614
FXUS02 KWBC 300700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST FRI DEC 30 2022
VALID 12Z MON JAN 02 2023 - 12Z FRI JAN 06 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 EARLY THROUGH MIDWEEK...
...MORE ROUNDS OF MODERATE TO HEAVY PRECIPITATION FOR THE WEST
WITH FOCUS ACROSS CALIFORNIA NEXT WEEK...
..OVERVIEW
A DEEPENED LOW PRESSURE SYSTEM FORECAST TO DEVELOP INTO EARLY NEXT
WEEK OVER THE CENTRAL U.S. WILL LIKELY LEAD TO A WINTER WEATHER
EVENT FROM THE NORTH-CENTRAL ROCKIES/PLAINS THROUGH THE UPPER
MIDWEST, WHILE HEAVY RAIN AND SEVERE WEATHER APPEAR LIKELY ACROSS
THE SOUTH MONDAY-WEDNESDAY. MEANWHILE THE WEST SHOULD SEE
ADDITIONAL ROUNDS OF MODERATE TO HEAVY PRECIPITATION NEXT WEEK,
WITH HIGHEST AMOUNTS MAINLY ACROSS CALIFORNIA NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES AGAIN OFFER A SIMILAR MID-LARGER SCALE
PATTERN EVOLUTION, ALBEIT WITH AMPLE EMBEDDED SYSTEM DIFFERENCES
BY TUESDAY TO SHIFT MAIN LOCAL WEATHER FOCUS. THAT SAID, THERE
SEEMS TO BE REASONABLY GOOD PREDICTABILITY WITH THE DEPICTION OF
THE MAIN HIGHLIGHTED THREATS TO MONITOR INTO SHORT RANGE TIME
FRAMES. THE MOST EVIDENT VARIANCES BETWEEN GUIDANCE AND WITH RUN
TO RUN CONTINUITY CONCERNS SEEM TO REMAINS WHERE THE COMMAHEAD
HEAVY SNOW/ICE AXIS WILL SETUP ACROSS THE NORTH-CENTRAL STATES
EARLY NEXT WEEK WITH UNCERTAIN MAIN LOW TRACK/STREAM PHASING, LEAD
LOW/FRONTAL DEPECTIONS AND ALSO THE TIMING AND FOCUS WITH A SERIES
OF PACIFIC SYSTEMS TO WORK INTO AN UNSETTLED WEST IN ACTIVE FLOW.
COMPARED TO MOST RECENT GUIDANCE, THE LATEST FEW RUNS OF THE ECMWF
AND TO A LESSER EXTENT ECMWF ENSEMBLES REMAIN FARTHER TO THE SOUTH
WITH DEVELOPMENT AND TRACK OF A DEEPENING CENTRAL U.S. LOW EARLY
NEXT WEEK AND ALSO MORE PROGRESSIVE AND WETTER WITH UPCOMING BOUTS
OF PRECIPITATION NEXT WEEK INTO THE WEST. WPC CONTINUITY HAS BEEN
LEANING 2/3 OF THE WAY TOWARD THE MORE NORTHERN TRACK OF THE
CENTRAL U.S. MAIN LOW WITH ASSOCIATED DOWNSTREAM FLOW DEPICTIONS
AS WELL AS NEAR COMPOSITE FOR WESTERN U.S. SYSTEM TIMINGS, BUT
SOMEWHAT ON THE WET SIDE GIVEN REASONABLE SUPPORT.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY
DERIVED FROM A COMPOSITE GFS/ECMWF/UKMET/CANADIAN MODEL BLEND
VALID MONDAY BEFORE TRANSITIONING STARTING TUESDAY INSTEAD TO A
COMPOSITE BLEND OF MORE COMPATIBLE GUIDANCE FROM THE GEFS/ECMWF
ENSEMBLE MEANS AND THE NATIONAL BLEND OF MODELS (NBM). THIS
SOLUTION TENDS TO MITIGATE THE EMBEDDED SYSTEM DIFFERENCES
CONSISTENT WITH UNCERTAINTY AND ALSO ACTS TO MAINTAIN GOOD WPC
PRODUCT CONTINUITY. NATIONAL BLEND QPF WAS IN GENERAL ADJUSTED
PARTIALLY TOWARD WPC CONTINUITY TO PROVIDE THE MOST STABLE RUN TO
RUN DEPCITIONS.
..WEATHER/HAZARD HIGHLIGHTS
UPPER TROUGH EMERGENCE WILL SUPPORT HEAVY SNOW ACROSS THE CENTRAL
ROCKIES THIS WEEKEND INTO MONDAY. SUBSEQUENT SURFACE LOW PRESSURE
CONSOLIDATION ACROSS THE CENTRAL HIGH PLAINS WILL THEN BRING A
SWATH OF SNOW ACROSS THE NORTHERN HALF OF THE PLAINS INTO THE
UPPER MIDWEST, ALONG WITH INCREASINGLY WINDY CONDITIONS AND AN ICY
TRANSITIONAL ZONE. INFLOW EAST OF THE LOW AND LINGERING COLD AIR
MAY ALSO SUPPORT SOME LATER PERIOD SNOW/ICE DOWNSTREAM FROM THE
NORTHERN GREAT LAKES TO A COOLED NORTHEAST. 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 LOWER MISSISSIPPI VALLEY/MID-SOUTH THROUGH THE
SOUTHEAST MONDAY-WEDNESDAY. THEREAFTER, A TRAILING FRONTAL LOW
PRESSURE SYSTEM COULD DEVELOP UNDER THE RIGHT ENTRANCE REGION
UPPER JET AND THEN LIFT OVER THE EAST. THIS COULD SPREAD SOME
MODERATE TO HEAVY RAIN UP THE MID-ATLANTIC STATES AND COASTAL NEW
ENGLAND.
WPC EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK (ERO) "SLIGHT" RISK
AREAS HAVE BEEN ISSUED FOR MONDAY AND TUESDAY ACROSS THE SOUTH.
THE WEST COAST STATES CAN EXPECT A BRIEF BREAK FROM THE HEAVY
PRECIPITATION ON SUNDAY AS THE TROUGH AXIS SHIFTS FARTHER TO THE
EAST. BUT ADDITIONAL ROUNDS OF PRECIPITATION ARE EXPECTED AS THE
WEEK PROGRESSES. THERE IS QUITE A BIT OF 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 FROM THE
PACIFIC. MANY AREAS ARE LIKELY TO BE SENSITIVE TO ADDITIONAL
RAINFALL BY THEN 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. AS THE LARGE-SCALE UPPER TROUGH MOVES THROUGH
THE WESTERN U.S. INTO THE PLAINS, NEAR TO BELOW AVERAGE
TEMPERATURES ARE EXPECTED TO WORK THEIR WAY FROM WEST TO EAST
ACROSS THESE AREAS.
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, 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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