265
FXUS02 KWBC 310700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST WED JAN 31 2024
VALID 12Z SAT FEB 03 2024 - 12Z WED FEB 07 2024
...SYSTEM EMERGING FROM THE WEST TO SPREAD SIGNIFICANT
PRECIPITATION ACROSS THE NORTHERN-CENTRAL ROCKIES PLUS THE PLAINS
AND GULF COAST/SOUTHEAST THROUGH THE WEEKEND...
...ANOTHER STRONG WEATHER SYSTEM INCREASINGLY LIKELY TO IMPACT
CALIFORNIA BY EARLY NEXT WEEK...
..OVERVIEW
LATEST GUIDANCE CONTINUES TO SHOW AN ACTIVE WEATHER PATTERN FOR
THE WEST FOR THE FIRST HALF OF NEXT WEEK. INITIAL UPPER TROUGHING
NEAR THE PACIFIC NORTHWEST SHOULD INTERACT WITH AN INCOMING
SOUTHERN STREAM SYSTEM TO PRODUCE A LARGE SCALE POSITIVELY TILTED
MEAN TROUGH THAT WILL PROMOTE A STRONG SOUTHWESTERLY FLOW OF
MOISTURE INTO THE WEST OVER A MULTI-DAY TIME FRAME, WITH HEAVIEST
RAIN/MOUNTAIN SNOW LIKELY TO FOCUS OVER CALIFORNIA. MEANWHILE AN
UPPER LOW TRACKING FROM THE SOUTHERN HALF OF THE ROCKIES THROUGH
THE SOUTHEAST DURING THE WEEKEND AND EARLY NEXT WEEK WILL SUPPORT
A STRONG SURFACE SYSTEM AND A HEAVY RAINFALL THREAT ACROSS THE
SOUTHERN TIER. MEANWHILE A STRONG UPPER RIDGE CENTERED OVER THE
UPPER MIDWEST/GREAT LAKES FROM THE WEEKEND INTO MONDAY SHOULD
MERGE WITH ANOTHER RIDGE BUILDING IN ACROSS THE SOUTHWEST TO YIELD
A SOUTHERN PLAINS INTO NORTHEAST RIDGE BY NEXT WEDNESDAY. THESE
RIDGES WILL SUPPORT WELL ABOVE NORMAL TEMPERATURES OVER MUCH OF
THE CENTRAL U.S. THE RIDGE THAT EVENTUALLY REACH THE NORTHEAST BY
WEDNESDAY WILL DISPLACE A CANADIAN MARITIMES UPPER TROUGH/LOW THAT
WILL PROMOTE NORTHWESTERLY FLOW ALOFT OVER THE NORTHEAST FROM THE
WEEKEND INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
PREFERENCES BASED ON 12Z/18Z GUIDANCE LED TO A STARTING BLEND
EARLY IN THE PERIOD CONSISTING OF AN OPERATIONAL MODEL COMPOSITE
(SOMEWHAT MORE GFS/ECMWF THAN UKMET/CMC), FOLLOWED BY A TREND
TOWARD HALF 18Z GEFS/12Z ECENS MEANS AND MORE LINGERING 12Z ECMWF
WEIGHT THAN GFS/CMC. PRIMARY LARGE SCALE CONSIDERATIONS WERE THAT
GFS HANDLING OF ENERGY DROPPING INTO THE WEST COAST UPPER TROUGH
LATE IN THE PERIOD BECAME INCREASINGLY UNSUPPORTED BY OTHER
GUIDANCE, WHILE THE 12Z CMC STRAYED NORTH WITH THE SOUTHEAST
SYSTEM ONCE REACHING THE WESTERN ATLANTIC. IN THE NEW 00Z RUNS,
THE CMC SHOWS LESS PHASING ALOFT NEAR THE WEST COAST THAN MOST
OTHER SOLUTIONS--KEEPING THE SURFACE SYSTEM FARTHER OFFSHORE THAN
MODEL/ENSEMBLE CONSENSUS--AND NOW THE 00Z GFS STRAYS NORTHWARD
WITH THE WESTERN ATLANTIC SYSTEM LATE.
..WEATHER/HAZARDS HIGHLIGHTS
UPPER TROUGH ENERGY OVER THE WEST/ROCKIES TO BEGIN THE WEEKEND
WILL PRODUCE A BROAD AREA OF MODERATE TO HEAVY SNOW OVER MUCH OF
THE NORTHERN-CENTRAL ROCKIES ON SATURDAY WITH LIGHTER ACTIVITY
LINGERING INTO SUNDAY. PRECIPITATION OVER THE HIGH PLAINS MAY FALL
AS RAIN AND/OR SNOW DEPENDING ON LOCATION, WITH RELATIVELY BETTER
POTENTIAL FOR SOME MEANINGFUL SNOW OVER PARTS OF THE
CENTRAL/NORTH-CENTRAL HIGH PLAINS. 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 AS WELL. RAIN NORTH AND THUNDERSTORMS
FARTHER SOUTH SHOULD ALREADY BE IN PROGRESS FROM THE CENTRAL
PLAINS SOUTH-SOUTHEAST TO THE GULF COAST AS OF EARLY SATURDAY,
WITH EASTWARD PROGRESSION OF THE SYSTEM OVER THE WEEKEND SPREADING
SOME HEAVY RAINFALL ACROSS THE GULF COAST STATES AND SOUTHEAST.
