899
FXUS02 KWBC 301916
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
215 PM EST TUE JAN 30 2024
VALID 12Z FRI FEB 02 2024 - 12Z TUE FEB 06 2024
...LATE WEEK INTO WEEKEND SYSTEM TO SPREAD SIGNIFICANT
PRECIPITATION ACROSS MUCH OF THE WEST AND THEN THE PLAINS AND GULF
COAST/SOUTHEAST...
...ANOTHER STRONG WEATHER SYSTEM INCREASINGLY LIKELY TO IMPACT
CALIFORNIA BY EARLY NEXT WEEK...
..OVERVIEW
GUIDANCE CONTINUES TO SHOW AN EVOLVING OMEGA BLOCK PATTERN ALOFT,
WITH VARYING DEGREES OF MEAN TROUGHING ALONG OR OFFSHORE THE WEST
COAST AND OVER THE CANADIAN MARITIMES WHILE AN UPPER RIDGE
PREVAILS OVER THE UPPER MIDWEST/GREAT LAKES. THERE WILL BE THE
ADDED WRINKLE OF LATE WEEK WESTERN U.S. UPPER TROUGH ENERGY
BREAKING OFF AN UPPER LOW THAT TRACKS ACROSS THE SOUTHERN TIER
DURING THE WEEKEND INTO EARLY NEXT WEEK. THE LARGE SCALE PATTERN
WILL PROMOTE EPISODES OF SIGNIFICANT PRECIPITATION AND POTENTIALLY
OTHER ACTIVE WEATHER ACROSS THE WEST, FIRST THROUGH LATE WEEK AND
THEN RENEWED WITH HEAVY AMOUNTS INTO EARLY NEXT WEEK ESPECIALLY
ACROSS CALIFORNIA. THE SOUTH-CENTRAL TO SOUTHEASTERN U.S. WILL
ALSO SEE A THREAT FOR HEAVY RAIN OVER THE WEEKEND INTO EARLY NEXT
WEEK WITH THE UPPER LOW AND RELATED SURFACE LOW. MEANWHILE, THE
FORECAST PATTERN WOULD SUPPORT PERSISTENCE OF MUCH ABOVE NORMAL
TEMPERATURES OVER THE UPPER MIDWEST AND VICINITY IN CONTRAST TO
COOL DAYTIME HIGHS OVER THE SOUTHWEST/CALIFORNIA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW REASONABLY GOOD CONSENSUS ON THE
LARGE SCALE PATTERN BUT ONGOING SPREAD ON PLACEMENT/TIMING DETAILS
ON SURFACE AND UPPER-LEVEL FEATURES. THE FIRST SUCH FEATURE TO
CONSIDER IS TROUGHING ALOFT AND A SURFACE LOW OVER THE
NORTHEAST/CANADIAN MARITIMES LATE THIS WEEK INTO THE WEEKEND. THE
00Z CMC AND EC WERE ON THE EASTERN SIDE WITH THESE FEATURES
COMPARED TO THE GFS RUNS AND SOME OF THE EC-INITIALIZED MACHINE
LEARNING MODELS. 12Z GUIDANCE IS A BIT IN BETWEEN WITH THE TROUGH
AXIS, THOUGH THE 12Z GFS IS A LITTLE SOUTH.
UPSTREAM, ANOTHER CONSIDERATION OF THE FORECAST WILL BE THE
PRECISE LATITUDE AND SPEED OF THE UPPER LOW AND ASSOCIATED SURFACE
SYSTEM CROSSING THE SOUTHERN TIER BY SUNDAY AND BEYOND. THE 06Z
GFS SEEMED TO BE MOST CONSISTENT WITH THE OTHER GUIDANCE COMPARED
TO THE FARTHER EAST 00Z AND NOW 12Z RUNS. MEANWHILE THE 00Z CMC
WAS SLIGHTLY ON THE SLOW SIDE, WHILE ECMWF RUNS APPEAR TO BE A
GOOD MIDDLE GROUND, THOUGH THE NEWER 12Z RUN MAY STRAY A BIT SOUTH
BY MONDAY-TUESDAY IN THE WESTERN ATLANTIC. WHAT BECOMES OF THIS
SYSTEM UPON REACHING THE WESTERN ATLANTIC EARLY NEXT WEEK IS STILL
SOMEWHAT UNCERTAIN GIVEN THE SPREAD AND INCONSISTENCY FOR
TROUGHING TO THE NORTH.
