054
FXUS21 KWNC 281939
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 28 2023
SYNOPSIS: MID-LEVEL LOW PRESSURE IS EXPECTED TO TRACK ACROSS THE SOUTHERN TIER
OF THE CONTIGUOUS U.S. (CONUS) ON JANUARY 5 AND 6. AS THIS MID-LEVEL LOW
PRESSURE PROGRESSES EASTWARD, A SURFACE LOW PRESSURE SYSTEM IS LIKELY TO
DEVELOP ALONG THE GULF COAST WITH A SUBSEQUENT TRACK NORTHEASTWARD NEAR THE
EAST COAST. FROM JANUARY 6 TO 8, MID-LEVEL LOW PRESSURE IS EXPECTED TO SHIFT
EAST FROM THE WEST COAST TO THE ROCKIES AND GREAT PLAINS. 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 HEAVY PRECIPITATION FOR PARTS OF THE SOUTHEAST, FRI-SAT, JAN
5-6.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE GULF COAST, SOUTHEAST, AND
EAST COAST, FRI-THU, JAN 5-11.
SLIGHT RISK OF HEAVY SNOW FOR THE SOUTHERN TO CENTRAL APPALACHIANS AND PARTS OF
THE NORTHEAST, SAT-SUN, JAN 6-7.
MODERATE RISK OF HEAVY SNOW FOR THE KLAMATH AND SIERRA NEVADA MOUNTAINS,
SAT-SUN, JAN 6-7.
SLIGHT RISK OF HEAVY SNOW FOR THE KLAMATH AND SIERRA NEVADA MOUNTAINS, SAT-SUN,
JAN 6-7.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF THE INTERIOR WEST,
SAT-MON, JAN 6-8.
SLIGHT RISK OF HEAVY PRECIPITATION FOR NORTHERN CALIFORNIA AND THE PACIFIC
NORTHWEST, SAT-SUN, JAN 6-7.
SLIGHT RISK OF HIGH WINDS FOR THE WEST AND HIGH PLAINS, SAT-TUE, JAN 6-9.
SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA, AND COASTAL
SOUTHWESTERN ALASKA, FRI-THU, JAN 5-11.
DETAILED SUMMARY
FOR SUNDAY DECEMBER 31 - THURSDAY JANUARY 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JANUARY 05 - THURSDAY JANUARY 11: THE 0Z GEFS, ECMWF, AND CANADIAN
ENSEMBLE MEANS DEPICT A 500-HPA SHORTWAVE TROUGH EJECTING FROM THE SOUTHWEST
LATER NEXT WEEK AND RESULTING IN SURFACE LOW DEVELOPMENT ACROSS THE LOWER
MISSISSIPPI VALLEY OR SOUTHEAST BY JANUARY 6. THIS EVOLVING PATTERN ALONG WITH
24-HOUR FORECAST AMOUNTS FROM THE ENSEMBLE MEANS SUPPORT A MODERATE RISK OF
HEAVY PRECIPITATION FOR PARTS OF THE LOWER MISSISSIPPI VALLEY, GULF COAST AND
SOUTHEAST ON JANUARY 5 AND 6. SINCE MANY GEFS AND ECMWF ENSEMBLE MEMBERS HAVE A
STRENGTHENING LOW PRESSURE SYSTEM TRACKING NORTHWARD NEAR THE EAST COAST, A
SLIGHT RISK OF HEAVY SNOW (JANUARY 6 AND 7) IS POSTED FOR THE SOUTHERN TO
CENTRAL APPALACHIANS AND PARTS OF THE NORTHEAST. PRECIPITATION TYPE IS MORE
UNCERTAIN ACROSS THE LOWER ELEVATIONS OF THE MID-ATLANTIC. A SECOND LOW
PRESSURE SYSTEM IS EXPECTED TO AFFECT THE GULF COAST AND EAST BY THE END OF
WEEK-2 AS AN AMPLIFIED TROUGH APPROACHES FROM THE WESTERN AND CENTRAL CONUS.
THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOLS (PETS) SUPPORT A BROAD SLIGHT
RISK FOR HEAVY PRECIPITATION AND IT IS VALID THROUGH THE ENTIRETY OF WEEK-2.
THE SPATIAL COVERAGE OF THIS PRECIPITATION HAZARD IS CONSISTENT WITH THE
BACKGROUND EL NIñO.
MODEL GUIDANCE CONTINUES TO SHOW A FULL-LATITUDE TROUGH PROGRESSING EAST FROM
THE WEST COAST TO THE ROCKIES AND GREAT PLAINS FROM JANUARY 6 TO 8. BASED ON
GOOD MODEL AGREEMENT AND CONTINUITY, THE AMPLITUDE OF THE 500-HPA TROUGH,
24-HOUR PRECIPITATION AMOUNTS FROM MULTI-MODEL ENSEMBLE MEANS, AND THE GEFS
PET, A MODERATE RISK OF HEAVY SNOW IS POSTED FOR THE KLAMATH AND SIERRA NEVADA
MOUNTAINS ON JANUARY 6 AND 7. THE EASTWARD PROGRESSION OF THE AMPLIFIED TROUGH
ALONG WITH THE GEFS PET SUPPORT A SLIGHT RISK OF HEAVY SNOW FOR MANY OF THE
HIGH-ELEVATION AREAS OF THE WEST ALONG WITH A BROAD SLIGHT RISK OF HIGH WINDS
THROUGHOUT THE WEST AND MUCH OF THE HIGH PLAINS. THE SNOW HAZARD FOR THE
CASCADES AND SIERRA NEVADA MOUNTAINS TIMES OFF AFTER JANUARY 7 AFTER THE
LONGWAVE TROUGH AXIS SHIFTS WELL INLAND. THE SNOW HAZARD FOR THE INTERIOR WEST
AND WIND HAZARD CONTINUE THROUGH JANUARY 8 AND 9, RESPECTIVELY.
AS THE AMPLIFIED TROUGH SHIFTS EAST TO THE ROCKIES, THERE IS AN INCREASED
CHANCE OF SURFACE LOW DEVELOPMENT ACROSS THE GREAT PLAINS LATER IN WEEK-2. A
SNOW HAZARD MAY BE NEEDED FOR PARTS OF THE GREAT PLAINS AND MIDWEST IN
SUBSEQUENT OUTLOOKS.
A PAIR OF LOW PRESSURE SYSTEMS ARE EXPECTED TO DEVELOP OVER THE BERING SEA
PRIOR TO WEEK-2 AND THEN ALSO DURING THIS OUTLOOK PERIOD. THESE LOW PRESSURE
SYSTEMS ARE FORECAST TO BRING 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 5-11. ALTHOUGH ABOVE-NORMAL PRECIPITATION
IS FAVORED ACROSS MUCH OF ALASKA, PRECIPITATION AMOUNTS ARE EXPECTED TO REMAIN
BELOW HAZARDS THRESHOLDS.
FORECASTER: BRAD PUGH
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