIS
MANNER.
..OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
THE MAIN WEATHER STORY CONCERNS THE EVOLTION OF AMPLIFIED UPPER
TROUGHING SET TO DIG INTO THE EASTERN PACIFIC LATER THIS WEEK AND
THEN SHIFT EARNESTLY OVER THE WEST THIS WEEKEND. THIS AND
SUBSEQUENT BUT UNCERTAIN ADDITIONAL/VARIED PACIFIC SYSTEMS WILL
SUPPORT MULTIPLE CHANCES FOR LOCALLY MODERATE PRECIPITATION FOCI
INTO THE PACIFIC NORTHWEST OVER THIS FORECAST PERIOD. A LEADING
LONG FETCH MOISTURE PLUME/ATMOSPHERIC RIVER WILL SHIFT DOWN THE
COAST THROUGH SOUTHERN CALIFORNIA INTO SATURDAY WHILE EASING. THE
WPC DAY 4/SATURDAY EXCESSIVE RAINFALL OUTLOOK SHOWS A MARGINAL
RISK AREA. THERE IS ALSO A SIGNIFICANT THREAT FOR HIGH WINDS AND
VERY HEAVY SNOW TO SPREAD INLAND ACROSS THE INTERMOUNTAIN WEST AND
ROCKIES, ESPECIALLY FOR FAVORED TERRAIN/MOUNTAINS AS HIGHLIGHTED
IN THE WPC WINTER WEATHER OUTLOOK (WWO). CONFIDENCE CONTINUES TO
INCREASE IN THE RISK FOR MODERATE TO EXTREMELY DISRUPTIVE HIGH
SNOWFALL RATES/BLOWING SNOW, PARTICULARLY FOR THE SIERRA NEVADA.
ADDITIONALLY, VALLEY SNOWFALLS MAY DEVELOP MORE OVER TIME AS SNOW
LEVELS DECREASE WITH UPPER SYSTEM AND WAVY FRONTAL PUSH. THIS
TRANSLATION SHOULD ALSO FAVOR DEVELOPMENT OF AN EMERGING
PRECIPITATION SHIELD OVER THE COOLING ROCKIES/PLAINS BY
SUNDAY/MONDAY WITH PLAINS CYCLO/FRONTO GENESIS. THIS MAY LEAD INTO
A CHANCE FOR HEAVY WRAP-BACK SNOWS IN QUITE WINDY FLOW ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST WITH PLAINS CYCLOGENSIS AND THE
DIGGING OF COLD CANADIAN AIR SOUTHWARD IN THE WAKE OF THIS MAIN
SYSTEM, AS PER THE WWO. DOWNSTREAM, WIDESPREAD
SHOWERS/THUNDERSTORMS LOOK TO DEVELOP ACROSS THE
PLAINS/MISSISSIPPI VALLEY THEN EAST-CENTRAL U.S., WITH EVENTUAL
POSSIBLE FOCUS OVER VICINITY OF THE GULF COAST STATES INTO
TUESDAY/WEDNESDAY.
A LEADING SOUTHERN STREAM UPPER TROUGH WILL FINALLY EXIT THE EAST
COAST SATURDAY TO PROMPT MODEST/UNCERTAIN COASTAL FRONTAL LOWS,
WITH A WAVY TRAILING FRONT WITH CONTINUED RAIN/SHOWERS LINGERING
BACK ACROSS THE SOUTHEAST AND THE GULF OF MEXICO. UNCERTAIN BUT
GRADUALLY IMPROVING MOISTURE RETURN FROM THE GULF OF MEXICO AND
LINGERING ONSHORE FETCH FROM THE ATLANTIC MAY AGAIN COMBINE TO
FUEL RENEWED AREAS WITH ENHANCED RAIN/CONVECTIVE CHANCES BROADLY
OVER THE SOUTH TO MONITOR FOR ANY LOCAL RUNOFF ISSUES EARLY NEXT
WEEK WITH DOWNSTREAM PROGRESSION AND DIRECTION OF THE ACTIVE UPPER
FLOW PATTERN OUT FROM THE WEST
PACIFIC UPPER TROUGH AMPLIFICATION AND INLAND PROGRESSION THIS
WEEKEND WILL COOL TEMPERATURES OVER MUCH OF THE WEST, LEADING TO
THE SPREADING OF VALUES AS COLD AS 15 DEGREES BELOW NORMAL.
DOWNSTREAM, EXPECT MUCH ABOVE NORMAL PRE-FRONTAL WARMTH LATER WEEK
OVER THE NORTH-CENTRAL U.S. THAT WILL SPREAD TO MUCH OF THE
CENTRAL AND EASTERN U.S. THIS WEEKEND/EARLY NEXT WEEK DOWNSTREAM
OF THE MAIN UPPER TROUGH POSITION AND ASSOCIATED FRONTAL SYSTEMS.
PRE-FRONTAL SPRINGLIKE CONDITIONS FOR MUCH OF THE CENTRAL TO
EASTERN U.S. WILL FEATURE MINIMUM AND MAXIMUM TEMPERATURES RANGING
UPWARDS TO 20-30+ DEGREES ABOVE NORMAL OVER THE MIDWEST/GREAT
LAKES TO AGAIN CHALLENGE RECORD VALUES.
SCHICHTEL
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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