194
FXUS02 KWBC 090648
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EST MON JAN 09 2023
VALID 12Z THU JAN 12 2023 - 12Z MON JAN 16 2023
...CALIFORNIA REMAINS ACTIVE INTO EARLY NEXT WEEK 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. DURING THE MEDIUM RANGE
PERIOD LOOKS TO STAY RATHER AMPLIFIED BUT PROGRESSIVE. A VERY
ACTIVE EAST PACIFIC WILL CONTINUE TO TARGET AN ALREADY VERY
SATURATED CALIFORNIA WITH MORE ROUNDS OF HEAVY RAIN AND MOUNTAIN
SNOW POTENTIAL AS A COUPLE OF SHORTWAVES TRAVERSE THE REGION THIS
WEEKEND. IN THE CENTRAL U.S., NORTHERN AND SOUTHERN STREAM ENERGY
SHOULD COMBINE ALLOWING FOR AMPLIFIED TROUGHING THROUGH THE EAST
LATER THIS WEEK AND POSSIBLE SURFACE LOW DEVELOPMENT WELL OFF THE
NORTHEAST COAST NEXT WEEKEND. THE SECOND SHORTWAVE INTO SOUTHERN
CALIFORNIA THIS WEEKEND WILL QUICKLY MOVE INTO THE SOUTHERN PLAINS
EARLY NEXT WEEK WHILE YET ANOTHER SHORTWAVE/UPPER TROUGH LOOMS OFF
THE WEST COAST.
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 AMPLIFIED TROUGH INTO THE EAST AND ANY
SORT OF POSSIBLE SURFACE LOW DEVELOPMENT OFF THE NORTHEAST COAST.
THE LATEST GUIDANCE SUITE HAS TRENDED FASTER AND MORE OPEN WITH
THIS SYSTEM IN THE PAST DAY OR SO, BUT STILL CONTINUE TO OFFER A
LOT OF DIFFERENCES IN THE DETAILS WHICH WOULD HAVE IMPLICATIONS
FOR ASSOCIATED PRECIPITATION WITH THIS SYSTEM. OUT WEST, THE
DETERMINISTIC MODELS SHOW GOOD AGREEMENT WITH TIMING OF THE FIRST
SHORTWAVE INTO CALIFORNIA, BUT DO HAVE SOME TIMING VARIABILITY
WITH THE NEXT ONE RIGHT ON ITS HEELS. THE BIGGEST OUTLIER WITH
THIS (AT LEAST THROUGH THE 12Z/18Z RUNS FROM 1/8) IS THE CMC WHICH
BRINGS A CLOSED LOW MUCH FARTHER SOUTH THAN THE BETTER GUIDANCE
ENVELOPE RESULTING IN AN OVERALL SLOWER PROGRESSION OF THE SYSTEM
INTO THE SOUTHWEST. THERE ARE SOME TIMING DIFFERENCES WITH THE GFS
AND ECMWF BUT A BLEND OF THESE MODELS WITH THE ENSEMBLE MEANS
PROVIDED A GOOD STARTING POINT CONSIDERING THIS IS STILL IN THE
DAY 6-7 TIME FRAME. PLENTY OF DIFFERENCES UPSTREAM TOO WITH THE
NEXT UPPER LOW IN THE GULF OF ALASKA AND VARIOUS PIECES OF
SHORTWAVE ENERGIES ROUNDING SOUTH TOWARDS THE NORTHWEST COAST.
ENOUGH AGREEMENT THROUGH DAY 5/SATURDAY ACROSS THE BOARD ALLOWED
FOR A SIMPLE BLEND OF THE LATEST DETERMINISTIC GUIDANCE FOR
TONIGHTS WPC FORECAST WHICH DID ALSO MAINTAIN GOOD CONTINUITY WITH
THE PREVIOUS SHIFT. AFTER THAT, LEANED MORE ON THE GFS/ECMWF ALONG
WITH THE ENSEMBLE MEANS TO HELP SMOOTH OUT THE TIMING AND DETAIL
DIFFERENCES IN THE WEST ESPECIALLY.
..WEATHER/HAZARD HIGHLIGHTS
THE BIG WEATHER STORY THROUGH THE PERIOD WILL REMAIN OUT WEST AS A
PARADE OF STORMS/ATMOSPHERIC RIVERS CONTINUE TAKE AIM AT AN
ALREADY OVER SATURATED CALIFORNIA. THE NEXT IN THE SERIES WILL BE
ONGOING AS THE PERIOD BEGINS THURSDAY, BUT DOES NOT LOOK NEARLY AS
IMPACTFUL/WIDESPREAD AS SOME OF THE PREVIOUS STORMS OVER THE PAST
WEEK. STILL, THERE IS POTENTIAL FOR AT LEAST LOCALLY HEAVY RAINS
ACROSS NORTHERN CALIFORNIA, WHERE MANY AREAS ARE ALREADY VERY
SENSITIVE TO ADDITIONAL RAINFALL. MOISTURE SHOULD ALSO REACH INTO
PARTS OF THE PACIFIC NORTHWEST BRINGING COASTAL RAIN AND MOUNTAIN
SNOWS. THERE MAY BE A BRIEF BREAK ON FRIDAY IN THE RAINFALL, BUT
THE NEXT STORM WILL APPROACH THE WEST COAST ON SATURDAY, THIS TIME
LIKELY TO IMPACT A LARGER AREA OF CALIFORNIA WITH EVEN MORE HEAVY
PRECIPITATION POTENTIAL. FLOODING CHANCES WILL INCREASE AGAIN
ACROSS COASTAL CENTRAL TO SOUTHERN CALIFORNIA WITH ANOTHER ROUND
OF HEAVY SNOWS FOR THE SIERRA MOUNTAINS. 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.
A DEVELOPED LOW PRESSURE SYSTEM THROUGH THE MIDWEST AND INTO THE
EAST WILL SPREAD RAIN, LOCALLY HEAVY, ACROSS THE DEEP SOUTH AND
MUCH OF THE EASTERN U.S. LATER THIS WEEK. GUIDANCE CONTINUES TO
SHOW SOME POTENTIAL FOR SNOW AND ICE ON THE NORTHERN PERIPHERY OF
THE PRECIPITATION SHIELD, BUT NOT LIKELY TO BE ANYTHING
SIGNIFICANT. AS THE LOW MOVES INTO THE NORTHEAST, HEAVY RAIN LOOKS
LIKELY ACROSS EASTERN/COASTAL NEW ENGLAND, BUT SOME ACCUMULATING
SNOW IS POSSIBLE WELL INLAND, ESPECIALLY IN THE HIGHER TERRAIN.
WARMER THAN AVERAGE TEMPERATURES AHEAD OF THE EASTERN U.S. SYSTEM
WILL SPREAD ACROSS THE EASTERN THIRD OF THE NATION WITH DAYTIME
HIGHS 10 TO 20 DEGREES ABOVE NORMAL ON THURSDAY. TEMPERATURES WILL
TREND COOLER AND BACK TOWARDS NORMAL WITH SYSTEM PASSAGE INTO THE
WEEKEND. UPPER RIDGING BUILDING OVER THE CENTRAL U.S. AND STEADILY
PROGRESSING EAST WITH TIME WILL ALLOW FOR MODERATELY ABOVE AVERAGE
READINGS FROM THE HIGH PLAINS/PLAINS INTO THE MIDWEST AND THE
GREAT LAKES INTO EARLY NEXT WEEK.
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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