593
FXUS21 KWNC 182020
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 18 2024
SYNOPSIS: MOIST AIR OFF THE GULF OF MEXICO IS FORECAST TO INTERACT WITH A STORM
SYSTEM OVER THE GREAT PLAINS BEGINNING MID-LATE IN WEEK-1 THAT COULD SUPPORT
LINGERING HEAVY PRECIPITATION INTO EARLY WEEK-2 FOR PORTIONS OF THE LOWER
MISSISSIPPI AND TENNESSEE VALLEYS, SOUTHERN APPALACHIANS, AND SOUTHEAST U.S.
STORMY PACIFIC ONSHORE FLOW IS FORECAST TO CONTINUE FOR NORTHERN PORTIONS OF
THE WEST COAST EARLY IN THE FORECAST PERIOD, SUPPORTING THE INCREASED POTENTIAL
FOR HEAVY PRECIPITATION AND HEAVY SNOW FOR THE HIGHER ELEVATIONS ACROSS THE
PACIFIC NORTHWEST. MUCH BELOW NORMAL TEMPERATURES ARE POSSIBLE ACROSS CENTRAL
AND SOUTHWESTERN MAINLAND OF ALASKA AT THE BEGINNING OF WEEK-2 ASSOCIATED WITH
STRONG SURFACE HIGH PRESSURE EXTENDING FROM THE YUKON TO THESE REGIONS.
HAZARDS
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE LOWER MISSISSIPPI AND
TENNESSEE VALLEYS, SOUTHERN APPALACHIANS, AND SOUTHEAST U.S., FRI-SAT, JAN
26-27.
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PARTS OF THE PACIFIC NORTHWEST,
FRI-SAT, JAN 26-27.
SLIGHT RISK FOR HEAVY SNOW FOR PORTIONS OF THE CASCADE MOUNTAINS, FRI-SAT, JAN
26-27.
FLOODING POSSIBLE FOR THE WESTERN FOOTHILLS OF THE CASCADE MOUNTAINS.
SLIGHT RISK FOR HEAVY SNOW FOR THE NORTHERN ROCKIES, FRI-SAT, JAN 26-27.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL AND
SOUTHWESTERN ALASKA MAINLAND, FRI-SUN, JAN 26-28.
DETAILED SUMMARY
FOR SUNDAY JANUARY 21 - THURSDAY JANUARY 25:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JANUARY 26 - THURSDAY FEBRUARY 01: AS SURFACE HIGH PRESSURE
ASSOCIATED WITH THE ONGOING COLD SNAP OVER THE CONTIGUOUS U.S. (CONUS) SHIFTS
EASTWARD, MOIST RETURN FLOW IS FAVORED TO DEVELOP OVER THE GREAT PLAINS. MODELS
DEPICT A SHORTWAVE TROUGH MOVING OFF THE ROCKIES DURING WEEK-1 AND DEVELOPING
HEAVY PRECIPITATION AS IT MOVES EASTWARD. WHILE THE EFFECTS OF THIS SYSTEM ARE
NOW MOSTLY WITHIN THE WEEK-1 PERIOD, THE POTENTIAL FOR HEAVY PRECIPITATION MAY
LINGER INTO WEEK-2. THE ECMWF AND GEFS PROBABILISTIC EXTREMES TOOLS (PETS) BOTH
INDICATE AT LEAST A 20% PROBABILITY OF 3-DAY PRECIPITATION EXCEEDING THE 85TH
PERCENTILE AND AT LEAST 1 INCH FOR MUCH OF THE SOUTHEASTERN CONUS. THE ECMWF
PET CONTINUES TO SHOW HIGHER PROBABILITIES THAN THE GEFS, INDICATING AT LEAST A
40% OF 3-DAY PRECIPITATION (JAN 26-28) EXCEEDING THESE THRESHOLDS WHILE THE
GEFS REMAINS AT 20%. DUE TO DECREASING SIGNALS FOR HEAVY PRECIPITATION A
MODERATE RISK OF HEAVY PRECIPITATION IS NOT DESIGNATED IN TODAY'S OUTLOOK AND A
SLIGHT RISK IS MAINTAINED FOR JAN 26-27. ANTECEDENT HEAVY RAINFALL DURING
WEEK-1 COMBINED WITH EXPECTED HEAVY RAIN MAY LEAD TO LOCALIZED FLASH FLOODING.
THERE CONTINUES TO BE GOOD AGREEMENT ACROSS MULTIPLE MODELS SHOWING A MID-LEVEL
TROUGH OVER THE NORTHEAST PACIFIC APPROACHING THE WEST COAST EARLY IN WEEK-2.
