502
FXUS02 KWBC 140700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST SAT JAN 14 2023
VALID 12Z TUE JAN 17 2023 - 12Z SAT JAN 21 2023
...ACTIVE PATTERN CONTINUES FOR THE WEST AND OTHER PARTS OF THE
LOWER 48 BUT WITH CENTRAL/SOUTHERN CALIFORNIA TRENDING DRIER
MID-LATE WEEK...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE MODELS AND ENSEMBLES CONTINUE TO SHOW AN INITIAL PATTERN
FEATURING A SEQUENCE OF PACIFIC SYSTEMS TRACKING INTO THE WEST AND
THEN NORTHEASTWARD BEYOND THE ROCKIES FOLLOWED BY A TRANSITION
TOWARD A BUILDING EASTERN PACIFIC UPPER RIDGE THAT WOULD LEAD TO
MEAN UPPER TROUGHING OVER THE INTERIOR LOWER 48, ALBEIT WITH SOME
UNCERTAINTY OVER THE CHARACTER OF THE TROUGH. THIS EVOLUTION WILL
LIKELY BEGIN A PERIOD OF DRIER WEATHER TO CENTRAL-SOUTHERN
CALIFORNIA AFTER MONDAY AND THEN THE REST OF THE STATE AFTER
ANOTHER SYSTEM BRINGS SOME RAIN/MOUNTAIN SNOW TO THE PACIFIC
NORTHWEST/NORTHERN CALIFORNIA AROUND MIDWEEK. THE CLIMATE
PREDICTION CENTER'S 8-14 DAY OUTLOOK CONTINUES TO SUGGEST THAT THE
DRIER PATTERN FOR CALIFORNIA WILL EXTEND BEYOND THE MEDIUM RANGE
PERIOD. THE DOMINANT SYSTEM OF INTEREST NEXT WEEK WILL CROSS THE
WEST WITH RAIN AND MOUNTAIN SNOW DURING THE FIRST HALF OF NEXT
WEEK AND SHOULD SPREAD A BROAD AREA OF SIGNIFICANT WEATHER ACROSS
PORTIONS OF THE CENTRAL-EASTERN U.S. WEDNESDAY-FRIDAY.
GUIDANCE NOW APPEARS FAIRLY AGREEABLE AND STABLE WITH THE ATLANTIC
SYSTEM REACHING JUST EAST OF MAINE BY EARLY TUESDAY AND THE SYSTEM
REACHING THE GREAT LAKES AT THE SAME TIME AND OPENING UP
THEREAFTER. THERE ARE STILL SIGNIFICANT UNCERTAINTIES WITH THE
SYSTEM CROSSING THE WEST ON TUESDAY AND CONTINUING NORTHEASTWARD
THE REST OF THE WEEK. GFS RUNS HAVE BEEN PARTICULARLY
INCONSISTENT OVER THE PAST 2-3 DAYS, EARLIER BEING AMONG THE
DEEPEST WITH THE SYSTEM OVER THE CENTRAL U.S. AND THEN STRAYING TO
THE WEAK/SUPPRESSED/PROGRESSIVE SIDE IN MOST RECENT RUNS, ONLY TO
HAVE THE 00Z RUN FINALLY COME BACK CLOSER TO THE MAJORITY CLUSTER.
SOME OF THE ISSUES IN THE GFS AND EVEN OTHER MODELS HAVE INVOLVED
FINE-SCALE (THUS HAVING LOW PREDICTABILITY) DETAILS OF SHORTWAVE
ENERGY ENTERING THE WEST DURING THE FIRST HALF OF THE WEEK.
PREFERENCE BASED ON 12Z/18Z DATA WAS TO MAINTAIN AN EVOLUTION
CLOSER TO THE ECMWF/CMC AND THEIR MEANS, WITH THE 12Z GFS/GEFS
MEAN AT LEAST SOMEWHAT CLOSER TO THAT IDEA THAN THE 18Z RUNS.
BEHIND THIS SYSTEM, MODELS AND INDIVIDUAL ENSEMBLE MEMBERS REMAIN
VARIED FOR HOW INCOMING TROUGH ENERGY WILL AMPLIFY OVER THE
WESTERN HALF OF THE COUNTRY, WITH 12Z/18Z GUIDANCE GENERALLY
REVERTING BACK TO A SLOWER/SHARPER TROUGH LIKE 24 HOURS AGO VERSUS
THE SOMEWHAT FASTER/BROADER TROUGH SEEN IN SOME OF YESTERDAY'S 00Z
CYCLE. A MODEL/MEAN BLEND ACCOUNTS FOR SOME BUT NOT ALL OF THIS
ADJUSTMENT, IN LIGHT OF RECENT OSCILLATIONS. LATEST GFS RUNS ARE
ON THE SHARP/AMPLIFIED SIDE OF THE SPREAD FOR A SHORTWAVE THAT MAY
ROUND THE TOP OF THE EASTERN PACIFIC RIDGE BY NEXT SATURDAY.
