666
FXUS02 KWBC 210710
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 AM EST SUN JAN 21 2024
VALID 12Z WED JAN 24 2024 - 12Z SUN JAN 28 2024
...MULTI-DAY EXCESSIVE RAINFALL/FLOODING THREAT FROM SOUTHEAST
TEXAS TO THE LOWER MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST
STATES THIS WEEK...
..OVERVIEW
GUIDANCE STILL OVERALL AGREES THAT THE LARGE SCALE PATTERN ALOFT
THIS WEEK WILL SHIFT NOTABLY FROM THE ONGOING FRIGID PATTERN, AS A
RIDGE SHIFTS FROM THE CENTRAL U.S. INTO THE EAST COAST AND
TROUGHING BECOMES ESTABLISHED AND WORKS SLOWLY FROM THE THE
WESTERN TO THE CENTRAL U.S.. THIS WILL CHANNEL MOISTURE RETURN
FROM THE GULF OF MEXICO, WITH WARMING TEMPERATURES IN THE EASTERN
HALF OF THE COUNTRY. A SERIES OF DEEPENED PACIFIC SYSTEMS WILL
PERIODICALLY FOCUS LEAD FLOW/PRECIPITATION INLAND INTO THE PACIFIC
NORTHWEST BEFORE DIGGING INTO A MEAN WESTERN U.S. TROUGH IN
UNSETTLED/COOLED FLOW. MEANWHILE DOWNSTREAM, A SIGNIFICANT
RAINFALL EVENT REMAINS LOOMING AS MULTIPLE DAYS OF HEAVY RAIN AND
RUNOFF THREATS ARE EXPECTED AMID THE STALLING UPPER FLOW MEAN
PATTERN, WITH PRIMARY FOCUS FROM SOUTHEAST TEXAS THROUGH THE LOWER
MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES. FAVORABLE
UPPER JET/FRONTAL WAVES SUPPORT WILL ACT TO INCREASE AND FOCUS
MOISTURE AND INSTABILITY RETURN AS EJECTING IMPULSES RIDE/LIFT ON
THE WESTERN PERIPHERY OF A SLOW TO DISLODGE EASTERN U.S. RIDGE.
EXPECT WIDESPREAD ACTIVITY TO ALSO SPREAD TO THE MIDWEST/GREAT
LAKES AND THE SOUTHEAST/EAST THROUGH LATER WEEK, WITH SNOW/ICE
POTENTIAL ON THE NORTH SIDE OF THE PRECIPITATION SHIELD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODELS AND ENSEMBLES CONTINUE TO SHOW FAIRLY GOOD AGREEMENT
FOR THIS REGULAR WORKWEEK ON THE LARGE SCALE PATTERN AND OFFER
SIMILAR WEATHER HAZARD POTENTIAL, BUT DO SHOW SOME VARIABILITY IN
THE LOCAL DETAILS, WHICH MAY TAKE UNTIL THE SHORT RANGE TO FULLY
RESOLVE. REGARDLESS, THERE IS EXCELLENT AGREEMENT THAT AN
IMPACTFUL AND MULTI-DAY RAINFALL EVENT SHOULD UNFOLD ACROSS THE
SOUTH, BUT WITH SOME LINGERING UNCERTAINTY ON EXACT LOCATIONS OF
THE HIGHEST RAINFALL AMOUNTS. A GENERAL GUIDANCE BLEND SEEMED TO
PROVIDE A GOOD FORECAST BASIS WEDNESDAY INTO FRIDAY.
