702
FXUS02 KWBC 130659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST FRI JAN 13 2023
VALID 12Z MON JAN 16 2023 - 12Z FRI JAN 20 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
LATEST GUIDANCE SHOWS A CONTINUED PROGRESSION OF PACIFIC SYSTEMS
THAT WILL BRING PRECIPITATION INTO THE WEST AND THEN TO AREAS EAST
OF THE ROCKIES AS LOW PRESSURE TRACKS NORTHEASTWARD FROM THE
PLAINS. A NOTABLE ASPECT OF NEXT WEEK'S EVOLUTION SHOULD BE
AMPLIFICATION OF AN EASTERN PACIFIC UPPER RIDGE THAT WOULD FOCUS
WEST COAST PRECIPITATION MORE OVER THE PACIFIC NORTHWEST WHILE AT
LEAST CENTRAL-SOUTHERN CALIFORNIA SEES DRIER CONDITIONS. THIS MAY
BE THE BEGINNING OF A LONGER TERM DRIER PERIOD OVER THE
SOUTHWESTERN STATES BASED ON THE CLIMATE PREDICATION CENTER 8-14
DAY OUTLOOK.
LOOKING AT INDIVIDUAL SYSTEMS, THE FIRST FEATURE OF NOTE IS A
WESTERN ATLANTIC UPPER LOW WHOSE NORTHWARD MOTION INTO THE
CANADIAN MARITIMES MONDAY-TUESDAY COULD BRING LOW PRESSURE ON A
TRACK JUST EAST OF MAINE, WITH RECENT WESTWARD TRENDS BRINGING
SOMEWHAT MORE MOISTURE INTO THAT STATE. BEHIND THIS SYSTEM WILL BE
LOW PRESSURE FORECAST TO TRACK FROM THE PLAINS INTO THE GREAT
LAKES EARLY IN THE WEEK AND THEN BECOMING INCORPORATED INTO THE
BROADER CIRCULATION UNDERNEATH THE LEADING SYSTEM. MEANWHILE
VIGOROUS LOW PRESSURE REACHING CALIFORNIA ON MONDAY SHOULD REACH
THE PLAINS BY WEDNESDAY AND THEN CONTINUE INTO THE GREAT
LAKES/NORTHEAST. THE MAIN GUIDANCE CONSIDERATION ARISES AFTER
EARLY DAY 6 THURSDAY AS THE 18Z/00Z GFS RUNS OPEN UP AND
ACCELERATE THE SYSTEM TO AN INCREASING EXTENT VERSUS ECMWF/CMC
RUNS (INCLUDING THE NEW 00Z VERSIONS) AND THE 12Z ECMWF MEAN. THE
00Z GEFS MEAN (TRENDING FASTER THAN PRIOR GEFS RUNS) AND 12Z CMC
MEAN OFFER SUPPORT FOR THE 18Z/00Z GFS RUNS BUT THE GFS SEEMS TO
HINGE ON LOW-CONFIDENCE INTERACTION INVOLVING SOUTHERN CANADA
SHORTWAVE ENERGY. FINALLY, GUIDANCE SHOWS A GOOD SIGNAL IN
PRINCIPLE FOR THE NEXT SHORTWAVE THAT SHOULD REACH THE NORTHWEST
AROUND MIDWEEK AND THEN AMPLIFY INLAND AS EASTERN PACIFIC RIDGING
BUILDS. THE 18Z/00Z GFS AND 12Z ECMWF (AND TO A REASONABLE DEGREE
12Z CMC) MATCH UP WITH THE MEANS FAIRLY WELL INTO FRIDAY. THE 12Z
GFS WAS A TAD SLOW WHILE THE NEW 00Z CMC HAS STRAYED A LITTLE
BROADER AND FASTER THAN CONSENSUS WITH THE SHORTWAVE. THE 00Z
ECMWF HAS BECOME BROADER WITH THIS SHORTWAVE TOO, ILLUSTRATING
CURRENT UNCERTAINTY WITH THE SPECIFICS.
BASED ON THE 12Z/18Z ARRAY OF GUIDANCE, THE UPDATED FORECAST
UTILIZED A 12Z/18Z OPERATIONAL MODEL COMPOSITE FOR THE FIRST HALF
OF THE PERIOD AND THEN TRANSITIONED TO A MODEL/ENSEMBLE MEAN BLEND
THEREAFTER. BY LATE IN THE PERIOD, GFS INPUT WAS SPLIT BETWEEN THE
12Z/18Z RUNS TO INCORPORATE A LITTLE OF THE MORE PREFERRED 12Z RUN
OVER/NEAR THE NORTHEAST WHILE ALSO KEEPING SOME OF THE MORE
FAVORED 18Z RUN OVER THE WEST.
