911
FXUS21 KWNC 291941
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 29 2023
SYNOPSIS: A SERIES OF MID-LEVEL LOWS ARE PREDICTED TO TRACK ACROSS THE
CONTIGUOUS U.S. (CONUS) BRINGING A PERIOD OF ACTIVE WEATHER TO MUCH OF THE
COUNTRY. MULTIPLE STORMS ARE EXPECTED TO IMPACT THE COUNTRY, RESULTING IN
MULTIPLE RISK AREAS HIGHLIGHTED ACROSS THE CONUS FOR EPISODES OF HEAVY
PRECIPITATION, HEAVY SNOW, AND HIGH WINDS. DESPITE A NEGATIVE ARCTIC
OSCILLATION (AO) DURING THE NEXT TWO WEEKS, IT REMAINS UNCLEAR IF AND WHEN A
SIGNIFICANT ARCTIC AIR OUTBREAK WILL OCCUR.
HAZARDS
MODERATE RISK OF PERIODS OF HEAVY PRECIPITATION FOR PARTS OF THE SOUTHEAST AND
EAST COAST, SAT-WED, JAN 6-10.
MODERATE RISK FOR HEAVY SNOW FOR THE KLAMATH AND SIERRA NEVADA MOUNTAINS, SAT,
JAN 6.
MODERATE RISK OF HIGH WINDS FOR PORTIONS OF THE INTERIOR WEST, SAT-MON, JAN 6-8.
SLIGHT RISK FOR HEAVY SNOW FOR THE KLAMATH, SIERRA NEVADA MOUNTAINS, AND
COASTAL RANGES OF NORTHERN CALIFORNIA, SAT, JAN 6.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR THE CASCADES, SAT-FRI, JAN 6-12.
SLIGHT RISK OF HEAVY PRECIPITATION FOR NORTHERN CALIFORNIA AND THE PACIFIC
NORTHWEST, SAT, JAN 6.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF THE INTERIOR WEST,
SAT-MON, JAN 6-8.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR PARTS OF THE CENTRAL AND SOUTHERN
PLAINS, UPPER AND MIDDLE MISSISSIPPI VALLEY, GREAT LAKES, AND OHIO VALLEY,
SAT-WED, JAN 6-10.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FOR PARTS OF THE SOUTHEASTERN
CONUS AND EAST COAST, SAT-FRI, JAN 6-12.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR THE SOUTHERN TO CENTRAL APPALACHIANS
AND PARTS OF THE NORTHEAST, SAT-FRI, JAN 6-12.
SLIGHT RISK OF EPISODES OF HIGH WINDS FOR PARTS OF THE EAST COAST, SAT-FRI, JAN
6-12.
SLIGHT RISK OF HIGH WINDS FOR THE WEST AND CENTRAL AND SOUTHERN HIGH PLAINS,
SAT-MON, JAN 6-8.
SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA, AND COASTAL
SOUTHWESTERN ALASKA, FRI-THU, SAT-WED, JAN 6-10.
DETAILED SUMMARY
FOR MONDAY JANUARY 01 - FRIDAY JANUARY 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JANUARY 06 - FRIDAY JANUARY 12: THERE IS GOOD MULTI-MODEL
AGREEMENT INDICATING AMPLIFIED MID-LEVEL TROUGHING OVER THE WEST COAST AT THE
BEGINNING OF WEEK-2 TRACKING ACROSS THE CONUS THEREAFTER. THE GREATEST CHANCES
FOR HEAVY PRECIPITATION ACROSS THE WEST COAST IS ON DAY 8 (JAN 6), WITH THE
ECMWF AND GEFS INTEGRATED VAPOR TRANSPORT (IVT) TOOL SHOWING ENHANCED VALUES AT
THE ONSET OF WEEK-2, QUICKLY DECREASING AFTERWARD. A MODERATE RISK (>40%
CHANCE) OF HEAVY SNOW IS CONTINUED FOR THE KLAMATH AND SIERRA NEVADA MOUNTAINS,
JAN 6, WITH A SLIGHT RISK FOR THE KLAMATH, SIERRA NEVADA MOUNTAINS, AND COASTAL
RANGES OF NORTHERN CALIFORNIA. A SLIGHT RISK OF HEAVY SNOW IS POSTED FOR THE
CASCADES, JAN 6-8 ASSOCIATED WITH A COLD FRONT EXTENDING FROM WESTERN CANADA
INTO THE PACIFIC NORTHWEST. SLIGHT RISKS (>20% CHANCE) FOR HEAVY SNOW ARE ALSO
DESIGNATED FOR THE HIGHER ELEVATIONS OF THE INTERIOR WEST, JAN 6-8, WHERE THE
GEFS SNOW WATER EQUIVALENT (SWE) PROBABILISTIC EXTREMES TOOL (PET) SHOWS AT
LEAST A 20% CHANCE OF 3-DAY TOTALS EXCEEDING THE 85TH PERCENTILE
CLIMATOLOGICALLY AND HALF AN INCH (ONE INCH LOCALLY). A BROAD AREA IS
HIGHLIGHTED ACROSS THE WEST AND THE CENTRAL AND SOUTHERN PLAINS, JAN 6-8, WHERE
PETS INDICATE AT LEAST A 20% CHANCE OF EXCEEDING THE 85TH PERCENTILE WITH WINDS
EXCEEDING 20 MPH. AN EMBEDDED MODERATE RISK OF HIGH WINDS IS DESIGNATED FOR THE
INTERIOR WEST WHERE THE PETS SHOW AT LEAST A 30% CHANCE OF EXCEEDING THESE
THRESHOLDS.
