403
FXUS02 KWBC 241822
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
121 PM EST TUE JAN 24 2023
VALID 12Z FRI JAN 27 2023 - 12Z TUE JAN 31 2023
***COLDEST WEATHER SO FAR THIS MONTH EXPECTED ACROSS THE DAKOTAS
AND THE UPPER MIDWEST STARTING THIS WEEKEND***
..SYNOPTIC OVERVIEW
THE DEPARTURE OF THE STRONG LOW PRESSURE SYSTEM FROM NEW ENGLAND
LATE THURSDAY WILL YIELD AN UPPER LEVEL PATTERN WITH BROAD
CYCLONIC FLOW WITH AN ALBERTA CLIPPER SYSTEM TRACKING EASTWARD
ACROSS THE GREAT LAKES ON FRIDAY. THIS WILL HERALD THE ARRIVAL OF
AN ARCTIC AIRMASS SETTLING SOUTHWARD FROM CANADA. THE STRONG COLD
FRONT WILL LIKELY SPUR SURFACE CYCLOGENESIS ACROSS THE SOUTHERN
PLAINS BY THE WEEKEND, BUT IT CURRENTLY APPEARS THIS LOW SHOULD BE
WEAKER THAN THE ONE THAT WILL BE IN PLACE OVER THE NEXT COUPLE OF
DAYS. THE SOUTHEAST RIDGE IS EXPECTED TO REMAIN RATHER STRONG
OVER THE BAHAMAS/SOUTHWESTERN ATLANTIC, AND THIS WILL TEND TO
LIMIT THE SOUTHWARD EXTENT OF THE ARCTIC AIRMASS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00 UTC/06 UTC DETERMINISTIC MODEL GUIDANCE IS IN GOOD
AGREEMENT AT THE START OF THE MEDIUM RANGE PERIOD
(FRIDAY/SATURDAY) DEPICTING A HIGHLY AMPLIFIED PATTERN WITH MEAN
UPPER-LEVEL TROUGHING ANCHORED OVER THE CENTRAL/EASTERN CONUS AND
LARGE-SCALE RIDGING OVER THE NORTHEASTERN PACIFIC. SMALL SPREAD
BETWEEN THE INDIVIDUAL MEMBERS OF THE ENSEMBLE GUIDANCE FURTHER
SUPPORTS THIS AGREEMENT. LINGERING WAVES OF UPPER-LEVEL ENERGY
REMAINED EMBEDDED IN THE FLOW, ONE IN THE GREAT LAKES VICINITY
ASSOCIATED WITH A CLIPPER SYSTEM AT THE SURFACE AND ANOTHER OVER
THE SOUTHWEST. THE MODEL BLEND FOR THE WPC MEDIUM RANGE PRODUCT
SUITE BEGAN WITH AN EVEN BLEND OF THE DETERMINISTIC GUIDANCE,
SPLITTING THE GFS CONTRIBUTION UP BETWEEN THE 00 UTC/06 UTC RUNS.
THIS BLEND ALSO GENERALLY FOLLOWED CONTINUITY FROM THE PRIOR
FORECAST. MODEL DIFFERENCES RAPIDLY INCREASE BY SUNDAY WITH
DISAGREEMENT OVER THE EVOLUTION OF A TROUGH DEVELOPING UPSTREAM OF
THE PACIFIC NORTHWEST. PAST RUNS OF THE GFS ARE MORE OF AN OUTLIER
COMPARED TO THE OTHER GUIDANCE WITH A FLATTER TROUGH WHILE THE
RECENT 00 UTC/06 UTC RUNS CONVERGE TOWARDS A MORE SIMILAR
EVOLUTION, WITH THE CAVEAT THAT SIGNIFICANT TIMING/LOCATION
DIFFERENCES EXIST BETWEEN THE GUIDANCE AND SPREAD IN THE ENSEMBLES
RAPIDLY INCREASES. HOWEVER, AFTER SUNDAY, THE 00 UTC GFS TRENDED
AWAY FROM THE OTHER GUIDANCE BEFORE REVERSING COURSE BACK WITH THE
06 UTC RUN. THE INFLUENCE OF THE ENSEMBLES WAS INTRODUCED INTO THE
BLEND AS THE MEAN PATTERN WAS GENERALLY SIMILAR, INCLUDING THE 00
UTC GEFS MEAN, AND THE DETAILS WILL BE FURTHER RESOLVED WHEN THE
GUIDANCE CONVERGES TOWARDS A SIMILAR SOLUTION. THIS IS ESPECIALLY
TRUE FOR LATE IN THE PERIOD WHEN BLENDING ACROSS THE DETERMINISTIC
GUIDANCE WILL WASH OUT ANY SIGNIFICANT DETAILS GIVEN THE LACK OF
OVERLAP AMONGST THE MODEL SOLUTIONS. THE EVOLUTION OF THIS FEATURE
WILL BE IMPORTANT AS IT WILL HAVE AN IMPACT ON EVENTUAL
PRECIPITATION CHANCES IN THE WEST, ESPECIALLY IF THE FORECAST WERE
TO TREND MORE TOWARDS THE OUTLIER RUNS OF THE GFS WHICH ARE
GENERALLY SLOWER AND FURTHER NORTH WITH THE QPF THAN THE OTHER
GUIDANCE.
