036
FXUS02 KWBC 010700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST FRI MAR 01 2024
VALID 12Z MON MAR 04 2024 - 12Z FRI MAR 08 2024
..WET PATTERN FOR PARTS OF THE WEST COAST AND THE SOUTH
..OVERVIEW
LATEST GUIDANCE FOR NEXT WEEK GENERALLY AGREES UPON LARGE SCALE
MEAN TROUGHING OVER THE WESTERN HALF OF THE LOWER 48 AND UPPER
RIDGING OFF THE EAST COAST. THIS PATTERN WILL FAVOR COOL
CONDITIONS OVER THE WEST WITH PERIODS OF ENHANCED PRECIPITATION
OVER SOME AREAS, WHILE ABOVE NORMAL TEMPERATURES PREVAIL FARTHER
EAST WITH THE LOWER MISSISSIPPI VALLEY INTO SOUTHEAST SEEING THE
POTENTIAL FOR SOME HEAVY RAINFALL. RAIN MAY EXTEND FARTHER NORTH
ACROSS THE EASTERN HALF OF THE COUNTRY AS WELL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
WHILE MODELS AND ENSEMBLES ARE SIMILAR FOR THE VERY LARGE SCALE
PATTERN, THERE ARE SIGNIFICANT EMBEDDED DIFFERENCES THAT AFFECT
THE FORECAST OVER SOME AREAS. ALREADY EARLY IN THE WEEK THE
GUIDANCE ESSENTIALLY SORTS ITSELF INTO TWO CLUSTERS, WITH THE
GFS/GEFS RUNS SHOWING BROADER AND MORE AMPLIFIED UPPER TROUGHING
OVER THE WESTERN HALF OF THE COUNTRY VERSUS OTHER SOLUTIONS THAT
SHOW FLATTER INTERIOR WEST/ROCKIES FLOW BETWEEN A SHORTWAVE
REACHING VANCOUVER ISLAND AND THE CANADIAN SYSTEM JUST NORTH OF
THE PLAINS/UPPER MIDWEST. 12Z ECMWF-INITIALIZED MACHINE LEARNING
MODELS FAVORED THE MAJORITY ECMWF CLUSTER. PRIMARY RESULTS OF
LEANING AWAY FROM THE GFS SCENARIO FOR THIS PART OF THE FORECAST
WERE SOMEWHAT GREATER PRECIPITATION POTENTIAL ALONG THE
NORTH-CENTRAL WEST COAST VERSUS GFS FORECASTS, ALONG WITH WEAKER
SURFACE WAVINESS OVER THE MIDWEST/GREAT LAKES. AT LEAST THE NEW
00Z GFS HAS TONED DOWN ITS MIDWEST WAVE VERSUS THE 12Z/18Z RUNS.
THROUGH THE REST OF THE WEEK THERE ARE A LOT OF SHORTWAVE
DIFFERENCES ACROSS THE NORTHERN TIER WITHIN A GENERAL THEME OF
ENOUGH DYNAMICS EXISTING TO SUPPORT SOME DEGREE OF SURFACE FRONTAL
EVOLUTION, WHILE ONE OR MORE PACIFIC SHORTWAVES SHOULD
AMPLIFY/MOVE INTO THE WEST AFTER MIDWEEK, LIKELY SUPPORTING A
WELL-DEFINED SURFACE SYSTEM THAT MAY REACH THE PLAINS BY NEXT
FRIDAY. INDIVIDUAL ENSEMBLE MEMBERS AND ML MODELS VARY
CONSIDERABLY FOR THE TIMING OF UPSTREAM PACIFIC FLOW BY LATE NEXT
WEEK WHILE GENERALLY SUGGESTING THAT THE TROUGH MOVING THROUGH THE
WEST (AND ASSOCIATED LEADING SURFACE SYSTEM) COULD END UP BEING
SOMEWHAT FASTER THAN THE CURRENT MODEL/ENSEMBLE MEAN MAJORITY.
FARTHER EAST, THE 12Z ECMWF HAS MINIMAL SUPPORT FROM OTHER
GUIDANCE FOR ITS SLOW UPPER LOW THAT DEVELOPS. INSTEAD A MORE
PROGRESSIVE UPPER TROUGH/SURFACE REFLECTION APPEARS TO BE THE MORE
LIKELY SCENARIO.