BY LATER FRIDAY AND NEXT WEEKEND, GREATER DIFFERENCES ARISE
REGARDING SHORTWAVE ENERGY INTO THE WEST WHICH MAY FINALLY KICK
THE MAIN TROUGH EASTWARD AS STRONG UPPER RIDGING THEN BUILDS
THROUGH THE WEST COAST. RECENT GFS AND TO A LESSER EXTEND GEFS
RUNS HAVE BEEN FASTEST TO PROGRESS THIS ENERGY DOWNSTREAM THROUGH
THE CENTRAL U.S., WHILE RECENT ECMWF RUNS TENDED TO DIG ENERGIES
MORE DEEPLY TOWARD THE SOUTHWEST, RESULTING IN LONGER MAINTAINENCE
OF THE WESTERN MEAN TROUGH. GIVEN UPSTREAM HIGHER AMPLITUDE
PREFERENCE FROM ALASKA TO THE EASTERN PACIFIC, LEANED TOWARD A
COMPROMISE TO SLOWER EVOLUTION SIDE OF THE FULL ENVELOPE OF
SOLUTIONS FOR THE CONUS, PROBABLY OVERALL CLOSEST TO THE ECMWF
ENSEMBLE MEAN. THE LATEST 00 UTC MODEL CYCLE SHOWS THE GFS
TRENDING SLOWER AND THE ECMWF TRENDING FASTER, NOW BOTH BETTER IN
LINE WITH THE ECMWF ENSEMBLE MEAN.
..WEATHER/HAZARDS HIGHLIGHTS
THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA WILL SEE PERIODS OF
MODERATE RAINS INTO MID-LATER WEEK WITH MULTIPLE PACIFIC SYSTEM
APPROACHES. DIGGING ENERGIES INTO A MEAN UPPER TROUGH OVER THE
WEST IN THIS PERIOD SHOULD ALLOW FOR PRECIPITATION TO WORK INLAND
TO THE NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES TO INCLUDE SOME
ENHANCED TERRAIN/MOUNTAIN SNOWS. UPPER RIDGE BUILDING UP/INLAND
THROUGH THE WEST COAST HEADING INTO THE WEEKEND SHOULD
INCREASINGLY LIMIT ACTIVITY WITH A MORE NORTHWARD TO OFFSHORE
FOCUS.
DOWNSTREAM, INCREASING MOISTURE AHEAD OF THE WESTERN U.S. UPPER
TROUGHING WILL INCREASINGLY SPREAD RAIN INTO THE SOUTH-CENTRAL
U.S. EARLY WEEK. HEAVIEST RAIN TOTALS REMAIN FORECAST TO SLOWLY
SPREAD THROUGH TEXAS TO THE LOWER MISSISSIPPI/TENNESSEE VALLEYS
AND GULF COAST STATES AND SOUTHEAST INTO MID/LATER WEEK, AND THESE
WILL FUEL GROWING FLOODING CONCERNS GIVEN SIGNIFICANT
REPEAT/TRAINING POTENTIAL. WPC DAY 4/WEDNESDAY AND DAY 5/THURSDAY
EXCESSIVE RAINFALL OUTLOOKS HAVE SLIGHT RISK AND SURROUNDING
MARGINAL RISK AREAS FROM SOUTHEAST TEXAS TO THE LOWER
MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES GIVEN SLOW
PATTERN TRANSLATION WITH FAVORABLE UPPER SUPPORT AND DEEP MOISTURE
RETURN AND REPEAT ACTIVITY SIGNATURE.
PRECIPITATION WILL ALSO START SPREADING MORE EARNESTLY ACROSS THE
MIDWEST/GREAT LAKES AND THE EAST INTO MID-LATER WEEK AFTER A DRY
PERIOD, AND GIVEN MUCH WARMER TEMPERATURES AND SNOWMELT, AREAL AND
STREAM FLOODING MAY BECOME A CONCERN. THERE IS ALSO QUITE A BIT OF
UNCERTAINTY WITH LATER WEEK INDIVIUAL LIFTING FRONTAL WAVES WITHIN
THE LARGER SCALE FLOW AND THE EXTENT AND FOCUS OF POTENTIAL
COASTAL WAVES NEXT WEEKEND TO MONITOR. MEANWHILE, THERE REMAINS
SOME PROBABILITIES FOR FREEZING RAIN ACROSS PARTS OF THE
MIDWEST/GREAT LAKES INTO MID-LATER WEEK. WINTRY PRECIP SHOULD
TRANSITION TO RAIN AS WARM AIR SPREADS FARTHER NORTH. LINGERING
COOLED AIR FROM THE GREAT LAKES/APPALACHIANS TO THE NORTHERN
NORTHEAST SEEM MOST LIKELY TO SEE WINTRY WEATHER LATER WEEK AND
INTO THE NEXT WEEKEND WITH ADDITIONAL BUT STILL UNCERTAIN
FRONTAL/COASTAL WAVES.
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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