THIS PATTERN SUPPORTS ENHANCED CHANCES FOR PERIODS OF HEAVY PRECIPITATION FOR
THE PACIFIC NORTHWEST. THE GEFS AND ECMWF INTEGRATED VAPOR TRANSPORT (IVT) TOOL
SHOWS INCREASED CHANCES FOR ENHANCED VALUES (>250 KG/M/S) FOR THIS REGION FOR
THE 8 TO 10 DAY PERIOD (JAN 26-28). THE SOUTHWARD EXTENT OF THE SLIGHT RISK OF
HEAVY PRECIPITATION ACROSS THE PACIFIC NORTHWEST IS SLIGHTLY TRIMMED BACK DUE
TO DECREASING WET SIGNALS ACROSS THE REGION AS THE EVENT TIMES OUT. THE PETS
SHOW AT LEAST A 20% CHANCE OF 3-DAY LIQUID EQUIVALENT EXCEEDING THE 85TH
PERCENTILE AND 2 INCHES AT THE BEGINNING OF THE PERIOD IN THE HIGHLIGHTED AREA.
JANUARY 26TH AND 27TH IS INCLUDED IN THE RISK PERIOD WHERE ENSEMBLE MEANS SHOW
THE GREATEST LIKELIHOOD OF HEAVY DAILY PRECIPITATION TOTALS. THE CASCADE
MOUNTAINS HAVE A SLIGHT RISK OF HEAVY SNOW POSTED FOR THE SAME PERIOD. FLOODING
IS POSSIBLE FOR THE WESTERN FOOTHILLS OF THE CASCADES AS HEAVY PRECIPITATION
AND SNOW CONTINUE TO AFFECT THE REGION AND TEMPERATURES EXPECTED TO RISE
QUICKLY DURING THE FORECAST PERIOD. THE ORIENTATION OF THE SURFACE LOW
ASSOCIATED WITH THIS TROUGH IS LESS CONDUCIVE TO HIGH WINDS COMPARED TO
YESTERDAY, THUS NO ASSOCIATED WIND HAZARDS ARE POSTED TODAY ALTHOUGH THERE
COULD BE LOCALIZED HIGH WINDS MOST LIKELY FOR NORTHWESTERN COASTAL WASHINGTON.
MOISTURE FROM THE AFOREMENTIONED SHORTWAVE MAY EXTEND INLAND, SUPPORTING
CONTINUED SLIGHT RISK OF HEAVY SNOW FOR THE NORTHERN ROCKIES JAN 26 TO 27.
SURFACE HIGH PRESSURE CENTERED OVER THE FOUR CORNERS AND NORTHERN PLAINS MAY
LIMIT THE POTENTIAL FOR ENHANCED SNOW FURTHER SOUTH, THUS THE SLIGHT RISK FOR
HEAVY SNOW OVER THE FOUR CORNERS IN YESTERDAY'S OUTLOOK IS REMOVED TODAY.
ENSEMBLE SOLUTIONS FROM THE GEFS, ECMWF, AND CMCE ALL INDICATE SURFACE LOW
PRESSURE SYSTEMS IN THE GULF OF ALASKA THROUGHOUT THE WEEK-2 PERIOD, RESULTING
IN ELEVATED CHANCES FOR HIGH WIND AND HEAVY PRECIPITATION FOR THE SOUTHERN AND
SOUTHEASTERN COASTS OF ALASKA, INCLUDING THE POTENTIAL FOR GAP WINDS. A STRONG
YUKON SURFACE HIGH IS FAVORED IN MULTIPLE MODEL SOLUTIONS THAT SUPPORTS COLD
NORTHERLY OUTFLOW AND POTENTIALLY STRONG GAP WINDS EXTENDING FROM THE ALASKA
PENINSULA TO THE SOUTHEAST MAINLAND AT THE BEGINNING OF WEEK-2. DUE TO HIGH
UNCERTAINTY REGARDING THE PRECISE LOCATION OF WHERE GAP WINDS WOULD BE LOCATED,
AN ASSOCIATED HIGH WIND HAZARD IS NOT SPECIFIED AT THIS TIME. STRONG SURFACE
HIGH PRESSURE EXTENDING FROM THE YUKON TO OVER THE MAINLAND EXCLUDING
SOUTHEASTERN ALASKA MAY BRING COLD ARCTIC AIR FROM THE NORTH. A SLIGHT RISK OF
MUCH BELOW NORMAL TEMPERATURES IS HIGHLIGHTED ACROSS PORTIONS OF CENTRAL AND
SOUTHWESTERN ALASKA MAINLAND, JAN 26-28, WHERE PETS ARE IN GOOD AGREEMENT
INDICATING MINIMUM TEMPERATURES FALLING IN THE LOWEST 10TH PERCENTILE
CLIMATOLOGICALLY. SUB ZERO TEMPERATURES ARE POSSIBLE ACROSS THE SOUTHWESTERN
MAINLAND WHILE CENTRAL PORTIONS MAY FALL BELOW -40 DEG F.
FORECASTER: MELISSA OU
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