722
FXUS02 KWBC 101902
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EST TUE JAN 10 2023
VALID 12Z FRI JAN 13 2023 - 12Z TUE JAN 17 2023
...UNSETTLED AND ACTIVE PATTERN CONTINUES FOR WESTERN U.S. WITH
FOCUS ON CALIFORNIA ATMOSPHERIC RIVERS...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE PARADE OF UPPER LEVEL TROUGHS ENTERING THE WEST COAST WILL
CONTINUE INTO THE MEDIUM RANGE PERIOD. THE LATEST GUIDANCE HAS
TRENDED FASTER THAN PREVIOUS CYCLES WITH THE BROAD SCALE FLOW OF
SYSTEMS ACROSS THE CONUS. A DETERMINISTIC GENERAL MODEL BLEND
CONSISTING OF THE 00Z SUITE OF EC/CMC/UK MODELS AND THE 06Z GFS
WAS USED TO CAPTURE THE DEPARTURE OF AN EAST COAST SYSTEM AND THE
ARRIVAL OF A PAIR OF UPPER TROUGHS IN THE WEST ON DAYS 4 AND 5 NOT
TO MENTION THE AMPLIFICATION OF A CENTRAL CONUS RIDGE. THE 06Z GFS
AND 00Z CMC WERE MORE PROGRESSIVE AND PREFERRED TO THE 00Z EC
REGARDING THE DEPARTING EAST COAST SYSTEM. THIS IS REFLECTED BY
LOWER TOTALS IN OUR OFFICIAL QPF. 06Z GEFS AND THE 00Z ECE WERE
INTRODUCED TO THE BLEND ON DAY 5 TO MODERATE SOME OF THE DEEP
AMPLIFICATION TAKING PLACE IN THE DETERMINISTIC GUIDANCE. THE 00Z
CMCE WAS INTRODUCED BY DAY 6 AND THE GFS PHASED OUT BY DAY 7 WHEN
THE BLEND CONSISTED OF PREDOMINANTLY ENSEMBLE MEANS.
..WEATHER/HAZARD HIGHLIGHTS
UNSETTLED AND ACTIVE WEATHER IS EXPECTED TO CONTINUE ACROSS
PORTIONS OF THE WEST AS A SERIES OF ATMOSPHERIC RIVERS MOVE
ONSHORE. THE HIGHLY AMPLIFIED PATTERN MENTIONED ABOVE WILL HELP
FOCUS THE BEST MOISTURE TRANSPORT AND RAINFALL ALONG THE IMMEDIATE
NORTHWEST CALIFORNIA COAST INTO FRIDAY, AND FURTHER UP THE PACIFIC
NORTHWEST COAST AFFECTING COASTAL REGIONS OF OREGON AND
WASHINGTON. HOWEVER, BY THIS WEEKEND, ANOTHER STRONG WEATHER
SYSTEM APPROACHES CENTRAL CALIFORNIA AND WILL BRING ANOTHER ROUND
OF WIDESPREAD PRECIPITATION. THIS SYSTEM WILL IMPACT A LARGER AREA
OF CALIFORNIA WITH EVEN MORE HEAVY RAINFALL THREATS. WORSENING
FLOODING OR DELAYED IMPROVEMENT OF ONGOING ISSUES IS POSSIBLE
AGAIN ACROSS A VERY OVER-SATURATED COASTAL CENTRAL TO SOUTHERN
CALIFORNIA WHILE THE HIGHER ELEVATIONS OF THE SIERRA SEE HEAVY
SNOWFALL. AS THE ENERGY MOVES INLAND ON SUNDAY, RAIN AND HIGHER
ELEVATION SNOWS ARE POSSIBLE IN THE SOUTHWEST, AND EVENTUALLY
RETURN FLOW OUT OF THE GULF OF MEXICO MAY INCREASE PRECIPITATION
CHANCES INTO THE PLAINS/LOWER MISSISSIPPI VALLEY AS WELL.
MEANWHILE, BACK TO THE EAST, MOST OF THE PRECIPITATION WILL LIKELY
HAVE EXITED THE EAST COAST BY EARLY FRIDAY, EXCEPT FOR SOME
LINGERING, AND LOCALLY HEAVY, RAINFALL ALONG THE NEW ENGLAND
COAST. ANY SNOWFALL WITH THIS SYSTEM LIKELY REMAINS CONFINED TO
HIGHER ELEVATIONS AND LOCATIONS WELL INLAND. AS A SECONDARY LOW
PRESSURE AREA DEVELOPS OFF THE NORTHEAST COAST, THERE IS SOME
POTENTIAL FOR WRAP BACK SNOWS ACROSS PARTS OF THE NORTHEAST INTO
SATURDAY, BUT THIS EVOLUTION AND THREAT IS HIGHLY UNCERTAIN AND
DEPENDENT ON EXACT PROXIMITY OF THE LOW TO THE COAST.
PARTS OF THE NORTHEAST COULD BE WELL ABOVE NORMAL TO START ON
FRIDAY, BUT SHOULD TREND BACK TO NORMAL THIS WEEKEND. GENERALLY
WARMER THAN NORMAL TEMPERATURES ARE EXPECTED ACROSS THE CENTRAL
U.S. THROUGH THE PERIOD, PARTICULARLY BY LATER THIS WEEKEND INTO
EARLY NEXT WEEK WHERE PARTS OF THE PLAINS AND INTO THE MIDWEST
COULD SEE HIGH TEMPERATURES 15 TO 20 DEGREES F ABOVE NORMAL. EVEN
MORE IMPRESSIVE WILL BE THE VERY WARM NIGHTTIME LOWS, WITH
READINGS 20 TO 25 DEGREES F ABOVE NORMAL ACROSS THE MISSISSIPPI
VALLEY AND INTO THE MIDWEST MONDAY-TUESDAY.
KEBEDE/SANTORELLI
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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