022
FXUS02 KWBC 151900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST SUN JAN 15 2023
VALID 12Z WED JAN 18 2023 - 12Z SUN JAN 22 2023
...MID-LATE WEEK STORM SYSTEM LIKELY TO BRING A VARIETY OF
SIGNIFICANT WEATHER TO THE CENTRAL/EASTERN U.S...
..OVERVIEW
LATEST GUIDANCE STILL SHOWS A SIGNIFICANT PATTERN CHANGE EXPECTED
TO TAKE PLACE THIS WEEK THROUGH THE WEEKEND, WITH A STEADILY
BUILDING EASTERN PACIFIC UPPER RIDGE PROMOTING THE DEVELOPMENT OF
A POSITIVELY TILTED MEAN TROUGH OVER THE LOWER 48 BY THE LATE
WEEK/WEEKEND TIME FRAME. THIS EVOLUTION SHOULD LEAD TO A PERIOD OF
DRIER WEATHER OVER CALIFORNIA/SOUTHWESTERN U.S. WITH THE RIDGE
DIVERTING MOST INCOMING PACIFIC MOISTURE FARTHER NORTH AND THEN
INTO THE INTERIOR WEST/ROCKIES AS SHORTWAVE ENERGY DROPS INTO THE
MEAN TROUGH. AHEAD OF THIS TRANSITION, THE FINAL SYSTEM REACHING
SOUTHERN CALIFORNIA IN THE SHORT RANGE PERIOD WILL LIKELY EMERGE
OVER THE PLAINS ON WEDNESDAY AND TRACK NORTHEASTWARD THEREAFTER.
THIS AREA OF LOW PRESSURE MAY BRING A BAND OF MEANINGFUL SNOW TO
THE NORTH/WEST OF ITS TRACK AND THE POTENTIAL FOR HEAVY
RAINFALL/STRONG CONVECTION IN PORTIONS OF THE WARM SECTOR. THE
SOUTHEASTERN QUADRANT OF THE LOWER 48 COULD SEE ANOTHER EPISODE OF
POSSIBLY HEAVY RAINFALL BY NEXT WEEKEND, DEPENDING ON DETAILS OF
UPSTREAM SHORTWAVE ENERGY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOLLOWING THE PATTERN OF RECENT MODEL/ENSEMBLE RUNS, THERE IS GOOD
AGREEMENT ON THE LARGE SCALE PATTERN EVOLUTION BUT CONTINUED
MEANINGFUL DETAIL DIFFERENCES FOR INDIVIDUAL FEATURES. ONE SUCH
FEATURE IS THE SURFACE LOW TRACKING FROM THE PLAINS EASTWARD INTO
THE MIDDLE MISSISSIPPI/OHIO VALLEYS WEDNESDAY-THURSDAY. OVERALL
MODELS HAVE TRENDED FASTER WITH THE LOW IN THE 00/06Z MODEL CYCLE
AND PERSISTING INTO THE NEWER 12Z MODELS, WITH THE EXCEPTION OF
MANY GFS RUNS THAT HAVE BEEN ON THE SLOWER SIDE. THE 00Z GFS
SEEMED TO BE IN BETTER ALIGNMENT WITH OTHER GUIDANCE THAN THE
06Z/12Z RUNS. THE SPEED OF THE SURFACE LOW AND ITS EXACT TRACK
WILL AFFECT THE FORECAST FOR SNOW ON THE NORTHERN SIDE. WINTER
WEATHER PROBABILITIES THUS SHIFTED NORTHEAST FROM THE PREVIOUS
FORECAST IN CONJUNCTION WITH THE SHORT RANGE WINTER WEATHER DESK.
BY AROUND THURSDAY, MODELS FAVOR SHORTWAVE ENERGY DROPPING INTO
THE WEST, BUT SOLUTIONS VARY ON HOW DEEP THE ENERGY DIVES. GFS
RUNS AND GEFS MEMBERS SHOW A DIVE FARTHER SOUTH, BRINGING
PRECIPITATION TO THE SOUTHERN HALF OF THE INTERIOR WEST, WHILE 00Z
CMC/EC SOLUTIONS ARE FARTHER NORTH WITH THE ENERGY/500MB HEIGHTS
AND THE PRECIPITATION. BY FRIDAY-SATURDAY, MODELS VARY WITH THE
CLOSING OFF OF A LOW WITHIN THE POSITIVELY TILTED TROUGH, BUT AT
LEAST ARE GENERALLY AGREEABLE FOR A GRADUAL SHIFT EASTWARD. BUT BY
SUNDAY CONSIDERABLY MORE DIFFERENCES ARISE WITH THE TROUGH AS
CENTRAL CANADA SHORTWAVE ENERGY MAY PHASE WITH THE TROUGH (00Z EC)
OR RUSH EASTWARD WITHOUT PHASING (GFS RUNS). ADDITIONALLY, MAJOR
DIFFERENCES UPSTREAM PLAY A ROLE--NAMELY ANOTHER ROUND OF ENERGY
PERHAPS SPILLING SOUTH INTO THE NORTHWEST, SERVING TO ERODE THE
EASTERN EDGE OF THE RIDGE/SHIFT THE RIDGE WESTWARD, WHICH MOST
MODELS SHOW OTHER THAN THE ECMWF/EC ENSEMBLE MEANS. ALL THESE
DIFFERENCES ALOFT LEAD TO UNCERTAINTIES WITH FRONTAL POSITIONS
ACROSS THE SOUTH-CENTRAL AND SOUTHEASTERN U.S. AND POTENTIAL FOR
HEAVY RAINFALL. GIVEN THIS VARIETY IN SOLUTIONS, CONFIDENCE GOES
DOWN BY NEXT WEEKEND WITH THE PATTERN.