THE DAY 4 EXCESSIVE RAINFALL OUTLOOK VALID SATURDAY-SATURDAY NIGHT
MAINTAINS 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 ONLY ADJUSTMENT
FROM CONTINUITY WAS TO EXPAND THE WESTERN END OF THE SLIGHT RISK
AREA PER LATEST GUIDANCE TRENDS. THE SURROUNDING MARGINAL RISK
AREA EXTENDS NORTH-NORTHWEST INTO SOUTHWESTERN MISSOURI AND
EASTERN 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. THIS SIGNAL PERSISTS BUT NOT AGREEABLY
ENOUGH YET TO EXPAND THE SLIGHT RISK INTO THIS REGION. THUS WILL
CONTINUE TO MONITOR GOING FORWARD TO SEE IF THIS EXPANSION MAY
ULTIMATELY BE NEEDED. HEAVY RAINFALL POTENTIAL SHOULD CONTINUE
EASTWARD INTO THE SOUTHEAST/CAROLINAS BY SUNDAY-MONDAY. THE NEW
DAY 5 ERO DEPICTS A BROAD MARGINAL RISK AREA OVER THE SOUTHEAST,
WITH CURRENT SIGNALS SOMEWHAT DIFFUSE FOR WHERE BEST RAINFALL
FOCUS WILL BE. ONE REGION OF POTENTIALLY GREATER INTEREST MAY BE
OVER PARTS OF GEORGIA/SOUTH CAROLINA WHICH WILL BE JUST TO THE
NORTH OF ONE OR MORE FRONTS THAT COULD HELP TO FOCUS HEAVIER
RAINFALL, WITH AT LEAST THE ECMWF SHOWING SOME INSTABILITY
CROSSING THIS AREA AS WELL. SOME HEAVY RAINFALL COULD LINGERING
INTO MONDAY OVER OR NEAR THE CAROLINAS, WHILE DEPARTURE OF THE
SURFACE SYSTEM MAY LEAD TO A PERIOD OF STRONG WINDS ALONG/OFFSHORE
THE SOUTHEAST COAST.
WHILE SPECIFICS ARE STILL NOT UNANIMOUS IN THE GUIDANCE, THE
MAJORITY OF GUIDANCE SUGGESTS STEADILY INCREASING CONFIDENCE IN A
MULTI-DAY ATMOSPHERIC RIVER EVENT AFFECTING CALIFORNIA FROM AROUND
SUNDAY INTO THE NEXT WORKWEEK. A POTENTIALLY STRONG SYSTEM THAT
MAY PRODUCE GUSTY WINDS SHOULD TRACK TO A POSITION JUST OFFSHORE
NORTHERN CALIFORNIA BY EARLY MONDAY, WOULD BRING THE LEADING SURGE
OF MOISTURE. SLOW MOVEMENT OF THE SUPPORTING UPPER TROUGH MAY
PRODUCE A CONTINUED SOUTHWESTERLY FLOW OF MOISTURE INTO THE REGION
THROUGH AT LEAST TUESDAY (WITH PRECIPITATION ENHANCEMENT POSSIBLY
GENERATED BY ONE OR MORE TRAILING FRONTAL WAVES) WHILE THE LEADING
EDGE OF THE MOISTURE BEGINS TO PUSH INTO THE SOUTHWEST/GREAT
BASIN. FOLLOWING THE GUIDANCE MAJORITY THAT BRINGS IN MOISTURE
EARLIER THAN THE 00Z CMC, THE NEW DAY 5 ERO PLANS TO INTRODUCE A
SLIGHT RISK AREA ALONG COASTAL CALIFORNIA FROM NEAR MONTEREY
SOUTHWARD TO/NEAR THE TRANSVERSE RANGES. THE SURROUNDING MARGINAL
RISK EXTENDS INTO PARTS OF NORTHERN CALIFORNIA. 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 UPPER RIDGE INITIALLY OVER AND NEAR THE UPPER MIDWEST AND THEN
BECOMING ALIGNED FROM FROM THE SOUTHERN PLAINS THROUGH GREAT LAKES
WILL SUPPORT A BROAD AREA OF UNSEASONABLY WARM TEMPERATURES OVER
THE CENTRAL U.S. THROUGH THE PERIOD. CONTINUE TO EXPECT THE
GREATEST ANOMALIES TO BE OVER/NEAR THE UPPER MIDWEST WHERE MORNING
LOWS MAY BE AS WARM AS 25-35F ABOVE NORMAL AND EXCEEDING DAILY
RECORDS FOR MULTIPLE DAYS, WHILE DAYTIME HIGHS SHOULD BE A LITTLE
LESS EXTREME, UP TO 15-25F ABOVE NORMAL. IN CONTRAST, THE
SOUTHWEST U.S./CALIFORNIA SHOULD SEE COOL DAYTIME HIGHS THROUGH
THE PERIOD WITH SOME LOCALIZED AREAS UP TO 10-15F BELOW NORMAL.
CLOUDS/PRECIPITATION OVER THE WEST SHOULD KEEP MORNING LOWS NEAR
TO ABOVE NORMAL. FLORIDA SHOULD SEE A COUPLE COOL DAYS WITH HIGHS
5-10F BELOW NORMAL BY TUESDAY-WEDNESDAY AFTER PASSAGE OF THE
SOUTHEAST SYSTEM.
RAUSCH/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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