OVERALL GUIDANCE PREFERENCES LED TO THE FIRST HALF OF THE FORECAST
STARTING WITH AN OPERATIONAL MODEL COMPOSITE, INCLUDING LESS THAN
TYPICAL WEIGHT OF THE GFS (12Z RUN FOR WHAT WAS INCLUDED). THEN
THE BLEND ADJUSTED TOWARD AN EVEN WEIGHT OF MODELS/MEANS
(INCLUDING THE 12Z RUN FOR GEFS INPUT ALONG WITH THE 12Z ECMWF
MEAN) BY DAY 7 SATURDAY.
..WEATHER/HAZARD HIGHLIGHTS
THE SYSTEM MOVING THROUGH THE WEST ON TUESDAY SHOULD BRING RAIN
AND HIGHER ELEVATION SNOW ACROSS THE FOUR CORNERS STATES. THEN
EXPECT THIS SYSTEM TO BRING A VARIETY OF WEATHER TO THE CENTRAL
AND EASTERN U.S. MID-LATE WEEK. THIS INCLUDES THE POTENTIAL FOR
HEAVY RAINFALL OVER AND NEAR THE LOWER HALF OF THE MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND LOWER OHIO VALLEY. THE UPPER
DYNAMICS/LOW LEVEL GULF INFLOW AND GUIDANCE SIGNALS APPEAR
SUFFICIENTLY FAVORABLE TO DEPICT A SLIGHT RISK AREA ON THE DAY 5
EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK VALID 12Z WEDNESDAY-12Z
THURSDAY. SOME LOCALLY MODERATE TO HEAVY RAINFALL MAY EXTEND
FARTHER THROUGH THE EAST THEREAFTER BUT WITH LOWER CONFIDENCE IN
DETAILS. MEANINGFUL WINTRY WEATHER WILL BE POSSIBLE IN THE COLD
SECTOR, CURRENTLY MOST LIKELY ALONG AN AXIS FROM THE CENTRAL
PLAINS THROUGH THE GREAT LAKES AND NORTHEAST. DETAILS WILL DEPEND
ON THE STORM'S EXACT TRACK AND STRENGTH WHICH ARE YET TO BE
RESOLVED, SO SOME ADJUSTMENTS TO THE FORECAST WILL BE POSSIBLE.
WITH THE EVOLVING PATTERN CHANGE LATER IN THE PERIOD, THE NEXT
SYSTEM TO REACH THE WEST COAST WILL BRING ITS BRIEF PERIOD OF
LOCALLY MODERATE TO HEAVY RAINFALL/MOUNTAIN SNOW TO THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA AROUND MIDWEEK WITH LIGHTER
TOTALS THEN EXTENDING INTO THE ROCKIES. THE SOUTH MAY SEE A
REBOUND IN RAINFALL BY NEXT SATURDAY AS A FRONT LINGERING OVER THE
GULF LIFTS BACK NORTHWARD AHEAD OF AN APPROACHING COLD FRONT.
THE FORECAST PATTERN SHOULD MAINTAIN HIGHS 5-15F BELOW NORMAL OVER
THE SOUTHERN TWO-THIRDS OR SO OF THE WEST THROUGH THE PERIOD, WITH
READINGS CLOSE TO OR SLIGHTLY ABOVE NORMAL OVER THE FAR NORTH.
VERY WARM TEMPERATURES OVER THE EASTERN HALF OF THE COUNTRY SHOULD
ERODE FROM WEST TO EAST MID-LATE WEEK WITH SYSTEM/FRONTAL PASSAGE.
AHEAD OF THIS SYSTEM, EXPECT A BROAD AREA OF LOWS 15-25F ABOVE
NORMAL AND HIGHS 10-20F ABOVE NORMAL. MOST DAILY RECORDS SHOULD
BE FOR WARM LOWS, WHILE THE BEST CHANCE FOR RECORD HIGHS STILL
APPEARS TO BE OVER SOUTHEASTERN TEXAS AND LOWER MISSISSIPPI VALLEY
ON TUESDAY.
RAUSCH
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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