581
FXUS02 KWBC 070649
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EST SAT JAN 07 2023
VALID 12Z TUE JAN 10 2023 - 12Z SAT JAN 14 2023
...ADDITIONAL ATMOSPHERIC RIVERS EVENTS WITH HEAVY RAIN AND
MOUNTAIN SNOW FOR MUCH OF CALIFORNIA NEXT WEEK WITH FLOODING
EXPECTED...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE WEATHER PATTERN OVER MUCH OF THE CONTINENTAL U.S. SHOULD
REMAIN QUITE ACTIVE THROUGH NEXT WEEK, WITH MULTIPLE EMBEDDED
SHORTWAVES CROSSING THE WEST COAST AND MOVING EASTWARD THROUGH THE
SOUTH-CENTRAL U.S. AND EVENTUALLY THE EAST. THERE IS VERY GOOD
AGREEMENT IN THE GUIDANCE THAT THE PATTERN SHOULD TREND MORE
AMPLIFIED WITH TIME AS UPPER RIDGING BUILDS OVER THE CENTRAL U.S.
SANDWICHED BETWEEN AMPLIFIED TROUGHS ALONG BOTH THE WEST AND EAST
COASTS. THE HIGHLIGHT THIS FORECAST PERIOD CONTINUES TO BE A VERY
ACTIVE EASTERN PACIFIC SENDING MULTIPLE SHORTWAVES/ATMOSPHERIC
RIVERS INTO CALIFORNIA WHICH WILL ONLY EXACERBATE ONGOING FLOODING
CONCERNS IN THAT REGION. THERE IS MODERATE TO HIGH CONFIDENCE IN
THE OVERALL SYNOPTIC PATTERN, BUT LOW CONFIDENCE IN THE DETAILS OF
INDIVIDUAL SHORTWAVES. THE FIRST SHORTWAVE THROUGH THE WEST
TUESDAY-WEDNESDAY SHOWS SOME MINOR TIMING DIFFERENCES, BUT THIS
FEATURE BECOMES MORE UNCERTAIN AS IT CLOSES OFF AN UPPER LOW OVER
THE CENTRAL PLAINS AROUND THURSDAY WITH SURFACE CYCLOGENESIS
LIKELY ACROSS THE SOUTH-CENTRAL U.S. DETAILS ARE IMPORTANT FOR
SNOW/ICE POTENTIAL ON THE NORTH SIDE OF THIS SYSTEM BUT ESPECIALLY
ACROSS PARTS OF THE NORTHEAST AS THERE IS SUPPORT FOR A POSSIBLE
NOR'EASTER LATE NEXT WEEK INTO THE WEEKEND. AGAIN, CONFIDENCE IS
VERY LOW ON ANY SORT OF SIGNIFICANT SYSTEM BUT ITS WORTH KEEPING
AN EYE ON THE UPCOMING MODEL TRENDS. THE WPC FORECAST USED A
GENERAL DETERMINISTIC MODEL BLEND FOR DAYS 3-5 WHEN MODEL
AGREEMENT WAS BETTER. BY 6 AND 7, INCORPORATED MORE OF THE
ENSEMBLE MEANS TO HELP SMOOTH OUT THE LATE PERIOD DETAIL
DIFFERENCES (BOTH IN THE EAST AND THE WEST WITH THE NEXT TROUGH
TOWARDS THE COAST). DID CONTINUE TO INCLUDE MODEST AMOUNTS OF THE
DETERMINISTIC GUIDANCE (GFS, ECMWF, AND CMC) FOR SOME ADDED SYSTEM
DEFINITION.