THE EARLY PART OF THE FORECAST STARTED WITH PRIMARY EMPHASIS ON
THE 12Z ECMWF/UKMET/CMC WITH MINORITY INPUT OF THE 18Z GEFS WHICH
WAS A BIT LESS EXTREME THAN THE GFS FOR THE PATTERN OVER THE
WESTERN HALF OF THE COUNTRY. LATER ON THE FAVORED BLEND RAPIDLY
INCREASED 18Z GEFS/12Z ECENS INPUT TO 50-60 PERCENT TOTAL WEIGHT
WHILE REINCORPORATING A LITTLE 18Z/12Z GFS AND REDUCING 12Z ECMWF
INFLUENCE. THIS APPROACH EMPHASIZED WHAT SIMILARITIES EXISTED
FROM THE LARGE SCALE PERSPECTIVE AND MAINTAINED A REASONABLE
DEGREE OF CONTINUITY WHERE FEASIBLE.
..WEATHER/HAZARDS HIGHLIGHTS
DURING THE FIRST HALF OF THE WEEK EXPECT A FRONT LINGERING
OVER/NEAR THE GULF COAST TO PROVIDE A FOCUS FOR RAIN AND
THUNDERSTORMS THAT MAY EXTEND ALONG AND NORTH OF THE GULF COAST,
WITH A FRONT DROPPING SOUTHEASTWARD FROM THE CENTRAL U.S. ALSO
POSSIBLY ENHANCING GULF INFLOW SOMEWHAT TOWARD MIDWEEK. THE DAY 4
EXCESSIVE RAINFALL OUTLOOK VALID MONDAY REFLECTS A MARGINAL RISK
AREA CENTERED OVER THE LOWER MISSISSIPPI VALLEY WHILE THE DAY 5
MARGINAL RISK AREA REFLECTS THE CONSENSUS EASTWARD PROGRESSION OF
HEAVIEST RAINFALL POTENTIAL TOWARD THE SOUTHEAST (WHILE STILL
POSSIBLY LINGERING OVER THE CENTRAL GULF COAST REGION). EXPECT
SOME RAINFALL TO EXTEND FARTHER NORTH ALONG THE ADVANCING CENTRAL
U.S. FRONT AS WELL. FROM MIDWEEK ONWARD THE MID-ATLANTIC AND
NORTHEAST MAY BECOME THE MOST FAVORED REGION FOR MEANINGFUL
RAINFALL AS THE WAVY FRONT PROGRESSES EASTWARD. MEANWHILE, UPPER
LEVEL AND SURFACE SYSTEMS WILL PROMOTE EPISODES OF RAIN AND HIGHER
ELEVATION SNOW OVER THE WEST WITH GUIDANCE DIFFERENCES KEEPING
CONFIDENCE LOWER THAN DESIRED FOR THE DETAILS. THE NON-GFS
MAJORITY CLUSTER WOULD HAVE AN EARLY WEEK SYSTEM FOCUSING A NARROW
AXIS OF ENHANCED MOISTURE AIMED AT THE WEST COAST NEAR THE
CALIFORNIA/OREGON BORDER. THE ECMWF/ECENS MEAN STILL DEPICT
FAIRLY MODEST MOISTURE ANOMALIES WITH THIS EVENT WHOSE HEAVY
RAINFALL MAY BE FAIRLY LOCALIZED, SO HAVE OPTED NOT TO DEPICT ANY
RISK AREA IN THE DAY 4 ERO FOR NOW. A MID-LATE WEEK SYSTEM MAY
BRING ADDITIONAL RAIN/SNOW TO THE WEST. HOW QUICKLY THIS SYSTEM
PROGRESSES THROUGH THE WEST WILL DETERMINE WHETHER A REBOUND IN
RAINFALL COULD OCCUR ALONG/NORTH OF THE GULF COAST LATE IN THE
WEEK.
UNDER THE INFLUENCE OF MEAN TROUGHING ALOFT, MOST AREAS FROM THE
WEST COAST INTO THE ROCKIES WILL SEE HIGHS 5-15F BELOW NORMAL
WHILE MORNING LOWS WILL TEND TO BE NEAR OR SLIGHTLY BELOW NORMAL.
IN CONTRAST, EXPECT WELL ABOVE NORMAL TEMPERATURES TO PREVAIL OVER
THE EASTERN HALF OR SO OF THE COUNTRY. PLUS 20-30F ANOMALIES WILL
BE POSSIBLE FROM THE CENTRAL-SOUTHERN PLAINS INTO THE NORTHEAST
EARLY-MID WEEK WITH LOCATIONS FROM THE MIDWEST INTO NORTHEAST
SEEING THE BEST POTENTIAL FOR SOME DAILY RECORDS.
RAUSCH
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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