101
FXUS02 KWBC 080659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST SUN JAN 08 2023
VALID 12Z WED JAN 11 2023 - 12Z SUN JAN 15 2023
...CALIFORNIA REMAINS ACTIVE INTO NEXT WEEKEND AS A SERIES OF
ATMOSPHERIC RIVERS BRINGS HEAVY RAIN AND MOUNTAIN SNOW...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE WEATHER PATTERN OVER MUCH OF THE U.S. SHOULD REMAIN
PROGRESSIVE BUT ACTIVE, AND TRENDING MORE AMPLIFIED, THROUGH AT
LEAST NEXT WEEKEND. A VERY ACTIVE EAST PACIFIC WILL CONTINUE TO
TARGET AN ALREADY VERY SATURATED CALIFORNIA WITH MORE HEAVY RAIN
AND MOUNTAIN SNOW POTENTIAL AS TROUGHING BUILDS OFFSHORE LATER
THIS WEEK WITH ANOTHER SHORTWAVE MOVING INLAND NEXT WEEKEND. A
SHORTWAVE INITIALLY IN THE FOUR CORNERS REGION ON WEDNESDAY WILL
SHIFT EAST, WITH GUIDANCE CONTINUING TO SUGGEST A COMPACT CLOSED
UPPER LOW LIKELY OVER THE MISSISSIPPI VALLEY BY THURSDAY. NORTHERN
STREAM ENERGY ACROSS THE GREAT LAKES MAY COMBINE WITH THIS SYSTEM
TO AMPLIFY THE TROUGH OVER THE EAST, EVENTUALLY ALLOWING FOR LOW
PRESSURE DEVELOPMENT OFF THE NORTHEAST COAST NEXT WEEKEND.
THE LATEST GUIDANCE CONTINUES TO AGREE ON THE OVERALL SYNOPTIC
PATTERN, BUT THERE ARE A LOT OF UNCERTAINTIES IN THE TIMING AND
DETAILS OF ESPECIALLY THE CLOSED LOW/AMPLIFIED TROUGH IN THE EAST
AND ANY SORT OF POSSIBLE NOR'EASTERN OFF THE NORTHEAST COAST THE
SECOND HALF OF THE PERIOD. THE LATEST 00Z GFS (AVAILABLE AFTER
FORECAST GENERATION TIME) IS SIGNIFICANTLY FASTER WITH THIS
FEATURE THROUGH THE MIDWEST, A FAVORABLE TREND GIVEN THE REST OF
THE GUIDANCE, BUT DOES DIFFER QUITE A BIT FROM ITS PREVIOUS RUN
WITH THE EVOLUTION OVER THE EASTERN U.S. NEXT WEEKEND. THE REST OF
THE GUIDANCE SHOWS A LOT OF UNCERTAINTY IN THE INTERACTION BETWEEN
THIS SYSTEM AND WEAKER NORTHERN STREAM ENERGY LATE PERIOD
RESULTING IN A LOT OF MODEL RUN TO RUN VARIABILITY. GIVEN THERE
ARE MORE QUESTIONS THAN ANSWERS HERE IN THE EAST LATE PERIOD, IT
SEEMS PRUDENT TO LEAN ON THE ENSEMBLE MEANS, WHICH AT LEAST
PRESENT A REASONABLY BLENDED AND MIDDLE GROUND SOLUTION. OUT WEST,
THERE IS AGAIN GOOD LARGE SCALE AGREEMENT OFF THE WEST COAST, BUT
TIMING DIFFERENCES AS A COUPLE OF SHORT WAVES CROSS INTO
CALIFORNIA NEXT WEEKEND.
ENOUGH AGREEMENT ON DAYS 3 AND 4 ALLOWED FOR A SIMPLE BLEND OF THE
LATEST DETERMINISTIC GUIDANCE FOR TONIGHTS WPC FORECAST. AFTER
THAT, LEANED MORE HEAVILY ON THE ENSEMBLE MEANS TO HELP MITIGATE
THE DIFFERENCES ESPECIALLY IN THE EAST. DESPITE THE RUN TO RUN
VARIABILITY IN THE MODELS, THIS APPROACH DID HELP MAINTAIN GOOD
CONTINUITY WITH THE PREVIOUS SHIFT.
..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. THE NEXT IN THE SERIES LOOKS TO BEGIN WEDNESDAY,
THOUGH SHOULD NOT BE QUITE AS STRONG OR IMPACTFUL AS THE ONE
FORECAST DURING THE SHORT RANGE PERIOD. EVEN STILL, THERE IS
POTENTIAL FOR AT LEAST LOCALLY HEAVY RAINS MAINLY ACROSS NORTHERN
CALIFORNIA, WHERE MANY AREAS ARE ALREADY VERY SENSITIVE TO
ADDITIONAL RAINFALL. THERE MAY BE A BRIEF BREAK LATE NEXT WEEK,
BUT THE NEXT AR TO IMPACT THE REGION SHOULD COME IN AROUND NEXT
WEEKEND AND SHIFT SOUTHWARD ALONG THE COAST BRINGING AGAIN MORE
HEAVY RAINFALL, FLOODING, AND MOUNTAIN SNOW THREATS TO THE STATE.
TO THE NORTH, RAIN AND MOUNTAIN SNOWS ARE ALSO LIKELY ACROSS THE
PACIFIC NORTHWEST WITH ADDITIONAL SHORTWAVE ENERGY.
A SHORTWAVE THROUGH THE FOUR CORNERS ON WEDNESDAY SHOULD SPAWN
MODERATE CENTRAL PLAINS CYCLOGENESIS THAT TRACKS EAST-NORTHEAST
THROUGH THE MIDWEST INTO FRIDAY. 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. GUIDANCE SHOWS POTENTIAL FOR SOME SNOW AND
ICE 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 AND ALSO AS ADDITIONAL LOW PRESSURE DEVELOPES OFF THE
EAST COAST. SOME IN THE FORM OF SNOW MAINLY WELL INLAND AND NORTH,
BUT LOW CONFIDENCE ON AMOUNTS AND POTENTIAL IMPACTS. ALTHOUGH,
WITH A LACK OF FAVORABLE UPPER LEVEL BLOCKING FEATURES AND AN
APPRECIABLY COLD AIR MASS IN PLACE, THIS EVENT LOOKS TO BE MORE OF
A RAIN THAN SNOW EVENT FOR MANY IN THE NORTHEAST.
THE WARMEST TEMPERATURE ANOMALIES WILL FEATURE ACROSS THE SOUTHERN
PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY ON 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 WHILE RAIN AND
CLOUDS KEEP MOST OF THE WEST COAST NEAR NORMAL.
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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