NEAR THE WEST COAST, THERE IS REASONABLE AGREEMENT FOR A SURFACE
LOW TO TRACK SOUTHWARD JUST OFFSHORE IN THE EASTERN PACIFIC
FRIDAY-SATURDAY. THIS IS SUPPORTED BY AN UPPER LOW DROPPING SOUTH
THAT IS LIKELY TO GET REINFORCED BY ENERGY MOVING EASTWARD THROUGH
THE PACIFIC AND MOST LIKELY INTERACTING/JOINING BY SUNDAY. THE
ECMWF AND GFS SEEMED BEST ALIGNED WITH THE ENSEMBLES ON THIS. THE
00Z CMC ON THE OTHER HAND SHOWED LESS PHASING ALOFT AND THUS HAS
AN UPPER LOW DISPLACED TO THE WEST, WHILE THE UKMET INDICATES
ADDITIONAL ENERGY FROM THE NORTHEAST PACIFIC COMING SOUTHWARD TO
ENHANCE THE PREEXISTING UPPER LOW, LEAVING THE CENTROID OF THE LOW
ON THE NORTHERN SIDE. AT THE SURFACE THERE IS ALSO SPREAD IN
POSITION AND DEPTH OF THE LOW. THE 00Z ECMWF TRENDED WEAKER, BUT
THE 12Z IS NOW STRONGER. GFS RUNS HAVE STAYED MAINLY STRONG BUT
HAVE POSITION DIFFERENCES.
CONSIDERING THESE FACTORS, THE WPC FORECAST FAVORED THE 06Z GFS
AND 00Z ECMWF HEAVILY EARLY IN THE PERIOD, AND THEN GRADUALLY
TRANSITIONED TO HALF GEFS AND EC ENSEMBLE MEANS BY DAY 6 AND MORE
BY DAY 7 AS INDIVIDUAL MODELS INCREASED SPREAD. THIS MAINTAINED
REASONABLY GOOD CONSISTENCY WITH THE PREVIOUS FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
THE LEADING UPPER TROUGH MOVING INTO THE WEST WILL PRODUCE A BROAD
AREA OF RAIN AND HIGHER ELEVATION SNOW, WITH SIGNIFICANT
ACCUMULATIONS POSSIBLE FRIDAY-SATURDAY OVER MUCH OF THE NORTHERN
AND CENTRAL ROCKIES. THERE WILL ALSO BE SOME LINGERING
PRECIPITATION CLOSER TO THE WEST COAST DURING THAT TIME. THE UPPER
LOW BREAKING OFF FROM THE SOUTHERN PART OF THE TROUGH ALONG WITH
THE ASSOCIATED SURFACE SYSTEM MAY LEAD TO A PERIOD OF EASTERLY
PRECIPITATION ENHANCEMENT ALONG THE CENTRAL ROCKIES, WHILE SOME
SNOW IS POSSIBLE FARTHER EAST INTO THE NORTH-CENTRAL HIGH PLAINS
THIS WEEKEND, BUT WITH AMPLE UNCERTAINTY IN THE DETAILS. THE UPPER
LOW SHOULD BEGIN TO GENERATE RAIN AND THUNDERSTORMS OVER THE
SOUTHERN PLAINS BY FRIDAY OR FRIDAY NIGHT WITH LIGHTER TOTALS
EXTENDING INTO THE CENTRAL PLAINS. THE DAY 4 EXCESSIVE RAINFALL
OUTLOOK COVERING FRIDAY-FRIDAY NIGHT MAINTAINS THE MARGINAL RISK
ACROSS THE EASTERN HALF OF TEXAS INTO PARTS OF OKLAHOMA, WITH
GUIDANCE CONTINUING TO SIGNAL POTENTIAL FOR LOCALLY HEAVY (THOUGH
NOT EXCEPTIONAL) RAINFALL, WITH SOME EXPANSION TO THE GULF COAST
AS INSTABILITY MAY BE MAXIMIZED THERE FOR HEAVY RAINFALL RATES
POSSIBLY ACROSS URBAN AREAS. THEN THE EASTWARD PROGRESSION OF THE
SYSTEM OVER THE WEEKEND WILL SPREAD SOME HEAVY RAINFALL ACROSS THE
GULF COAST STATES AND SOUTHEAST. THE DAY 5 ERO DEPICTS A SLIGHT
