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FXUS21 KWNC 221940
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 22 2024
SYNOPSIS: EARLY IN THE PERIOD THERE IS GOOD AGREEMENT AMONG THE DYNAMICAL MODEL
TOOLS INDICATING ELEVATED POTENTIAL FOR HEAVY PRECIPITATION AND HIGH ELEVATION
SNOW IMPACTING PORTIONS OF THE WEST COAST. HOWEVER, THIS SIGNAL BECOMES MORE
DISORGANIZED BY THE MIDDLE OF THE PERIOD WITH SOME TOOLS PREDICTING A
CONTINUATION OF THE HEAVY PRECIPITATION AND OTHERS REDUCING THE RISK.
MEANWHILE, IN THE CENTRAL CONTIGUOUS UNITED STATES (CONUS) AN AREA OF
LOW-PRESSURE MAY DEVELOP AND BRING A PERIOD OF HEAVY PRECIPITATION, LOCALIZED
THUNDERSTORMS, AND HIGH WINDS TO PORTIONS OF THE MISSISSIPPI VALLEY, EASTERN
PLAINS, AND GREAT LAKES. IN ALASKA, ARCTIC HIGH PRESSURE OVER THE NORTHERN
PARTS OF THE STATE MAY HELP TO PROMOTE MUCH BELOW NORMAL TEMPERATURES AND GAP
WINDS ACROSS THE SOUTHERN MAINLAND.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR PERIODS OF HEAVY PRECIPITATION FOR THE
NORTHERN HALF OF CALIFORNIA, FRI, MAR 1.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FOR MUCH OF CALIFORNIA AND THE
PACIFIC NORTHWEST, FRI-TUE, MAR 1-MAR 5.
MODERATE RISK OF HEAVY SNOW FOR THE KLAMATH AND PORTIONS OF THE SIERRA NEVADA
MOUNTAINS, FRI-SAT, MAR 1-2.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR THE SIERRA NEVADA, KLAMATH, AND
CASCADE MOUNTAINS, FRI-TUE, MAR 1-MAR 5.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR MUCH OF THE WESTERN CONUS, FRI-TUE, MAR
1-MAR 5.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR PARTS OF THE NORTHERN ROCKIES,
FRI-TUE, MAR 1-MAR 5.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN
PLAINS AND LOWER-MISSISSIPPI VALLEY, SUN-TUE, MAR 3-5.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE MISSISSIPPI VALLEY, GREAT LAKES,
AND PLAINS, SUN-TUE, MAR 3-5.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF SOUTHWESTERN
ALASKA, FRI-SAT, MAR 1-2.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF SOUTHERN ALASKA,
FRI-MON, MAR 1-4.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR SOUTHERN COASTAL PORTIONS OF ALASKA
FROM NEAR YAKUTAT TO AROUND COLD BAY, FRI-TUE, MAR 1-5.
POSSIBLE FLOODING FOR PARTS OF THE NORTHERN HALF OF CALIFORNIA.
DETAILED SUMMARY
FOR SUNDAY FEBRUARY 25 - THURSDAY FEBRUARY 29:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY MARCH 01 - THURSDAY MARCH 07: MULTIPLE DYNAMICAL MODEL ENSEMBLE
MEANS SHOW AN AMPLIFIED MEAN WEEK-2 500-HPA HEIGHT PATTERN ACROSS MUCH OF THE
U.S. BUT CONTINUE TO BE IN FAIRLY LARGE DISAGREEMENT. THE ECENS INDICATES A
MORE AMPLIFIED MID-LEVEL TROUGH OVER THE NORTH PACIFIC COMPARED TO THE GEFS AT
THE BEGINNING OF THE PERIOD. BY THE MIDDLE OF THE PERIOD, THERE ARE INCREASING
DIFFERENCES AMONG THE MODELS REGARDING THE EVOLUTION OF THIS FEATURE. THE GEFS
MAINTAINS THIS FEATURE NEAR THE WEST COAST UNTIL THE END OF WEEK-2, WITH
MID-LEVEL SHORTWAVE TROUGHS MOVING ACROSS THE CENTRAL CONUS WHEREAS THE ECENS
INDICATES THE NORTH PACIFIC MID-LEVEL TROUGH SHIFTING EASTWARD TO THE CENTRAL
CONUS, WEAKENING THROUGHOUT WEEK-2. THESE MODEL DIFFERENCES TRANSLATE TO
DECREASING CONFIDENCE IN ASSOCIATED HAZARDS BY THE MIDDLE OF THE PERIOD.
