796
FXUS02 KWBC 250659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST WED JAN 25 2023
VALID 12Z SAT JAN 28 2023 - 12Z WED FEB 1 2023
***COLDEST WEATHER SO FAR THIS MONTH EXPECTED ACROSS THE DAKOTAS
AND THE UPPER MIDWEST STARTING THIS WEEKEND***
..SYNOPTIC OVERVIEW
A BROAD UPPER TROUGH WITH CYCLONIC FLOW ALOFT WILL ENCOMPASS MUCH
OF THE NORTHERN HALF OF THE U.S. GOING INTO THE WEEKEND AND INTO
MONDAY, AND QUASI-ZONAL FLOW ALOFT OVER THE SOUTHERN STATES. AT
THE SURFACE, A STRONG COLD FRONT WILL HERALD THE ARRIVAL OF AN
ARCTIC AIRMASS WITH WELL BELOW AVERAGE TEMPERATURES FROM THE
CENTRAL/NORTHERN ROCKIES EASTWARD TO THE UPPER MIDWEST IN TIME FOR
THE WEEKEND. THE STRONG COLD FRONT IS FORECAST TO SPUR SURFACE
CYCLOGENESIS ACROSS THE SOUTHERN PLAINS BY THE WEEKEND, BUT IT
CURRENTLY APPEARS THIS LOW SHOULD BE WEAKER THAN THE STORM SYSTEM
THAT IS CURRENTLY ONGOING. HOWEVER, THERE WILL STILL BE ENOUGH
MOISTURE RETURN FROM THE GULF TO PRODUCE AREAS OF HEAVY RAIN AND
THUNDERSTORMS ACROSS THE DEEP SOUTH. 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 AND WARM TEMPERATURES ACROSS FLORIDA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
ABOVE AVERAGE 00Z MODEL AGREEMENT EXISTS ACROSS THE CONTINENTAL
U.S. FOR THE UPCOMING WEEKEND WITH BROAD CYCLONIC FLOW ALOFT
ACROSS MUCH OF SOUTHERN CANADA AND THE NORTH-CENTRAL STATES.
SHORTWAVE ENERGY DROPPING SOUTH ALONG THE WEST COAST IS GETTING
BETTER REFINED BY THE LATEST GUIDANCE, WITH A TREND TOWARDS A
STRONGER SYSTEM THAT WILL BRING THE NEXT ROUND OF PRECIPITATION TO
CALIFORNIA AND NEIGHBORING STATES. AT THE TIME OF
FRONTS/PRESSURES ISSUANCE, THE GFS AND UKMET WERE SLOWER IN THE
ARRIVAL OF THE TROUGH AXIS COMPARED TO THE FASTER ECMWF AND CMC.
UPON EXAMINATION OF THE ENSEMBLE GUIDANCE AND THE ICON AND JMA
MODELS, THERE WAS BROADER SUPPORT FOR THE SLOWER SIDE OF THE MODEL
GUIDANCE, SO THE FORECAST DAYS 3 THROUGH 5 WERE HEDGED SLIGHTLY
MORE TOWARD THE 18Z GFS/12Z UKMET SOLUTIONS. SOME GEFS AND ECENS
WERE ADDED TO THE MIX GOING INTO THE MONDAY TO WEDNESDAY TIME
PERIOD TO ACCOUNT FOR NORMAL LEVELS OF MESOSCALE DIFFERENCES.
..WEATHER/HAZARD HIGHLIGHTS
IN THE WAKE OF THE DEPARTING ALBERTA CLIPPER LOW, 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 20 TO 35 DEGREES BELOW NORMAL, AND THINGS HAVE
TRENDED EVEN COLDER WITH THE LATEST FORECAST ISSUANCE. 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 SATURDAY THROUGH MONDAY, AND
PERHAPS INTO TUESDAY. 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 SOME
UNCERTAINTY REMAINS WITH THE EVOLUTION OF THE UPPER-LEVEL PATTERN
OVER THE WESTERN U.S., RAIN AND MOUNTAIN SNOW PROSPECTS SHOULD
GENERALLY INCREASE WITH TIME IN CALIFORNIA AND THE SOUTHWEST AS
THE PACIFIC COLD FRONT DROPS SOUTHWARD, WITH AT LEAST SOME LIGHT
HIGHER ELEVATION/INTERIOR SNOWFALL AND RAIN FOR THE SOUTHERN
CALIFORNIA 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. THERE IS NOW ENOUGH MODEL
SUPPORT TO WARRANT THE ISSUANCE OF A DAY 5 SLIGHT RISK AREA FROM
SOUTHERN LOUISIANA TO THE FAR WESTERN FLORIDA PANHANDLE, WHERE
MULTIPLE ROUNDS OF HEAVY RAINFALL WILL BE POSSIBLE. ANOTHER WAVE
OVER THE CENTRAL GULF COAST WILL INCREASE RAIN CHANCES AGAIN LATER
IN THE PERIOD ON TUESDAY.
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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