490
FXUS02 KWBC 011903
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SUN JAN 01 2023
VALID 12Z WED JAN 04 2023 - 12Z SUN JAN 08 2023
...MORE HEAVY PRECIPITATION EXPECTED TO REACH THE WEST COAST WITH
THE MOST SIGNIFICANT EPISODE WED-THU IN CALIFORNIA...
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES ARE NOW UNANIMOUS IN BRINGING A RATHER DEEP
CYCLONE CLOSER TOWARD BUT OFF THE PACIFIC NORTHWEST COAST ON
THURSDAY, WITH THE CMC HAVING A STORM TRACK CLOSEST TO THE COAST.
THE BULK OF THE MOISTURE AHEAD OF THE CYCLONE IS FORECAST TO BE
PRECIPITATED OVER CALIFORNIA STARTING ON WEDNESDAY, CULMINATING ON
THURSDAY. GUIDANCE HAS BEEN VERY CONSISTENT IN THIS REGARD.
MEANWHILE IN THE EASTERN U.S., MODELS HAVE BEEN SLOWLY PUSHING THE
COLD FRONT FASTER TOWARD THE EAST COAST, LEADING TO A LOWERING
THREAT OF HEAVY RAIN ACROSS THE SOUTHEAST THAN IN PREVIOUS
FORECASTS ON WEDNESDAY. ACROSS THE NORTHEAST, MODELS ARE SLOWLY
CONVERGING MIDWAY BETWEEN THE SLOWER ECMWF SOLUTION AND THE FASTER
GFS SOLUTION IN DEPICTING A SHEARED LOW PRESSURE WAVE SLIDING OFF
THE NEW ENGLAND COAST WITH LINGERING SURFACE TROUGHING EXTENDING
WEST INTO THE GREAT LAKES AS COLDER AIR ARRIVES FROM EASTERN
CANADA ON THURSDAY. A LINGERING UPPER WAVE/LOW MAY INTERACT WITH
THE SURFACE TROUGH AND THE COLD AIR TO DELIVER A PERIOD OF SNOW OR
MIXED PRECIPITATION ACROSS THE INTERIOR NORTHEAST INTO FRIDAY. BY
NEXT WEEKEND, A COUPLE OF PACIFIC FRONTAL SYSTEMS ARE FORECAST TO
BRING THE NEXT SURGE OF MOISTURE INTO THE WEST COAST WITH
UNCERTAIN SYSTEM TIMINGS. MEANWHILE, LINGERING UPPER-LEVEL
TROUGHING MOVING THROUGH THE INTERMOUNTAIN WEST IS FORECAST TO
REACH THE CENTRAL PLAINS NEXT WEEKEND AND WOULD HELP DEVELOP A
RELATIVELY WEAK FRONTAL WAVE THAT IS FORECAST TO TRACK GENERALLY
TOWARD THE GREAT LAKES.
GIVEN BETTER MODEL AGREEMENT IN THE MEDIUM RANGE TIME SCALES, A
COMPOSITE BLEND OF THE 06Z GFS, 00Z ECMWF, WITH SOME CONTRIBUTIONS
FROM THE 00Z CANADIAN MODEL SEEMS TO OFFER A REASONABLE FORECAST
STARTING POINT FOR THE MEDIUM-RANGE FORECASTS TODAY. INCREASED
INCORPORATION OF THE ENSEMBLE MEANS APPEARS COMPATIBLE WITH
FORECAST CONTINUITY INTO NEXT WEEKEND.
..WEATHER/HAZARD HIGHLIGHTS
THERE IS SOME CHANCE FOR SNOW IN MARGINALLY COOLED AIR FROM THE
LOWER GREAT LAKES THROUGH THE NORTHERN NORTHEAST THROUGH MIDWEEK
WITH SYSTEM PASSAGE. MEANWHILE TO THE SOUTH, A WAVY FRONTAL SYSTEM
WILL DEVELOP AND SPREAD SOME MODERATE RAIN UP THE EASTERN SEABOARD
MIDWEEK, WITH UNCERTAIN ADDITIONAL/MODEST FRONTAL WAVE FORMATION
OFFSHORE POSSIBLY LINGERING SOME LIGHT QPF INTO THE
MID-ATLANTIC/COASTAL NORTHEAST INTO LATER NEXT WEEK. PRIOR TO
THIS, MUCH MILDER THAN AVERAGE TEMPERATURES WILL LINGER ACROSS
MUCH OF THE EASTERN SEABOARD INTO MIDWEEK. TEMPERATURES OF AROUND
15-30F ABOVE AVERAGE WILL BE COMMON WITH WIDESPREAD RECORD WARM
MORNING LOWS FORECAST FOR WEDNESDAY.
IT REMAINS THE EXPECTATION THAT ADDITIONAL ROUNDS OF PRECIPITATION
ARE ALSO EXPECTED TO REACH THE WEST COAST THIS WEEK IN A VERY WET
AND ACTIVE PATTERN IN THE PACIFIC TO START 2023, BUT STILL WITH A
FOCUS PRIMARILY ON CALIFORNIA. THIS LATEST EPISODE OF HEAVIEST
PRECIPITATION IS EXPECTED TO CULMINATE WEDNESDAY-THURSDAY AS A
SYSTEM APPROACHES FROM THE PACIFIC WITH ANOTHER POTENTIAL
ATMOSPHERIC RIVER EVENT TO SHIFT STEADILY SOUTHWARD ACROSS THE
STATE OVER TIME. MANY AREAS ARE LIKELY TO BE SENSITIVE TO
ADDITIONAL RAINFALL BY THEN GIVEN THE AMPLE RECENT RAINFALL IN
ADDITION TO THE RAIN EXPECTED DURING THE SHORT RANGE PERIOD. THIS
WILL BE FOLLOWED BY AN ADDITIONAL CHANCE FOR AN UPTICK IN
PRECIPITATION WITH ADDITIONAL SYSTEM APPROACH LATTER WEEK. WPC
EXPERIMENTAL MEDIUM RANGE EXCESSIVE RAINFALL OUTLOOK (ERO)
"SLIGHT" RISK AREAS HAVE BEEN ISSUED FOR THE WEDNESDAY-THURSDAY
EPISODE. THERE IS ALSO A MULTI-DAY THREAT FOR HEAVY SNOW THAT WILL
FOCUS ALONG THE SIERRA THIS WEEK, BUT ALSO SPREAD NORTHWARD
THROUGH THE CASCADES AND WITH SOME GUSTO INLAND ACROSS THE
INTERMOUNTAIN WEST TOWARD THE ROCKIES OVER TIME WITH SYSTEM
TRANSLATION. THIS THREAT IS ADDRESSED IN THE WPC WINTER WEATHER
OUTLOOK (WWO) AND OTHER PRODUCTS. SYSTEM/ENERGY TRANSLATION AND
ASSOCIATED/MODEST SURFACE SYSTEM GENESIS IS THEN EXPECTED TO WORK
DOWNSTREAM ACROSS THE CENTRAL TO EAST CENTRAL U.S. HEADING INTO
NEXT WEEKEND, BUT WITH LIMITED QPF POTENTIAL.
KONG/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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