THE INCREASED AMPLIFICATION OF THE MID-LEVEL TROUGH OVER THE NORTH PACIFIC
TRANSLATES TO INCREASED HEAVY PRECIPITATION SIGNALS FOR THE WEST COAST,
ESPECIALLY AT THE BEGINNING OF WEEK-2. A MODERATE RISK (AT LEAST A 40% CHANCE)
OF HEAVY PRECIPITATION IS POSTED ACROSS PARTS OF NORTHERN CALIFORNIA, MAR 1,
BASED ON ENHANCED INTEGRATED VAPOR TRANSPORT (IVT) SIGNALS IN THE GEFS, AND THE
ECENS (GEFS) PROBABILISTIC EXTREMES TOOL (PET) WHICH SHOW AT LEAST A 40% (30%)
CHANCE OF 3-DAY LIQUID EQUIVALENT TOTALS EXCEEDING THE 85TH PERCENTILE
CLIMATOLOGICALLY AND ONE INCH IN THIS AREA. AN ASSOCIATED MODERATE RISK OF HIGH
ELEVATION SNOW IS DESIGNATED FOR THE KLAMATH AND PORTIONS OF THE SIERRA NEVADA
MOUNTAINS, MAR 1-2, AN EXTRA DAY RELATIVE TO THE PRECIPITATION HAZARD DUE TO
HIGHER MOISTURE SIGNALS LINGERING IN HIGHER ELEVATIONS. A BROADER AREA OF
SLIGHT RISK (>20% CHANCE) IS CONTINUED FOR PERIODS OF HEAVY PRECIPITATION FOR
MUCH OF CALIFORNIA AND THE PACIFIC NORTHWEST WITH A SLIGHT RISK OF HEAVY SNOW
FOR THE HIGHER ELEVATIONS OF THE SIERRA NEVADA, KLAMATH AND CASCADE MOUNTAINS,
MAR 1-5. AN AREA OF POSSIBLE FLOODING IS ALSO POSTED FOR PORTIONS OF NORTHERN
CALIFORNIA WHERE A MODERATE RISK OF HEAVY PRECIPITATION IS FORECAST. HEAVY
RAINFALL FROM THE PAST SYSTEMS HAS LED TO SATURATED SOILS AND COULD ALLOW FOR A
QUICKER RISE IN STREAMS AND RIVERS. SIMILARLY, SHALLOW LANDSLIDES AND DEBRIS
FLOWS ARE ALWAYS POSSIBLE IN CALIFORNIA DURING PERIODS OF HEAVY RAINFALL IN
WINTER.
AS THIS MID-LEVEL TROUGH MOVES INLAND, RAW AND CALIBRATED GUIDANCE SUPPORTS A
SLIGHT RISK OF PERIODS OF HEAVY SNOW ACROSS THE HIGHER ELEVATIONS OF THE
NORTHERN ROCKIES SOUTH THROUGH THE NORTHERN WASATCH RANGE OF UTAH, MAR 1-5. A
SLIGHT CHANCE OF HIGH WINDS FOR MUCH OF THE WESTERN CONUS, MAR 1-5, INCLUDES
MUCH OF THE WESTERN CONUS DUE TO THE FAVORED DEEPENING OF THE MID-LEVEL TROUGH
IN THE NORTH PACIFIC.
THE DYNAMICAL MODELS, PARTICULARLY THE ECENS, IS PREDICTING AN AREA OF SURFACE
LOW PRESSURE TO DEVELOP IN THE LEE OF ROCKY MOUNTAINS IN RESPONSE TO THE
MID-LEVEL TROUGH MOVING INLAND. AHEAD OF THIS SYSTEM STRONG RETURN FLOW ALONG
THE GULF COAST MAY BRING WARM AND MOIST AIR INTO THE CENTRAL CONUS. IF THIS
SYSTEM DEVELOPS IT MAY BRING INCREASED CHANCES FOR HIGH WINDS AND HEAVY
PRECIPITATION TO PORTIONS OF THE SOUTHERN PLAINS AND LOWER-MISSISSIPPI VALLEY.
THE ECENS PET BRINGS >30% CHANCES FOR PRECIPITATION TO EXCEED THE 85TH
PERCENTILE FOR THE MIDDLE 3 DAYS OF THE PERIOD, FURTHER SUPPORTED BY RAW TOOLS
FOR THIS REGION. THE GEFS PET ALSO BRINGS A 20% CHANCE OF PRECIPITATION
EXCEEDING 1 INCH OF PRECIPITATION INTO THESE REGIONS. THEREFORE, A SLIGHT RISK
OF HEAVY PRECIPITATION IS HIGHLIGHTED FOR THE SOUTHERN PLAINS AND
LOWER-MISSISSIPPI VALLEY FOR MAR 3-5. FURTHER NORTH, THE HEAVY PRECIPITATION
THREAT IS LOWER BUT THERE REMAINS INCREASED POSSIBILITY OF HIGH WINDS ACROSS
MUCH OF THE MISSISSIPPI VALLEY AND GREAT LAKES. THEREFORE A BROADER SLIGHT RISK
OF HIGH WINDS IS POSTED FOR MAR 3-5 FOR MUCH OF THE CENTRAL CONUS.
IN ALASKA, AN AREA OF ARCTIC HIGH PRESSURE IS FORECAST ACROSS THE NORTHERN
PARTS OF THE STATE AND THE YUKON, WITH SURFACE LOW-PRESSURE OVER THE GULF OF
ALASKA. THIS PATTERN FAVORS INCREASED CHANCES OF GAP WINDS OVER PARTS OF THE
SOUTHERN ALASKA COASTLINE FROM COLD BAY TO YAKUTAT THROUGH THE MIDDLE OF THE
WEEK-2 PERIOD. THUS, A SLIGHT RISK OF HIGH WINDS IS MAINTAINED FOR MAR 1-5
ACROSS THE AREA. THE PETS CONTINUE TO SHOW ENHANCED PROBABILITIES FOR MUCH
BELOW NORMAL TEMPERATURES RELATIVE TO PREVIOUS GUIDANCE, AND INDICATE AT LEAST
A 40% CHANCE OF MINIMUM TEMPERATURES FALLING TO THE LOWEST 5TH PERCENTILE
CLIMATOLOGICALLY ACROSS THE SOUTHWESTERN MAINLAND AND ALASKA PENINSULA ON DAYS
8 AND 9 (MAR 1-2). A MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES IS
DESIGNATED FOR PARTS OF SOUTHWESTERN ALASKA SOUTHWEST OF A LINE FROM PRINCE
WILLIAM SOUND TO NEAR ANCHORAGE, MAR 1-2. A BROADER AREA OF SLIGHT RISK IS
HIGHLIGHTED ACROSS SOUTHERN ALASKA, MAR 1-4. HIGH WINDS ACROSS THE SOUTHERN
COAST OF ALASKA COULD CONTRIBUTE TO ANOMALOUSLY LOW WIND CHILL VALUES.
FORECASTER: RYAN BOLT
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