246
FXUS02 KWBC 160738
PMDEPD
EXTENDED FORECAST DISCUSSION...AMENDED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EST FRI DEC 16 2022
VALID 12Z MON DEC 19 2022 - 12Z FRI DEC 23 2022
***BITTERLY COLD TEMPERATURES LIKELY TO SETTLE OVER THE NORTHERN
PLAINS FOR MUCH OF NEXT WEEK***
***POTENTIAL FOR EAST COAST WINTER STORM TO DEVELOP LATE IN THE
WEEK***
..SYNOPTIC OVERVIEW
A SIGNIFICANT PATTERN CHANGE IS EXPECTED TO EVOLVED ACROSS MUCH OF
THE CONTINENTAL U.S. NEXT WEEK AS A PRONOUNCED UPPER TROUGH BUILDS
IN ACROSS THE EASTERN HALF OF THE NATION, ACCOMPANIED BY AN
IMPRESSIVE ARCTIC AIRMASS SETTLING SOUTHWARD ACROSS THE PLAINS AND
THEN ADVECTING EASTWARD, WITH WIDESPREAD SUBZERO TEMPERATURES
LIKELY FOR THE NORTH-CENTRAL STATES. THIS IS MAINLY IN RESPONSE
TO A BUILDING WEST COAST UPPER RIDGE (+PNA PATTERN) AND A NEGATIVE
ARCTIC OSCILLATION (-AO PATTERN) THAT ALLOWS ARCTIC AIRMASSES TO
DROP SOUTHWARD FROM CANADA. THINGS GET INTERESTING TOWARDS THE
END OF THE WEEK AS A POTENTIAL EAST COAST STORM DEVELOPS, AND THE
DETAILS OF THIS WILL BE DEPENDENT UPON THE PHASING OF BOTH
SOUTHERN AND NORTHERN STREAM SHORTWAVE ENERGY, AND WHEN THIS TAKES
PLACE. IF THE LOW DEVELOPS CLOSE ENOUGH TO THE COAST, IMPACTFUL
RAIN AND SNOW COULD MATERIALIZE FROM THE MID-ATLANTIC TO NEW
ENGLAND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE HAS A GOOD OVERALL DEPICTION OF THE
WEATHER PATTERN ON MONDAY, WITH THE MAIN DIFFERENCES OBSERVED WITH
THE TIMING OF THE UPPER TROUGH/CLOSED LOW ACROSS SOUTHWESTERN
CANADA AND ITS ARRIVAL OVER THE FAR NORTHERN PLAINS. BY TUESDAY,
THE SOUTHERN STREAM TROUGH OVER TEXAS IS MORE AMPLIFIED WITH THE
GFS AND SLIGHTLY FASTER WITH THE ECMWF, AND THE GFS REMAINS
SLIGHTLY MORE AMPLIFIED GOING THROUGH WEDNESDAY. GOING INTO
WEDNESDAY NIGHT, THE SECOND LOBE FROM A PORTION OF THE POLAR
VORTEX STARTS DROPPING SOUTH ACROSS THE UPPER MIDWEST, AND THE
AXIS OF THE TROUGH IS FARTHER EAST WITH THE CMC AND ECMWF, WHEREAS
THE GFS IS SHARPER AND SLOWER. THIS WILL HAVE IMPLICATIONS ON THE
EVENTUAL DEVELOPMENT OF THE COASTAL LOW NEAR THE EAST COAST, WITH
THE GFS HAVING A MORE OFFSHORE TRACK.
THE WPC FRONTS/PRESSURES WAS PRIMARILY BASED ON A 40% ECMWF/20%
GFS/20% CMC/20% ECENS BLEND FOR MONDAY AND TUESDAY, AND THEN THE
PROPORTION OF THE ECENS AND GEFS MEANS WERE INCREASED GOING
THROUGH THE REMAINDER OF THE WEEK TO ACCOUNT FOR THE INCREASING
MODEL UNCERTAINTY. FUTURE FORECAST UPDATES WILL PROVIDE
ADDITIONAL CLARITY ON THE EVENTUAL EAST COAST STORM EVOLUTION AND
POTENTIAL IMPACTS.
..WEATHER/HAZARD HIGHLIGHTS
THE MAIN WEATHER STORY THAT WILL MAKE WEATHER HEADLINES NEXT WEEK
WILL BE THE MASSIVE EXPANSE OF FRIGID TEMPERATURES FROM
MONTANA/NORTHERN PLAINS TO THE MIDWEST AND EVEN THE OHIO VALLEY.
A COUPLE OF REINFORCING COLD FRONTS WILL USHER IN THE COLDEST AIR
OF THE SEASON BY A CONSIDERABLE MARGIN WITH THE EXPECTATION OF
WIDESPREAD SUBZERO READINGS FOR OVERNIGHT LOWS FROM THE NORTHERN
ROCKIES TO THE CENTRAL/NORTHERN PLAINS AND THE UPPER MIDWEST, WITH
SOME LOWS APPROACHING -30 DEGREES ACROSS PORTIONS OF MONTANA AND
NORTH DAKOTA! ALTHOUGH THE FRIGID AIRMASS WILL MODIFY AS IT
REACHES THE OHIO VALLEY AND MID-SOUTH, IT WILL STILL BE QUITE COLD
WITH WIDESPREAD 0S AND 10S FOR OVERNIGHT LOWS BY THE END OF THE
WEEK, AND THIS VERY COLD WEATHER IS EXPECTED TO HAVE SOME STAYING
POWER AS THE CLIMATE PREDICTION CENTER OUTLOOK INDICATES HIGH
PROBABILITIES OF BELOW AVERAGE TEMPERATURES BEYOND THIS FORECAST
PERIOD.
THE POTENTIAL FOR AN EAST COAST WINTER STORM LATE IN THE FORECAST
PERIOD ALSO BEARS CLOSE MONITORING. THE OVERALL UPPER LEVEL
PATTERN IS GENERALLY SUPPORTIVE OF A WINTER STORM DEVELOPING IN
THIS REGION, ALTHOUGH MODEL DIFFERENCES AND RUN-TO-RUN VARIABILITY
LIMIT CONFIDENCE ON THE EXPECTED PLACEMENT OF HEAVIEST SNOW. A
LOW TRACK JUST OFF THE COAST WOULD FAVOR SIGNIFICANT SNOWFALL FOR
THE INTERSTATE 95 CORRIDOR, WHEREAS A TRACK ALONG THE COAST OR
JUST INLAND WOULD LIKELY INVOLVE A WINTRY MIX TO RAIN SCENARIO FOR
THOSE SAME GENERAL AREAS AND SNOW FARTHER INLAND.
ELSEWHERE, A SHORTWAVE TRACKING NEAR THE GULF COAST ALONG WITH AN
ASSOCIATED FRONTAL WAVE OVER THE NORTHERN GULF OF MEXICO COULD
PRODUCE A PERIOD OF ENHANCED RAINFALL ACROSS PORTIONS OF SOUTHERN
TEXAS AND LOUISIANA ON MONDAY, AND THEN INTO FLORIDA ON TUESDAY.
THE NORTHWEST SHOULD SEE MULTIPLE EPISODES OF RAIN AND HIGHER
ELEVATION SNOW WITH HIGHEST TOTALS OVER FAVORED TERRAIN.
CONFIDENCE IS MODERATE AT BEST FOR DAY-TO-DAY DETAILS REGARDING
AMOUNTS AND COVERAGE BUT THERE IS A GENERAL SIGNAL THAT TOTALS
SHOULD INCREASE TOWARD WEDNESDAY-THURSDAY.
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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