151
FXUS02 KWBC 261900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST THU JAN 26 2023
VALID 12Z SUN JAN 29 2023 - 12Z THU FEB 02 2023
...COLDEST WEATHER SO FAR THIS MONTH EXPECTED ACROSS THE DAKOTAS
AND THE UPPER MIDWEST STARTING THIS WEEKEND WITH DANGEROUSLY COLD
WIND CHILLS EXPECTED...
..OVERVIEW
LATEST GUIDANCE CONTINUES TO SHOW AN UPPER PATTERN DOMINATED BY
MEAN TROUGHING FROM A CLOSED LOW NEAR NORTHWESTERN HUDSON BAY
SOUTHWESTWARD THROUGH THE WESTERN U.S., WHILE AN UPSTREAM RIDGE
OVER THE EASTERN PACIFIC EVENTUALLY MIGRATES OVER OR JUST INLAND
OF THE WEST COAST. THIS PATTERN WILL SUPPORT A BROAD AREA OF WELL
BELOW NORMAL TEMPERATURES OVER THE WESTERN/CENTRAL U.S. WITH THE
COLDEST ANOMALIES OVER PARTS OF THE ROCKIES/HIGH PLAINS. AT THE
SAME TIME AN UPPER RIDGE MEANDERING OVER CUBA AND THE BAHAMAS WILL
TEND TO KEEP THE SOUTHEAST ON THE WARM SIDE RELATIVE TO NORMAL.
BETWEEN THESE TWO TEMPERATURE REGIMES, SHORTWAVE ENERGY AND THE
COMBINATION OF A COUPLE WAVY FRONTS ALONG WITH PERIODS OF GULF
INFLOW SHOULD SUPPORT A COUPLE OF SIGNIFICANT PRECIPITATION EVENTS
EAST OF THE ROCKIES WITH RAINFALL TO THE SOUTH/SOUTHEAST AND SOME
WINTRY WEATHER IN THE COLDER AIR. AN UPPER LOW/TROUGH DIGGING
INTO THE WESTERN U.S. MEAN TROUGH WILL ALSO SUPPORT SOME LOCALLY
ENHANCED RAIN AND HIGHER ELEVATION SNOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
IN CONTRAST TO 24 HOURS AGO WHEN THE GFS WAS IN THE MINORITY FOR
ITS DEPICTION OF A MORE AMPLIFIED WEST COAST TROUGH/EMBEDDED UPPER
LOW, THE 00Z/06Z GUIDANCE MADE A NOTABLE SHIFT IN THAT DIRECTION
WITH A FAIR AMOUNT OF FOLLOW-THROUGH IN THE 12Z CYCLE.
REPRESENTATIVE OF SOME OF THE SPREAD/VARIABILITY IN RECENT DAYS,
THE 00Z GFS HAD SWITCHED BACK TO A MORE OPEN/PROGRESSIVE FEATURE
BUT THE 06Z/12Z RUNS RETURNED TO A SLOWER AND MORE CLOSED
EVOLUTION (THOUGH A BIT FASTER THAN THE 00Z ECMWF AND 00Z/12Z CMC
BY DAY 7 THURSDAY). ENSEMBLE MEMBERS ARE STILL QUITE VARIED AND
NOT SURPRISINGLY YIELD AN OPEN TROUGH IN THEIR RESPECTIVE MEANS,
WHILE THE 12Z UKMET MADE A SIGNIFICANT CHANGE TO A MORE OPEN
FEATURE WITH NORTHERN STREAM PHASING VERSUS ITS 00Z RUN. OVERALL
PREFERENCE WAS TO INCORPORATE 00Z/06Z MAJORITY TRENDS EARLY-MID
PERIOD WHILE KEEPING SOME ENSEMBLE MEAN INFLUENCE LATER GIVEN THE
ONGOING UNCERTAINTY.
BEHIND THIS SYSTEM, THERE IS STILL A FAIR AMOUNT OF VARIABILITY
FOR HOW PACIFIC ENERGY MAY INTRUDE UPON THE MEAN RIDGE EXPECTED TO
REACH THE WEST COAST AROUND MIDWEEK. THE 00Z GFS CONSIDERABLY
FLATTENED THE RIDGE BUT MOST OTHER MODELS/MEANS HAVE HELD ONTO A
STRONGER RIDGE TO VARYING DEGREES. THE 06Z GFS WAS CLOSEST TO
CONSENSUS IN PRINCIPLE WHILE THE 12Z GFS HAS TRENDED TOWARD MORE
SOUTHEASTWARD AMPLITUDE FOR THE UPPER TROUGH APPROACHING BY DAY 7
THURSDAY.
ONE OTHER FORECAST PROBLEM INVOLVES THE SURFACE EVOLUTION OVER THE
EAST TOWARD MIDWEEK. TRENDS OVER THE PAST DAY HAVE BEEN FOR A
MORE SUPPRESSED WAVY FRONT, BUT THERE ARE STILL EXTREMES ON EITHER
SIDE OF THAT TREND. THE NEW 12Z UKMET IS REPRESENTATIVE OF A
SOLUTION CLOSER TO CONSENSUS FROM 24 HOURS AGO WHILE THE QUICK
PASSAGE OF A MORE AMPLIFIED THAN CONSENSUS NORTHERN STREAM
SHORTWAVE ACROSS THE EAST IN THE 06Z/12Z GFS LEADS TO MUCH
STRONGER HIGH PRESSURE OVER THE EAST NEXT WEDNESDAY. THE
ECMWF/CMC AND THE THREE ENSEMBLE MEANS REPRESENT THE MAJORITY
CLUSTER FOR THIS ASPECT OF THE FORECAST.