THE WPC FORECAST UTILIZED A MULTI-MODEL BLEND OF MAINLY 00Z
DETERMINISTIC GUIDANCE EARLY IN THE PERIOD, GIVEN THE 06Z GFS
SURFACE LOW POSITION SEEMED SLOW AS MENTIONED EARLIER, BUT DID NOT
NECESSARILY FAVOR THE 00Z GFS'S RAINFALL AXIS IN THE WARM SECTOR
WEDNESDAY-THURSDAY. GRADUALLY BLENDED IN AND TRENDED UP THE
ENSEMBLE MEANS FOR DAYS 5-7. THE 00Z CMC MEAN SEEMED LIKE A GOOD
MIDDLE GROUND BETWEEN THE EC MEAN THAT STAYED AMPLIFIED IN THE
WEST AND THE GEFS MEAN SHOWING DIGGING ENERGY.
..WEATHER/HAZARD HIGHLIGHTS
THE SYSTEM EXPECTED TO TRACK THROUGH THE PLAINS AND MIDWEST INTO
THE NORTHEAST WEDNESDAY-FRIDAY SHOULD BRING A VARIETY OF
SIGNIFICANT WEATHER TO THE CENTRAL AND EASTERN U.S. LOCATIONS TO
THE NORTH AND WEST OF THE STORM TRACK WILL LIKELY SEE A BAND OF
MEANINGFUL SNOW, WITH RECENT FORECASTS SUGGESTING A MOST LIKELY
AXIS FROM THE CENTRAL HIGH PLAINS THROUGH THE GREAT LAKES AND THE
INTERIOR NORTHEAST. FARTHER SOUTH IN THE WARM SECTOR, THERE WILL
BE THE POTENTIAL FOR HEAVY RAINFALL WITH A SLIGHT RISK AREA
DEPICTED ON THE DAY 4 (12Z WEDNESDAY-12Z THURSDAY) EXPERIMENTAL
EXCESSIVE RAINFALL OUTLOOK ACROSS PARTS OF THE LOWER MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND LOWER OHIO VALLEY. THE STORM
PREDICTION CENTER IS MONITORING THE POTENTIAL FOR SEVERE
THUNDERSTORMS OVER/NEAR THE LOWER MISSISSIPPI VALLEY IN THIS TIME
FRAME AS WELL. SOME MODERATE TO HEAVY RAINFALL MAY EXTEND FARTHER
THROUGH THE EAST AFTER WEDNESDAY BUT SHOULD BECOME MORE LOCALIZED
AS THE BEST DYNAMICS LIFT NORTHEASTWARD. CONTINUE TO MONITOR
FORECASTS AS GUIDANCE EVENTUALLY RESOLVES SOME OF THE FINER
DETAILS OF THIS SYSTEM. WITH THE EVOLVING PATTERN CHANGE LATER IN
THE PERIOD, THE NEXT FRONTAL SYSTEM TO REACH THE WEST COAST WILL
BRING A 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. AS THE SUPPORTING DYNAMICS EXTEND BEYOND THE ROCKIES,
THE SOUTH MAY SEE A REBOUND IN RAINFALL BY SATURDAY AS A FRONT
LINGERING OVER THE GULF LIFTS BACK NORTHWARD AHEAD OF POSSIBLE
DEVELOPING LOW PRESSURE AND COLD FRONT. CURRENT CONFIDENCE REMAINS
LOW FOR THE AXIS AND AMOUNT SPECIFICS OF THE RAINFALL AND THE
SURFACE FRONTAL EVOLUTION. EXPECT ANOTHER FRONT TO SPREAD SOME
RAIN/MOUNTAIN SNOW INTO THE NORTHWEST AND NORTHERN ROCKIES NEXT
WEEKEND.
THE WEDNESDAY-SUNDAY PATTERN WILL FAVOR PERSISTENTLY COOL DAYTIME
HIGHS OVER THE SOUTHERN THREE-FOURTHS OF THE WEST AND AT TIMES
INTO THE CENTRAL-SOUTHERN HIGH PLAINS, WITH MOST LOCATIONS 5-15F
OR SO BELOW NORMAL. FRIDAY-SATURDAY MAY BE THE COOLEST DAYS DURING
THE PERIOD UNDERNEATH THE UPPER TROUGH/LOW. ON THE OTHER HAND, THE
EASTERN U.S. AND NORTHERN TIER SHOULD BE ABOVE NORMAL, WITH
ANOMALIES AS HIGH AS PLUS 20-30F FOR LOWS OVER PARTS OF THE SOUTH
AND EAST ON WEDNESDAY-THURSDAY AHEAD OF THE PLAINS/MIDWEST SYSTEM.
FRONTAL PASSAGE WILL BRING A COOLER TREND TO THE EAST FRIDAY INTO
THE WEEKEND BUT WITH TEMPERATURES REMAINING ABOVE NORMAL IN MOST
CASES. MOST OF ANY DAILY RECORDS SHOULD BE FOR WARM LOWS, AT LEAST
IF SUCH READINGS CAN HOLD ON THROUGH THE END OF THE CALENDAR DAY.
TATE/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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