246
FXUS02 KWBC 240658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM 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 12Z MODEL GUIDANCE SUITE AGREES VERY WELL ON THE MAIN PATTERN
EVOLUTION GOING THROUGH FRIDAY AND SATURDAY. GOING AHEAD INTO
SUNDAY, A TROUGH SETTLING SOUTHWARD FROM BRITISH COLUMBIA WILL
INTRODUCE MORE UNCERTAINTIES ACROSS THE WEST COAST REGION AND THIS
WOULD HAVE AN EFFECT ON THE DEGREE OF SURFACE LOW DEVELOPMENT OVER
CALIFORNIA GOING INTO THE BEGINNING OF NEXT WEEK. THE GFS HAS
TRENDED MORE IN THE DIRECTION OF THE ECMWF/CMC/UKMET IN TERMS OF
AMPLITUDE AND WESTWARD EXTENSION OF THE WEST COAST TROUGH, BUT IS
ON THE SLOWER SIDE OF THE GUIDANCE. THE UKMET IS ON THE FASTER
SIDE OF THE GUIDANCE, SO A CMC/ECMWF BLEND WORKS WELL FOR A
STARTING POINT IN THE FORECAST HERE. LOOKING AHEAD TO
MONDAY/TUESDAY, MODELS ARE IN CLOSEST AGREEMENT ACROSS THE EASTERN
U.S. AND THE UPPER RIDGE OVER THE BAHAMAS/CUBA, AND MORE SPREAD
ACROSS THE WEST AND THE NORTHERN TIER STATES. THE CMC REMAINS
MORE PRONOUNCED WITH THE TROUGH ACROSS THE WEST COAST WHEREAS THE
GFS/ECMWF ARE WEAKER AND MORE INLAND. THE FRONTS/PRESSURES
FORECAST WAS PRIMARILY BASED ON A MULTI-DETERMINISTIC BLEND
THROUGH SATURDAY, AND THEN LESS OF THE 18Z GFS (IT HAD A WEAKER
WESTERN TROUGH) AND MORE OF THE ENSEMBLE MEANS GOING INTO THE
SUNDAY TO TUESDAY TIME PERIOD.
..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 AND NORTHERN NEW ENGLAND SATURDAY. 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 ACROSS PORTIONS OF MONTANA, THE DAKOTAS, AND NEBRASKA.
THIS WOULD BE THE COLDEST WEATHER SINCE CHRISTMAS FOR THIS REGION,
WITH SOME LOCATIONS 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.
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, WITH MORE MODEST RAINS
SPREADING NORTHWARD OVER THE EAST-CENTRAL U.S. INTO/AHEAD OF A
WAVY FRONT. IN THIS PATTERN, THE PRE-FRONTAL AIRMASS WARMS AS
UPPER RIDGING BUILDS FROM THE SOUTHEAST.
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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