..WEATHER/HAZARD HIGHLIGHTS
AN ARCTIC SURGE BEHIND A STRONG COLD FRONT WILL BE MAKING WEATHER
HEADLINES ACROSS MUCH OF THE NORTH-CENTRAL U.S. AND NORTHERN
ROCKIES FROM THIS WEEKEND INTO THE MIDDLE OF NEXT WEEK. EXPECT
MUCH BELOW NORMAL TEMPERATURES ACROSS THE CENTRAL/NORTHERN PLAINS
TO INTERIOR PORTIONS OF THE NORTHWEST FOR THE WEEKEND INTO EARLY
NEXT WEEK, WITH HIGHS RUNNING UP TO 25-40F BELOW NORMAL FROM THE
CENTRAL HIGH PLAINS INTO PARTS OF MONTANA. THIS WOULD BE THE
COLDEST WEATHER SINCE CHRISTMAS FOR THIS REGION, WITH LOCATIONS
FROM EASTERN MONTANA TO NORTHERN MINNESOTA LIKELY REMAINING BELOW
ZERO FOR HIGHS AT LEAST ON SUNDAY-MONDAY. WIND CHILLS COULD REACH
40 BELOW AT TIMES FOR THESE AREAS. HIGHS IN THE 0 TO 10 DEGREE
RANGE MAY EXTEND AS FAR SOUTH AS NORTHEAST COLORADO AND NORTHERN
KANSAS. THE REMAINDER OF THE INTERIOR WEST WILL ALSO BE QUITE
COLD, WITH MONDAY-TUESDAY BEING THE DAYS LIKELY TO HAVE THE
GREATEST COVERAGE HIGHS 15-25F BELOW NORMAL WITH GRADUAL
MODERATION THEREAFTER.
WHILE SOME UNCERTAINTY REMAINS WITH THE EVOLUTION OF THE
UPPER-LEVEL PATTERN OVER THE WESTERN U.S., THE TROUGH EXPECTED TO
DROP SOUTHWARD AND ASSOCIATED SURFACE REFLECTION SHOULD PRODUCE A
PERIOD OF RAIN AND HIGHER ELEVATION SNOW ACROSS SOUTHERN
CALIFORNIA AND THE SOUTHWEST/SOUTHERN GREAT BASIN WITH SOME
LOCALIZED ENHANCEMENT POSSIBLE WITHIN A BROADER AREA OF MODERATE
TOTALS. SHORTWAVE ENERGY INITIALLY EJECTING FROM THE SOUTHWESTERN
U.S. WILL LIKELY SUPPORT ONE OR MORE SURFACE WAVES OF LOW PRESSURE
FROM THE SOUTHERN PLAINS/GULF COAST INTO THE EASTERN U.S. DURING
THE WEEKEND INTO EARLY NEXT WEEK. GULF MOISTURE RETURN MAY
SUPPORT A CORRIDOR OF MODERATE TO HEAVY RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST STATES AND SOUTHEAST ON SUNDAY, WITH MORE
MODEST RAINS SPREADING NORTHWARD OVER THE EAST-CENTRAL U.S.
INTO/AHEAD OF A WAVY FRONT. THE DAY 4 (12Z SUNDAY-12Z MONDAY)
EXCESSIVE RAINFALL OUTLOOK MAINTAINS A SLIGHT RISK AREA ACROSS
PARTS OF THIS REGION WITH THIS AFTERNOON'S UPDATE EXTENDING THE
SLGT AREA INTO PARTS OF GEORGIA AND THE SOUTHERN TIP OF SOUTH
CAROLINA BASED ON GUIDANCE CONSENSUS FOR A BAND OF HEAVY RAINFALL
WHERE THE GROUND IS WET FROM RECENT RAINFALL. MORE WAVINESS NEAR
THE CENTRAL GULF COAST AND THE UPPER SYSTEM EMERGING FROM THE
SOUTHWEST WILL LIKELY INCREASE PRECIPITATION ACROSS THE SOUTHERN
TIER AGAIN DURING THE LATTER HALF OF THE PERIOD. WINTER WEATHER
WILL BE POSSIBLE TO THE NORTH/NORTHWEST OF THE RAIN AREA, WITH
LOCATIONS FROM THE MIDWEST INTO NEW ENGLAND GENERALLY IN THE MOST
FAVORED AXIS FOR SOME GENERALLY LIGHT SNOWFALL. SUFFICIENT
PERSISTENCE OF COLD AIR BY LATE IN THE PERIOD COULD INCREASE THE
POSSIBILITY FOR A TRANSITION ZONE OF FREEZING RAIN/SLEET BETWEEN
THE RAIN AND SNOW AREAS BUT ANY SPECIFICS HAVE LOW CONFIDENCE AT
THIS TIME. THE FORECAST OVER THE SOUTHERN PART OF THE PLAINS WILL
DEPEND ON THE UNCERTAIN SPECIFICS OF THE SOUTHWEST UPPER
TROUGH/LOW WITH SOME SIGNIFICANT RAIN AND/OR SNOW POSSIBLE
DEPENDING ON THE FEATURE'S EVOLUTION/TRACK.
RAUSCH/HAMRICK
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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