..WEATHER/HAZARD HIGHLIGHTS
THE BIG WEATHER STORY THROUGH NEXT WEEK WILL REMAIN OUT WEST AS
YET MORE ATMOSPHERIC RIVERS TAKE AIM AT AN ALREADY OVER SATURATED
CALIFORNIA. ONE EVENT WILL BE ONGOING AS THE PERIOD BEGINS
TUESDAY, ALTHOUGH THE WORST OF IT ON MONDAY HAS NOW MOVED INTO THE
SHORT RANGE. EVEN STILL, THE WPC EXPERIMENTAL DAY 4 EXCESSIVE
RAINFALL OUTLOOK (ERO) CONTINUES TO HIGHLIGHT A SLIGHT RISK ALONG
THE TRANSVERSE RANGES IN SOUTHERN CALIFORNIA, WHERE RAINFALL
AMOUNTS OF SEVERAL INCHES ARE POSSIBLE. LINGERING RAINS ARE LIKELY
ACROSS CENTRAL TO NORTHERN CALIFORNIA TOO, LOCALLY HEAVY IN SPOTS,
WHERE MANY AREAS ARE ALREADY VERY SENSITIVE TO ADDITIONAL RAINFALL
GIVEN THE RECENT SERIES OF ATMOSPHERIC RIVERS. SIGNIFICANT SNOWS
WILL CONTINUE ACROSS THE SIERRAS INTO TUESDAY WITH SNOW EXTENDING
INTO THE GREAT BASIN AND ROCKIES TOO AS THE UPPER SYSTEM SHIFTS
INLAND. AFTER THIS, THE NEXT SYSTEM LOOKS TO IMPACT CALIFORNIA
AGAIN BY WEDNESDAY-THURSDAY WITH ADDITIONAL AND POTENTIALLY HEAVY
RAINFALL AND HIGHER ELEVATION SNOW.
A LEADING SHORTWAVE INTO THE SOUTHEAST ON TUESDAY INTO WEDNESDAY
MAY BRING SOME LIGHT AND SCATTERED RAIN. THEN THE INITIAL SYSTEM
IN CALIFORNIA SHOULD TRACK EAST DURING THE MIDDLE OF NEXT WEEK
WITH POTENTIAL TO SPAWN MODERATE CENTRAL PLAINS CYCLOGENESIS LATER
NEXT WEEK. LEAD RETURN GULF INFLOW INTO THE MS VALLEY AND VICINITY
MAY OFFER AN OPPORTUNITY FOR AN EXPANDING AREA OF MID TO LATE WEEK
RAINFALL ACROSS PORTIONS OF THE DEEP SOUTH/TENNESSEE VALLEY.
CONFIDENCE IS INCREASING FOR SOME SNOW AND ICE POTENTIAL ON THE
NORTHERN PERIPHERY OF THE PRECIPITATION SHIELD AS THE MOISTURE
FEEDS INTO A COOLED ANTECEDENT HIGH PRESSURE AIRMASS, BUT HIGH
UNCERTAINTY ON THE DETAILS ON AMOUNTS AND LOCATIONS. MODEST
RAINFALL MAY SPREAD INTO THE EASTERN U.S. AHEAD OF THE ATTENDANT
COLD FRONT. SOME IN THE FORM OF SNOW MAINLY INLAND AND NORTH, BUT
LOW CONFIDENCE ON AMOUNTS AND POTENTIAL IMPACTS.
THE WARMEST TEMPERATURE ANOMALIES WILL FEATURE ACROSS THE SOUTHERN
PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY TUESDAY-WEDNESDAY WHERE
DAYTIME HIGHS COULD BE 15 TO 20 DEGREES ABOVE NORMAL. WARMER THAN
AVERAGE CONDITIONS SHIFT INTO THE EASTERN THIRD OF THE NATION BY
THURSDAY, BUT SHOULD MODERATE AGAIN LATE WEEK ACROSS THE SOUTHEAST
TO MID-ATLANTIC WITH THE NEXT APPROACHING SYSTEM. UPPER RIDGING
BUILDING OVER THE CENTRAL U.S. WILL ALLOW FOR ANOTHER PERIOD OF
MODERATELY ABOVE AVERAGE READINGS FROM THE HIGH PLAINS/PLAINS INTO
THE MIDWEST AND GREAT LAKES INTO NEXT WEEKEND.
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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