577
FXUS02 KWBC 200658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST SAT JAN 20 2024
VALID 12Z TUE JAN 23 2024 - 12Z SAT JAN 27 2024
...MULTI-DAY EXCESSIVE RAINFALL AND FLOODING THREATS FOR THE LOWER
MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES NEXT WEEK...
..OVERVIEW
MODELS AND ENSEMBLES AGREE THAT THE LARGE SCALE PATTERN ALOFT NEXT
WEEK WILL SHIFT NOTABLY FROM THIS WEEK'S FRIGID PATTERN, AS A
RIDGE SHIFTS FROM THE CENTRAL U.S. INTO THE EAST AND TROUGHING
BECOMES ESTABLISHED IN THE WESTERN TO 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
PRECIPITATION FOCUSING SHORTWAVES WILL WORK INLAND INTO THE
PACIFIC NORTHWEST AND DIG INTO THE WESTERN U.S. TROUGH NEXT WEEK
IN UNSETTLED/COOLED FLOW, THEN PROPAGATE DOWNSTREAM TO RIDE THE
WESTERN PERIPHERY OF THE DOWNSTREAM UPPER RIDGE. A SIGNIFICANT
RAINFALL EVENT IS LOOMING AS MULTIPLE DAYS OF HEAVY RAIN AND
RUNOFF THREATS ARE EXPECTED AMID THE STALLING UPPER FLOW MEAN
PATTERN, WITH PRIMARY FOCUS OVER THE LOWER MISSISSIPPI/TENNESSEE
VALLEYS AND GULF COAST STATES. EJECTING SHORTWAVES AND FAVORABLE
UPPER JET/FRONTAL WAVES SUPPORT WILL ACT TO INCREASE AND FOCUS
MOISTURE AND INSTABILITY RETURN ON THE WESTERN PERIPHERY OF A SLOW
TO DISLODGE EASTERN U.S. SURFACE RIDGE. EXPECT WIDESPREAD ACTIVITY
TO ALSO SPREAD TO THE MIDWEST/GREAT LAKES AND THE SOUTHEAST/EAST
THROUGH MID-LATER NEXT WEEK, WITH SNOW/ICE POTENTIAL ON THE NORTH
SIDE OF THE PRECIPITATION SHIELD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
12/18/00 UTC GUIDANCE CYCLE SOLUTIONS FOR BOTH THE OVERALL PATTERN
EVOLUTION/SCOPE AND SENSIBLE WEATHER THREAT FOCI SEEM REASONABLY
WELL CLUSTERED THROUGH MUCH OF NEXT WEEK AND REMAIN RUN TO RUN
CONSISTENT, BOLSTERING FORECAST CONFIDENCE. LOCAL DETAIL AND FOCUS
ALWAYS OFFER MORE CHALLENGE, BUT A COMPOSITE OF THE
GFS/ECMWF/UKMET/CANADIAN AND GEFS/ECMWF ENSEMBLE MEANS ALONG WITH
THE NBM PROVIDES A SOLID FORECAST BASIS WITH SIMILAR THREAT FOCUS
SIGNALS TO EVALUATE NEEDED ACTION THAT SEEMS CONSISTENT WITH A
PATTERN WITH ABOVE NORMAL PREDICTABILITY. THIS APPROACH MAINTAINS
A VERY CONSISTENT FORECAST WITH THE PREVIOUS SEVERAL WPC SHIFTS.
..WEATHER/HAZARDS HIGHLIGHTS
PORTIONS OF THE WEST CAN EXPECT SEVERAL PERIODS OF ENHANCED
PRECIPITATION NEXT WEEK. AN EARLY WEEK ATMOSPHERIC RIVER SINKING
SOUTHWARD THROUGH CALIFORNIA WILL WANE, BUT LINGERING MOISTURE AND
EMERGING AND FAVORABLE UPPER TROUGH/JET SUPPORT MAY ALLOW FOR SOME
LOCAL DOWNPOURS/RUNOFF ISSUES FROM SOUTHERN ARIZONA TO SOUTHWEST
NEW MEXICO. A WPC ERO MARGINAL RISK AREA IS IN PLACE FOR THE DAY
4/TUESDAY. MEANWHILE, THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA
AND VICINITY WILL SEE MULTIPLE PERIODS OF PRECIPITATION NEXT WEEK,
SEEMINGLY WITH MORE EMPHASIS INTO MID-LATER NEXT WEEK WITH
STRONGER PACIFIC SYSTEM APPROACHES. EXPECT MAINLY MODERATE DAILY
TOTALS.
DOWNSTREAM, DEEPLY INCREASING MOISTURE AHEAD OF THE WESTERN U.S.
UPPER TROUGHING WILL INCREASINGLY SPREAD RAIN INTO THE
SOUTH-CENTRAL U.S. EARLY NEXT WEEK. HEAVIEST RAIN TOTALS ARE
FORECAST TO SLOWLY SPREAD THROUGH THE LOWER MISSISSIPPI/TENNESSEE
VALLEYS AND GULF COAST STATES AND SOUTHEAST BY MID/LATER NEXT
WEEK, AND THESE WILL FUEL GROWING FLOODING CONCERNS GIVEN
SIGNIFICANT REPEAT/TRAINING POTENTIAL. WPC DAY 4/TUESDAY AND DAY
5/WEDNESDAY EXCESSIVE RAINFALL OUTLOOKS SLIGHT RISK AREAS AND
SURROUNDING MARGINAL RISK AREAS ARE SLUGGISHLY MOVE FROM FROM
SOUTHEAST TEXAS THROUGH THE LOWER MISSISSIPPI VALLEY THEN
TENNESSEE VALLEY GIVEN SLOW PATTERN TRANSLATION AND OVERALL
FAVORABLE UPPER JET/FLOW SUPPORT AND SUSTAINED MOISTURE RETURN AND
REPEAT ACTIVITY SIGNATURE.
PRECIPITATION WILL ALSO START SPREADING MORE EARNESTLY ACROSS THE
MIDWEST/GREAT LAKES AND THE EAST INTO MID-LATER NEXT WEEK AFTER A
DRY PERIOD, AND GIVEN MUCH WARMER TEMPERATURES AND SNOWMELT, AREAL
AND STREAM FLOODING MAY BECOME A CONCERN. THERE ARE SOME
PROBABILITIES FOR FREEZING RAIN ACROSS PARTS OF THE MIDWEST.
WINTRY PRECIP SHOULD THEN TRANSITION TO RAIN AS WARM AIR SPREADS
FARTHER NORTH. THE GREAT LAKES/APPALACHIANS TO THE INTERIOR
NORTHEAST SEEM MOST LIKELY TO ALSO EXPERIENCE WINTRY WEATHER WITH
OVERALL SYSTEM AND PATTERN EVOLUTION LATER NEXT WEEK WITH THE LAST
VESTIGES OF THE AMBIENT COLD AIRMASS.
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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