RISK AREA ALONG THE CENTRAL GULF COAST WHERE THE BEST INSTABILITY
AND ENSEMBLE PROBABILITIES OF HIGHEST RAINFALL TOTALS OVERLAP,
WITH OPERATIONAL MODEL RUNS SHOWING HEAVY RAINFALL POTENTIAL AS
WELL, LIKELY IN THE FORM OF A SQUALL LINE MARCHING EASTWARD WITH
HIGH RAINFALL RATES. THE SURROUNDING MARGINAL RISK AREA EXTENDS
NORTH-NORTHWEST INTO SOUTHWESTERN MISSOURI AND SOUTHEASTERN
KANSAS, FOR SOMEWHAT LOWER RAINFALL TOTALS BUT WITH GROUND
CONDITIONS STARTING OUT ON THE DAMP SIDE. THERE IS SOME INCREASING
CONCERN FOR A SECONDARY MAXIMUM OF HEAVY RAINFALL AROUND ARKANSAS,
INTO WHICH A TONGUE OF INSTABILITY STRETCHES AND THE FRONT/SURFACE
LOW TRACK SHOULD BE SLOWER MOVING FOR MANY HOURS OF CONVECTION,
WHICH COULD PRODUCE FLOODING ISSUES CONSIDERING THOSE WET
ANTECEDENT CONDITIONS. THUS WILL CONTINUE TO MONITOR IF AN
EXPANSION TO THE SLIGHT RISK FARTHER NORTH IS NEEDED. HEAVY
RAINFALL POTENTIAL SHOULD CONTINUE EASTWARD INTO THE
SOUTHEAST/CAROLINAS BY EARLY NEXT WEEK.
THE DETAILS REMAIN VERY UNCERTAIN BUT THE OVERALL FORECAST PATTERN
CONTINUES TO SHOW THE POTENTIAL FOR A SIGNIFICANT ATMOSPHERIC
RIVER EVENT TO AFFECT CALIFORNIA FROM AROUND SUNDAY INTO THE EARLY
PART OF THE WORKWEEK. GUSTY WINDS MAY ACCOMPANY THE ASSOCIATED
SURFACE LOW, ESPECIALLY IF IT ENDS UP ON THE STRONGER SIDE OF THE
GUIDANCE ENVELOPE. THIS EVENT STILL APPEARS LIKELY TO PRODUCE
GREATER LOW ELEVATION RAIN/MOUNTAIN SNOW TOTALS THAN THE PRECEDING
EVENT DUE TO A LONGER DURATION OF SOUTHWESTERLY FLOW ALOFT AND A
MORE DIRECT CONNECTION WITH LOWER LATITUDE MOISTURE. CONTINUE TO
MONITOR FORECASTS FOR THIS TIME FRAME AS SPECIFICS GRADUALLY
BECOME BETTER RESOLVED.
THE PERSISTENT UPPER RIDGE OVER AND NEAR THE UPPER MIDWEST WILL
SUPPORT A CORE OF PERSISTENTLY WELL ABOVE NORMAL TEMPERATURES OVER
THAT PART OF THE COUNTRY. RECENT GUIDANCE ADJUSTMENTS FOR
SPECIFICS OF THE UPPER PATTERN HAVE INCREASED POTENTIAL
TEMPERATURE ANOMALIES, WITH MORNING LOWS POSSIBLY AS WARM AS
25-35F ABOVE NORMAL EXCEEDING DAILY RECORDS FOR MULTIPLE DAYS.
EXPECT DAYTIME HIGHS TO BE LESS EXTREME, UP TO 15-25F ABOVE
NORMAL. SOME OF THIS WARMTH, ESPECIALLY FOR MORNING LOWS, WILL
EXTEND ACROSS A MUCH BROADER AREA BETWEEN THE ROCKIES AND
APPALACHIANS. IN CONTRAST, THE SOUTHWEST U.S./CALIFORNIA SHOULD
SEE COOL DAYTIME HIGHS THROUGH THE PERIOD WITH SOME LOCATIONS UP
TO 10-15F BELOW NORMAL. CLOUDS/PRECIPITATION OVER THE WEST SHOULD
KEEP MORNING LOWS NEAR TO ABOVE NORMAL.
TATE/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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