MID-LEVEL TROUGHING IS PREDICTED OVER THE SOUTH-CENTRAL CONUS AT THE BEGINNING
OF THE PERIOD, SUPPORTING SURFACE LOW FORMATION OVER THE SOUTHEASTERN CONUS
WHICH COULD BRING HEAVY PRECIPITATION AND HIGH WINDS TO THIS REGION AND THE
EAST COAST. AS THIS SURFACE LOW MOVES OFF THE EAST COAST, THE AFOREMENTIONED
TROUGH OVER THE WEST IS PREDICTED TO PROPAGATE ACROSS THE CENTRAL CONUS,
RESULTING IN SURFACE LOWS OVER THE SOUTH-CENTRAL CONUS AND THE BORDER OF CANADA
AND THE NORTHERN PLAINS. THESE STORMS AND ASSOCIATED FRONTS SUPPORT A SLIGHT
RISK OF PERIODS OF HEAVY SNOW FOR PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
UPPER AND MIDDLE MISSISSIPPI VALLEY, GREAT LAKES, AND OHIO VALLEY, JAN 6-10. A
BROAD TEMPORAL AND SPATIAL RANGE IS HIGHLIGHTED DUE TO THE UNCERTAINTY
REGARDING STORM DETAILS AND ASSOCIATED IMPACTS. THE POTENTIAL FOR HIGH WINDS
AND SNOW INCREASES THE CHANCES FOR BLIZZARD CONDITIONS.
AS THIS STORM TRACKS EASTWARD, WET AND WINDY CONDITIONS ARE POSSIBLE ACROSS THE
EAST. A BROAD AREA IS HIGHLIGHTED FOR A SLIGHT RISK OF ROUNDS OF HEAVY
PRECIPITATION FOR THE SOUTHEASTERN CONUS AND EAST COAST AS WELL AS A SLIGHT
RISK OF PERIODS OF HEAVY SNOW ACROSS THE SOUTHERN TO CENTRAL APPALACHIANS AND
PARTS OF THE NORTHEAST. THE ENTIRETY OF WEEK-2 IS DESIGNATED FOR THESE HAZARDS
SINCE THE FRONT COULD LINGER WHILE EXTENDING FROM THIS SURFACE LOW AS IT TRACKS
TOWARDS THE NORTHEAST, IN ADDITION TO POSSIBLE RELOADING OF THE MID-LEVEL
TROUGH ACROSS THE CENTRAL CONUS AT THE END OF THE PERIOD. A MODERATE RISK OF
HEAVY PRECIPITATION IS DESIGNATED FOR PARTS OF THE SOUTHEAST AND EAST COAST,
JAN 6-10, BASED ON THE ECMWF PET INDICATING AT LEAST A 30% CHANCE OF 3-DAY
LIQUID EQUIVALENT EXCEEDING THE 85TH PERCENTILE (>40% ACROSS THE NORTHEAST AND
SOUTHEAST) AND UNCALIBRATED GUIDANCE SHOWING AT LEAST HALF AN INCH IN A 24-HOUR
PERIOD. THE SPATIAL COVERAGE OF THIS PRECIPITATION HAZARD IS CONSISTENT WITH
THE BACKGROUND EL NIñO. A SLIGHT RISK OF HIGH WINDS IS POSTED FOR THE EAST
COAST FOR WEEK-2 BASED ON A FAVORABLE SYNOPTIC PATTERN AND RECENT DETERMINISTIC
MODEL GUIDANCE.
A STRONG SURFACE LOW IS PREDICTED TO FORM OVER THE BERING SEA AT THE BEGINNING
OF THE PERIOD BRINGING ENHANCED SURFACE WINDS TO THE ALEUTIAN ISLANDS AND
COASTAL AREAS OF SOUTHWEST ALASKA. THEREFORE, A CORRESPONDING SLIGHT RISK OF
HIGH WINDS IS POSTED FOR JANUARY 6-10. ALTHOUGH ABOVE-NORMAL PRECIPITATION IS
FAVORED ACROSS MUCH OF THE SOUTHERN HALF OF ALASKA, PRECIPITATION AMOUNTS ARE
EXPECTED TO REMAIN BELOW HAZARDS THRESHOLDS.
FORECASTER: MELISSA OU
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