..WEATHER/HAZARD HIGHLIGHTS
IN THE WAKE OF THE DEPARTING NORTHEAST U.S. STORM, AN ALBERTA
CLIPPER LOW WILL PRODUCE MAINLY LIGHT SNOW ACROSS PORTIONS OF THE
GREAT LAKES REGION FRIDAY. THE SOUTHWARD PLUNGE OF A TRAILING
COLD FRONT WILL ADVECT AN ARCTIC SURFACE HIGH PRESSURE DOWN ACROSS
THE NORTH-CENTRAL U.S. AND THEN INTO THE NORTHERN ROCKIES/WESTERN
HIGH PLAINS. EXPECT MUCH BELOW NORMAL TEMPERATURES ACROSS THE
NORTH-CENTRAL U.S. FOR THE WEEKEND INTO EARLY NEXT WEEK, WITH
HIGHS RUNNING UP TO 15-25 DEGREES BELOW NORMAL. THIS WOULD BE THE
COLDEST WEATHER SINCE CHRISTMAS FOR THIS REGION, WITH SOME
LOCATIONS IN THE FAR NORTHERN PLAINS/UPPER MIDWEST REMAINING
SUBZERO FOR DAYTIME HIGHS BY SUNDAY. THIS COLD WEATHER WILL ALSO
BE EXPECTED TO REACH INTO THE NORTHWEST/NORTHERN INTERMOUNTAIN
WEST. UPPER TROUGH PASSAGE COMBINED WITH LOWER ATMOSPHERIC
UPSLOPE FLOW WILL PRODUCE MODERATE TO LOCALLY HEAVY TERRAIN
ENHANCED SNOWS DOWN ACROSS NORTH-CENTRAL PARTS OF THE
INTERMOUNTAIN WEST/NORTHERN ROCKIES/WESTERN HIGH PLAINS SATURDAY
AND SUNDAY. WHILE UNCERTAINTY REMAINS WITH THE EVOLUTION OF THE
UPPER-LEVEL PATTERN OVER THE WESTERN U.S., PRECIPITATION CHANCES
SHOULD GENERALLY INCREASE WITH TIME IN CALIFORNIA AND THE
SOUTHWEST AS THE TRAILING COLD FRONT EVENTUALLY PUSHES SOUTHWARD,
WITH AT LEAST SOME LIGHT HIGHER ELEVATION/INTERIOR SNOWFALL AND
RAIN FOR THE COAST AND DESERT SOUTHWEST.
THE SHORTWAVE ENERGY INITIALLY FROM THE SOUTHWESTERN U.S. IS
EXPECTED TO EJECT EASTWARD ACROSS THE PLAINS AND SUPPORT A NEW LOW
PRESSURE SYSTEM OVER THE WEEKEND INTO EARLY NEXT WEEK OVER TEXAS
AND THE CENTRAL GULF COAST REGION. GULF MOISTURE RETURN MAY
SUPPORT A CORRIDOR OF MODERATE TO HEAVY RAINFALL OVER PORTIONS OF
THE CENTRAL GULF COAST STATES AND VICINITY SATURDAY AND SUNDAY,
WITH MORE MODEST RAINS SPREADING NORTHWARD OVER THE EAST-CENTRAL
U.S. INTO/AHEAD OF A WAVY FRONT. ANOTHER WAVE OVER THE CENTRAL
GULF COAST WILL INCREASE RAIN CHANCES AGAIN LATER IN THE PERIOD ON
TUESDAY. IN THIS PATTERN, THE PRE-FRONTAL AIRMASS WARMS AS UPPER
RIDGING BUILDS FROM THE SOUTHEAST.
PUTNAM/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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