..WEATHER/HAZARD HIGHLIGHTS
WHAT SHOULD BE THE LAST IN THE SERIES OF SIGNIFICANT STORM SYSTEMS
TO AFFECT MOST OF CALIFORNIA WILL LIKELY REACH THE STATE ON MONDAY
WITH ADDITIONAL HEAVY RAINFALL AND MOUNTAIN SNOW, WITH HIGHEST
TOTALS OVER THE SIERRA NEVADA AND TO A LESSER DEGREE ALONG FAVORED
COASTAL AREAS. RAINFALL OVER ALREADY VERY OVER-SATURATED GROUND
MAY CONTINUE TO WORSEN FLOODING OR DELAY IMPROVEMENT OF ONGOING
ISSUES. EXPECT THIS MOISTURE TO BRING RAIN AND HIGHER ELEVATION
SNOW INTO THE SOUTHWEST/SOUTHERN ROCKIES EARLY IN THE WEEK AS
WELL, WITH HIGHEST TOTALS OVER FAVORED TERRAIN IN ARIZONA AND
SOUTHWESTERN UTAH. THE NEXT SYSTEM WILL FOCUS RAIN AND MOUNTAIN
SNOW MORE OVER THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA
AROUND TUESDAY-WEDNESDAY, WITH MUCH LIGHTER AMOUNTS REACHING
INLAND OVER THE WEST THEREAFTER. CENTRAL-SOUTHERN CALIFORNIA
SHOULD STAY FAIRLY DRY.
TO THE EAST OF THE ROCKIES, A SYSTEM TRACKING FROM THE WESTERN
ATLANTIC NORTHWARD INTO THE CANADIAN MARITIMES MAY BRING SOME
WINTRY WEATHER TO NORTHERN NEW ENGLAND EARLY IN THE WEEK. THE
FIRST OF TWO PLAINS-GREAT LAKES SYSTEMS SHOULD BRING MODERATE
AMOUNTS OF PRECIPITATION TO THE EASTERN HALF OF THE COUNTRY EARLY
IN THE WEEK, WITH ANY SNOW LIKELY LIMITED TO FAR NORTHERN AREAS.
THE SECOND SYSTEM SHOULD BRING A BROADER AREA OF HEAVIER
PRECIPITATION TO AREAS FROM THE PLAINS EASTWARD MID-LATE WEEK.
WITH TYPICAL SENSITIVITY TO EXACT TRACK, BEST SNOW POTENTIAL
CURRENTLY EXISTS FROM THE CENTRAL HIGH PLAINS THROUGH THE UPPER
MIDWEST, PARTS OF THE GREAT LAKES, AND NEW ENGLAND. MEANWHILE GULF
INFLOW MAY BE SUFFICIENT TO SUPPORT SOME AREAS OF HEAVY RAINFALL
OVER AND NEAR PORTIONS OF THE MISSISSIPPI VALLEY AND OHIO VALLEY.
WHILE SYSTEM PROGRESSION WILL PROVIDE SOME DAY-TO-DAY VARIABILITY
TO TEMPERATURES, THE OVERALL PATTERN SHOULD SUPPORT WELL ABOVE
NORMAL TEMPERATURES OVER MUCH OF THE EASTERN HALF OF THE COUNTRY
AND BELOW NORMAL TEMPERATURES OVER THE SOUTHERN TWO-THIRDS OF THE
WEST. THE WARMTH EAST OF THE ROCKIES WILL LIKELY ERODE SOMEWHAT
FROM WEST TO EAST WITH THE PASSAGE OF THE COLD FRONT ANCHORED BY
THE MID-LATE WEEK STORM. SOME AREAS MAY SEE ONE OR MORE DAYS WITH
MORNING LOWS 20-30F ABOVE NORMAL, AND POTENTIAL FOR WARM LOW DAILY
RECORDS MIGRATING FROM THE EASTERN PLAINS/MISSISSIPPI VALLEY INTO
THE EAST. HIGHS SHOULD BE A LITTLE LESS EXTREME WITH MERE POCKETS
OF PLUS 20-25F ANOMALIES, WHILE BEST POTENTIAL FOR ANY RECORD
HIGHS EXISTS OVER/NEAR SOUTHEASTERN TEXAS ON TUESDAY. THE SOUTHERN
TWO-THIRDS OR SO OF THE WEST WILL TEND TO SEE HIGHS 5-15F BELOW
NORMAL.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page