496
FXUS02 KWBC 120655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 AM EST THU JAN 12 2023
VALID 12Z SUN JAN 15 2023 - 12Z THU JAN 19 2023
...UNSETTLED AND ACTIVE PATTERN CONTINUES FOR WESTERN U.S. WITH
FOCUS ON CALIFORNIA ATMOSPHERIC RIVERS...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE FIRST IN A SERIES OF SHORTWAVES INTO THE WEST COAST THIS
PERIOD (SUNDAY-THURSDAY) WILL MOVE ONSHORE ON SUNDAY, AND QUICKLY
MOVE INTO THE CENTRAL U.S. BY MONDAY. MODEST SURFACE LOW
DEVELOPMENT IS EXPECTED WITH THIS SYSTEM AS IT MOVES INTO THE
MIDWEST AND EVENTUALLY GREAT LAKES. SOME MINOR TIMING DIFFERENCES,
BUT MODELS GENERALLY SHOW GOOD AGREEMENT WITH THIS SYSTEM ALLOWING
FOR A GENERAL MODEL BLEND FOR TONIGHTS MANUAL FORECAST PROGS.
QUICKLY ON ITS HEELS, ANOTHER SHORTWAVE MOVES INTO SOUTHERN
CALIFORNIA AROUND MONDAY-TUESDAY NEXT WEEK THIS TIME WITH PLENTY
MORE UNCERTAINTY. THE UKMET AND ECMWF WERE FARTHEST SOUTH WITH THE
SYSTEM INTO CALIFORNIA WITH THE GFS AND CMC NOTICEABLY NORTH. THIS
NORTHERN IDEA SEEMED BETTER REPRESENTED BY THE ENSEMBLE MEANS AS
WELL. THE UKMET, BEING THE FARTHEST SOUTH, WAS NOT USED IN
TONIGHTS BLEND. AS THE SYSTEM PROCEEDS INTO THE SOUTHWEST AND THE
CENTRAL U.S. EARLY NEXT WEEK, IT'S LIKELY TO SPAWN AN ADDITIONAL
MODESTLY DEEPENING LOW PRESSURE SYSTEM WHICH TRACKS INTO THE
MIDWEST NEXT THURSDAY. THERE IS MORE UNCERTAINTY WITH RESPECT TO
AMPLITUDE OF THE SHORTWAVE INTO THE CENTRAL U.S., WHICH OBVIOUSLY
HAS IMPLICATIONS FOR SYSTEM STRENGTH MID TO LATE NEXT WEEK. THE
WPC PROGS FAVORED A BLEND CLOSER TO THE (EXPECTEDLY WEAKER)
ENSEMBLE MEANS TO MITIGATE THE DIFFERENCES, BUT DID INCORPORATE 50
PERCENT TOTAL OF THE STRONGER ECMWF AND LESS AMPLIFIED GFS FOR A
LITTLE BIT OF ADDED SYSTEM DEFINITION. A LOOK AT THE INCOMING 00Z
GUIDANCE (AVAILABLE AFTER FORECAST GENERATION TIME) SHOWS THE GFS
HAS TRENDED TOWARDS THE STRONGER 18Z (YESTERDAY) AND TODAYS 00Z
ECMWF WITH A CLOSED LOW OVER THE MID-MISSISSIPPI VALLEY NEXT
THURSDAY, ALTHOUGH THE 00Z CMC STILL SHOWS A WEAKER SHORTWAVE.
THIS POSSIBLE TREND TOWARDS A STRONGER SOLUTION WILL NEED TO BE
MONITORED OVER THE COMING DAYS.
YET ANOTHER SHORTWAVE LOOKS TO TARGET THE PACIFIC NORTHWEST AROUND
WEDNESDAY NEXT WEEK, BUT THERE IS AGAIN A LOT OF TIMING AND
STRENGTH DIFFERENCES WITH THIS, SO A BLEND TOWARDS THE BETTER
AGREEABLE ENSEMBLE MEANS WAS REASONABLE FOR NOW FOR THIS LATE
PERIOD SYSTEM.
..WEATHER/HAZARD HIGHLIGHTS
THE WEST WILL REMAIN ACTIVE AS A SERIES OF SHORTWAVES CONTINUES TO
DIRECT UNNEEDED ADDITIONAL HEAVY RAINFALL AND MOUNTAIN SNOWS
TOWARDS PARTICULARLY CALIFORNIA, BUT ALSO THE PACIFIC NORTHWEST.
THE FIRST IN THIS SERIES OF EXTENDED RANGE STORMS WILL ARRIVE ON
SATURDAY JUST BEFORE THE START OF THIS FORECAST PERIOD, AND THE
HEAVIEST OF THE PRECIPITATION SHOULD BE OVER BY SUNDAY AS THE
OVERALL UPPER SYSTEM MOVES INLAND. STILL, ANY LINGERING RAINFALL
OVER AN ALREADY VERY OVER-SATURATED CALIFORNIA MAY CONTINUE TO
WORSEN FLOODING OR DELAY IMPROVEMENT OF ONGOING ISSUES. RAIN AND
HIGHER ELEVATION SNOWS ARE POSSIBLE IN THE SOUTHWEST ON SUNDAY,
AND EVENTUALLY RETURN FLOW OUT OF THE GULF OF MEXICO MAY INCREASE
PRECIPITATION CHANCES INTO THE PLAINS/MIDWEST AS WELL EARLY NEXT
WEEK. THE NEXT IN THE SERIES SHOULD ARRIVE EARLY NEXT WEEK AGAIN
POSSIBLY EXACERBATING PROBLEMS ACROSS CALIFORNIA AS IT DELIVERS
MORE MOISTURE INTO THE REGION. HEAVY RAINFALL COULD DEVELOP OUT
INTO THE PLAINS-MISSISSIPPI VALLEY-MIDWEST AGAIN ALONG THE
ATTENDANT COLD FRONT NEXT WEDNESDAY, POSSIBLY HEAVY IF A STRONGER
STORM MANIFESTS. THERE COULD BE A CHANCE FOR SOME SNOW/ICE TOO IN
THE NORTHERN PERIPHERY OF THE STORM, AMOUNTS AGAIN HIGHLY
DEPENDENT ON STORM STRENGTH.
ABOVE NORMAL TEMPERATURES WILL MOVE EAST WITH TIME FROM THE
CENTRAL U.S. THIS WEEKEND INTO THE MIDWEST AND EVENTUALLY THE EAST
EARLY NEXT WEEK. THE GREATEST ANOMALIES SHOULD FOCUS ACROSS THE
DEEP SOUTH INTO THE MIDWEST WITH DAYTIME HIGHS 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 GENERALLY
ACROSS THE SAME REGION FROM SUNDAY ONWARD. DAYTIME HIGHS ACROSS
THE WEST AND SOUTHWEST SHOULD BE NEAR OR BELOW NORMAL AMIDST
PLENTY OF CLOUDS AND RAINY CONDITIONS.
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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