096
FXUS02 KWBC 291901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST THU DEC 29 2022
VALID 12Z SUN JAN 01 2023 - 12Z THU JAN 05 2023
...WINTER STORM THREAT FOR THE NORTH-CENTRAL ROCKIES/PLAINS AND
UPPER MIDWEST EARLY NEXT WEEK AS A HEAVY RAIN/SEVERE WEATHER
THREAT REEMERGES FOR THE MID-LOWER MISSISSIPPI VALLEY/MID-SOUTH
THEN SOUTHEAST MIDWEEK...
...MORE ROUNDS OF MODERATE TO HEAVY PRECIPITATION FOR THE WEST
WITH FOCUS ACROSS CALIFORNIA THROUGH MIDWEEK...
..OVERVIEW
A LOW PRESSURE SYSTEM FORECAST TO DEVELOP EARLY NEXT WEEK OVER THE
CENTRAL U.S. WILL LIKELY LEAD TO A WINTER WEATHER EVENT FROM THE
NORTH-CENTRAL ROCKIES THROUGH THE NORTHERN PLAINS, WHILE HEAVY
RAIN AND SEVERE WEATHER APPEAR LIKELY ACROSS THE DEEP SOUTH TO
THE SOUTHEAST MONDAY-WEDNESDAY AHEAD OF A COLD FRONT. MEANWHILE,
THE WEST SHOULD SEE ADDITIONAL ROUNDS OF MODERATE TO HEAVY
PRECIPITATION NEXT WEEK, WITH HIGHEST AMOUNTS MAINLY ACROSS
CALIFORNIA THROUGH MIDWEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO INDICATE THE FORMATION OF THE LOW
PRESSURE SYSTEM OVER THE CENTRAL U.S. EARLY NEXT WEEK. THE ECMWF
HAS CONTINUED TO SHOW A LOW TRACK THAT IS QUITE A BIT FARTHER TO
THE SOUTH TOWARD THE GREAT LAKES THAN THE REST OF THE GUIDANCE.
BY MIDWEEK, THE ECMWF HAS BEEN FASTER BRINGING IN THE NEXT SYSTEM
TOWARD CALIFORNIA. IN THE MEANTIME, THE ECMWF LIKES TO FAVOR THE
DEVELOPMENT OF ANOTHER LOW TRACKING FROM THE DEEP SOUTH TOWARD THE
NORTHERN MID-ATLANTIC THAN THE GFS AND CMC.
THE WPC FORECAST KEEPS A MIDDLE GROUND SOLUTION BY BLENDING 40% OF
THE 06Z GFS/GEFS, 40% OF THE 00Z ECMWF/EC MEAN WITH THE REST OF
THE CONTRIBUTIONS FROM THE 00Z CMC/CMC MEAN AND THE 00Z UKMET,
TRANSITIONING TO MOSTLY A BLEND OF THE ENSEMBLE MEANS BY DAY 7.
..WEATHER/HAZARD HIGHLIGHTS
THE NORTHEASTERN U.S. COULD SEE SOME MAINLY RAIN SHOWERS (WITH
PERHAPS SOME MINOR SNOW ACCUMULATIONS IN HIGHER ELEVATIONS) EARLY
SUNDAY WITH AN EXITING LOW PRESSURE SYSTEM. THEN, AS THE NEXT
UPPER TROUGH EMERGES AFTER PRODUCING POSSIBLY HEAVY SNOW ACROSS
THE CENTRAL ROCKIES, SURFACE LOW PRESSURE CONSOLIDATING ACROSS THE
CENTRAL HIGH PLAINS SHOULD BRING A SWATH OF SNOW ACROSS THE
NORTHERN HALF OF THE HIGH PLAINS INTO THE UPPER MIDWEST, ALONG
WITH INCREASINGLY WINDY CONDITIONS WITH AN ICY TRANSITION ZONE
POSSIBLE. LEAD FLOW AROUND THE LOW AND LINGERING COLD AIR MAY ALSO
SUPPORT SOME SNOW/ICE DOWNSTREAM FROM THE NORTHERN GREAT LAKES TO
NORTHERN NEW ENGLAND. MEANWHILE FARTHER SOUTH, THE FRONTAL SYSTEM
ASSOCIATED WITH THIS LOW AND FAVORABLE GULF MOISTURE/INSTABILITY
AND RIGHT ENTRANCE REGION UPPER JET LIFT SHOULD PROVIDE A FOCUS
FOR ANOTHER EPISODE OF WIDESPREAD HEAVY RAIN, ALONG WITH A THREAT
OF SEVERE WEATHER AS PER SPC, ACROSS PARTS OF THE MISSISSIPPI
VALLEY INTO THE TENNESSEE VALLEY AND SOUTHEAST BY MONDAY-WEDNESDAY.
THE WEST COAST STATES CAN EXPECT A BRIEF BREAK FROM THE HEAVY
PRECIPITATION ON SUNDAY AS THE TROUGH AXIS SHIFTS EAST/FARTHER
INLAND. BUT ADDITIONAL ROUNDS OF PRECIPITATION ARE FORECAST TO
ARISE AS THE WEEK PROGRESSES. THERE IS CONSIDERABLE UNCERTAINTY
WITH THE TIMING OF ADDITIONAL HEAVY PRECIPITATION EVENTS AT THIS
POINT, BUT GENERALLY AMOUNTS LOOK TO TREND UPWARD BY
TUESDAY-THURSDAY ACROSS CALIFORNIA AS A STRONGER FRONTAL SYSTEM
APPROACHES. MANY AREAS ARE LIKELY TO BE SENSITIVE TO ADDITIONAL
RAINFALL BY THAT TIME GIVEN THE AMPLE RECENT RAINFALL AND
ADDITIONAL RAIN DURING THE SHORT RANGE PERIOD.
MILDER THAN AVERAGE TEMPERATURES FOR WINTER WILL BE WIDESPREAD
ACROSS THE EASTERN HALF OF THE COUNTRY FOR EARLY NEXT WEEK. LOWS
OF AROUND 15-30F ABOVE AVERAGE AND HIGHS AROUND 10-20F ABOVE
AVERAGE WILL BE COMMON, EVEN REACHING 20-30F ANOMALIES IN THE OHIO
VALLEY/GREAT LAKES TUESDAY AND THE NORTHEAST ON WEDNESDAY. DAILY
RECORDS FOR WARM LOWS COULD BE WIDESPREAD FOR PARTS OF THE CENTRAL
AND EASTERN U.S., WHILE DAILY RECORD HIGHS ARE POSSIBLE AS WELL
ESPECIALLY IN THE OHIO VALLEY. MEANWHILE IN THE WEST, THE OVERALL
WET/SNOWY PATTERN WILL TEND TO KEEP DAYTIME TEMPERATURES AROUND
5-10F BELOW NORMAL. LOWS SHOULD GENERALLY BE A BIT ABOVE AVERAGE
SUNDAY MORNING BEFORE THE SECOND LARGE-SCALE UPPER TROUGH MOVES
THROUGH, BRINGING LOWS WITHIN A FEW DEGREES OF NORMAL. THIS TROUGH
AND THE ASSOCIATED COLD FRONT WILL BRING THE PLAINS CLOSER TO
AVERAGE BY TUESDAY-WEDNESDAY, TRACKING INTO THE EAST-CENTRAL U.S.
BY THURSDAY.
KONG/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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