522
FXUS02 KWBC 110701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST THU JAN 11 2024
VALID 12Z SUN JAN 14 2024 - 12Z THU JAN 18 2024
...AN ARCTIC AIRMASS BLANKETS MUCH OF THE NORTHERN AND CENTRAL
U.S. THROUGH EARLY NEXT WEEK...
..OVERVIEW
AN UPPER-LEVEL LOW WILL GET PRETTY WOUND UP NEAR JAMES BAY, CANADA
WHILE WAVES OF SHORTWAVE ENERGY ROTATE THROUGH ITS SOUTHERN
PERIPHERY (THE MIDWEST AND NORTHEAST U.S.). MEANWHILE, AN UPPER
RIDGE WILL DEVELOP AND AMPLIFY OVER THE EASTERN PACIFIC AND WEST
COAST. THIS UPPER PATTERN WILL RESULT IN ARCTIC HIGH PRESSURE AT
THE SURFACE FLOWING THROUGH THE NORTHERN ROCKIES/PLAINS AND INTO
MUCH OF THE CENTRAL U.S..
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE ENSEMBLE MEANS CAPTURE THE SYNOPTIC EVOLUTION OF THE UPPER
LEVEL PATTERN REASONABLY WELL IN THE MEDIUM RANGE. THE
DETERMINISTIC GUIDANCE STRUGGLES TO CONSISTENTLY CLUSTER AROUND
ANY ONE SOLUTION. A BLEND OF THE 12Z AND 18Z GFS AS WELL AS THE
00Z AND 12Z EC WERE USED ON DAY 3 SINCE THE 12Z UKMET/CMC
STRUGGLED TO PRESENT ANYTHING SIMILAR TO WHAT THE ENSEMBLE MEANS
AND EC/GFS HAD. ON DAY 4 THE 18Z GEFS AND 12Z ECE WERE INTRODUCED
TO THE BLEND TO MITIGATE SOME OF THE OVERAMPLIFICATION OF A
POSITIVELY TILTED TROUGH IN THE WEST BY THE 12Z EC. THE CANADIAN
IS INTRODUCED ON DAY 5 SINCE IT SORT OF CATCHES UP TO THE
EC/GFS/ENSEMBLE MEAN SOLUTION WITH RESPECT TO THE SHORTWAVE
PROPAGATING THROUGH THE MISSISSIPPI VALLEY. THE PREVIOUS EC/GFS
RUNS WERE REMOVED. THE CANADIAN ENSEMBLE MEAN IS INTRODUCED ON DAY
6 AND REPLACES THE DETERMINISTIC 12Z CMC. ON DAY 7, ONLY THE 3
ENSEMBLE MEANS WERE USED.
THE GFS CONSISTENTLY HAS A STRONGER MEAN LOW OVER JAMES BAY
THROUGHOUT THE MEDIUM RANGE PERIOD. IT IS ALSO MORE PROGRESSIVE
WITH ITS EMBEDDED SHORTWAVE ENERGY COMPARED TO THE EC ON DAY 5,
BUT THE CANADIAN IS THE DEEPEST AND MOST PROGRESSIVE OF THE
OPERATIONAL MODELS. THE UKMET HAS IT'S SHORTWAVE STILL MOVING
THROUGH THE INTERMOUNTAIN WEST ON DAY 5. THE OPERATIONAL EURO AND
GFS HAVE BOTH SLOWED DOWN CONSIDERABLY OVER THEIR LAST FEW RUNS
AND NOW HAS THE SHORTWAVE MOVING THROUGH THE EAST ON DAY 6, WHILE
THE 12Z CANADIAN HAS THAT SAME ENERGY OUT INTO THE WESTERN
ATLANTIC. THE ENSEMBLE MEANS, ESPECIALLY THE GEFS AND ECE, HAVE
RELATIVELY LOW SPREAD ACROSS THE LOWER 48 THROUGHOUT THE MEDIUM
RANGE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN WEATHER HIGHLIGHT DURING THE MEDIUM RANGE WILL BE THE
ARCTIC BLAST EXPECTED TO IMPACT THE NORTHERN ROCKIES, NORTHERN
GREAT BASIN, GREAT PLAINS, MISSISSIPPI VALLEY AND MIDWEST. THE
SYNOPTIC SETUP INCLUDING A STRENGTHENING UPPER RIDGE IN THE WEST
AND AN MASSIVE UPPER LOW IN THE EAST WILL SUPPORT THE DESCENT OF
HIGH PRESSURE THROUGH THE CENTRAL U.S. THIS WEEKEND THROUGH EARLY
NEXT WEEK. THE COLDEST PARTS OF THIS AIRMASS WILL BE OVER PARTS OF
NORTHERN MONTANA WHERE LOW TEMPERATURES COULD BOTTOM OUT NEAR 40
DEGREES BELOW ZERO SUNDAY MORNING. PARTS OF THE NORTHERN ROCKIES
DOWN THROUGH THE CENTRAL PLAINS AND MIDDLE MISSISSIPPI VALLEY WILL
STRUGGLE TO MAKE IT ABOVE ZERO DEGREES SATURDAY, SUNDAY AND MONDAY
NIGHTS. THIS WILL MAKE FOR VERY DANGEROUS OUTDOOR CONDITIONS.
MINIMUM TEMPERATURE ANOMALIES WILL BE BETWEEN 20-40 DEGREES BELOW
AVERAGE FOR THESE AREAS. FREEZING TEMPERATURES WILL ALSO MAKE
THEIR WAY TO THE GULF COAST MONDAY AND TUESDAY NIGHT. TEMPERATURES
WILL BEGIN TO REBOUND ON WEDNESDAY AS ANOTHER SHORTWAVE ENTERS THE
NORTHERN PLAINS/UPPER MIDWEST AND SHIFTS SURFACE WINDS OUT OF THE
SOUTH.
THE SHORTWAVE ENERGY RESPONSIBLE FOR SPREADING TROPICAL MOISTURE
OVER THE NORTHWEST LEADING TO THE PRODUCTION OF HEAVY SNOW WILL
SPREAD THAT MOISTURE AND SNOW INTO PARTS OF THE CENTRAL/SOUTHERN
ROCKIES AND INTERMOUNTAIN WEST ON SUNDAY. SNOW PROBABILITIES
REMAIN HIGH FOR THE WASATCH, UINTA, COLORADO ROCKIES, SAN JUAN AND
SANGRE DE CRISTO MOUNTAINS. A SWATH OF SNOW SHOWERS MAY ALSO
SPREAD INTO THE CENTRAL/SOUTHERN PLAINS AND MIDDLE MISSISSIPPI
VALLEY ON SUNDAY. SNOW WILL CONTINUE OVER THE COLORADO ROCKIES
INTO MONDAY WHILE SOME MORE SNOW SHOWERS DEVELOP OVER THE
TENNESSEE/OHIO VALLEYS. A COASTAL LOW IS EXPECTED TO DEVELOP JUST
OFF OF THE SOUTHEAST COAST LATER ON MONDAY AND GENERATE SHOWERS
AND THUNDERSTORMS ACROSS THE CENTRAL GULF COAST AND MUCH OF
FLORIDA THROUGH MIDWEEK. THE EXACT TRACK OF THIS SYSTEM HAS YET TO
BE IRONED OUT BUT THERE SEEMS TO BE SOME AGREEMENT BETWEEN THE
EURO AND GFS FOR SOME SNOW SHOWERS EXTENDING FROM THE MID-ATLANTIC
UP INTO THE NORTHEAST TUESDAY INTO WEDNESAY AFTERNOON.
KEBEDE
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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page