487
FXUS21 KWNC 081949
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 08 2023
SYNOPSIS: STRONG MID-LEVEL LOW PRESSURE IS FORECAST TO SHIFT INLAND TO THE WEST
NEXT WEEK WITH AN INCREASED RISK OF HEAVY PRECIPITATION ACROSS CALIFORNIA AND
HEAVY SNOW FOR THE SIERRA NEVADA MOUNTAINS. ACCUMULATING SNOW MAY OVERSPREAD
THE HIGHER ELEVATIONS OF THE GREAT BASIN AND CENTRAL ROCKIES FROM NOVEMBER 16
TO 18. SURFACE LOW PRESSURE DEVELOPMENT IS POSSIBLE OVER THE CENTRAL GREAT
PLAINS BY NOV 18, BUT HEAVY PRECIPITATION IS BECOMING LESS LIKELY ACROSS THE
CENTRAL U.S. DURING WEEK-2. MID-LEVEL LOW PRESSURE IS FORECAST OVER THE BERING
SEA EARLY IN WEEK-2 WITH A SURFACE LOW PRESSURE SYSTEM TRACKING FROM THE BERING
STRAIT TO NORTHWESTERN ALASKA ON NOVEMBER 16.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR THE COASTAL RANGES OF CALIFORNIA AND
SIERRA NEVADA MOUNTAINS, THU, NOV 16.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF CALIFORNIA, THU-FRI, NOV 16-17.
MODERATE RISK OF HEAVY SNOW FOR THE SIERRA NEVADA MOUNTAINS, THU, NOV 16.
SLIGHT RISK OF HEAVY SNOW FOR THE SIERRA NEVADA MOUNTAINS, THU-FRI, NOV 16-17.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF UTAH AND COLORADO,
THU-SAT, NOV 16-18.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE WEST, THU-SAT, NOV 16-18.
SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA, KODIAK ISLAND,
AND COASTAL SOUTHWESTERN ALASKA, THU, NOV 16.
SLIGHT RISK OF HEAVY PRECIPITATION FOR EASTERN OKLAHOMA, EASTERN TEXAS, MIDDLE
TO LOWER MISSISSIPPI VALLEY, AND OHIO VALLEY, FRI-SUN, NOV 17-19.
DETAILED SUMMARY
FOR SATURDAY NOVEMBER 11 - WEDNESDAY NOVEMBER 15:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY NOVEMBER 16 - WEDNESDAY NOVEMBER 22: THE 0Z GEFS, ECMWF, AND
CANADIAN ENSEMBLE MEANS REMAIN CONSISTENT AND IN GOOD AGREEMENT THAT A HIGHLY
AMPLIFIED 500-HPA TROUGH PROGRESSES EAST FROM THE NORTHEASTERN PACIFIC TO THE
WESTERN CONTIGUOUS U.S. (CONUS) BY THE BEGINNING OF WEEK-2. BASED ON GOOD MODEL
CONSISTENCY AND 24-HOUR PRECIPITATION AMOUNTS FROM THE GEFS AND ECMWF ENSEMBLE
MEANS, A MODERATE RISK OF HEAVY PRECIPITATION IS POSTED FOR THE COASTAL RANGES
OF CALIFORNIA AND THE SIERRA NEVADA MOUNTAINS ON NOV 16. A WETTER MODEL TREND
PROMPTED INCLUDING SOUTHERN CALIFORNIA IN THIS MODERATE RISK. IT SHOULD BE
NOTED THAT THE HEAVIEST PRECIPITATION THROUGHOUT CALIFORNIA MAY OCCUR AS EARLY
AS NOV 15. ALTHOUGH THE HEAVIEST PRECIPITATION MAY TRIGGER LOCALIZED FLOODING,
THE PREDICTED SHORT DURATION OF THIS HEAVY PRECIPITATION AND 28-DAY AVERAGE
STREAMFLOWS GENERALLY CLOSE TO AVERAGE ARE EXPECTED TO LIMIT THE RISK OF MAJOR
FLOODING.
MODEL GUIDANCE REMAINS CONSISTENT THAT HEAVY SNOW AFFECTS THE SIERRA NEVADA
MOUNTAINS AS THE ANOMALOUS TROUGH SHIFTS INLAND AND SNOW LEVELS LOWER.
THEREFORE, A MODERATE RISK OF HEAVY SNOW CONTINUES FOR THE SIERRA NEVADA
MOUNTAINS ON NOV 16. ACCUMULATING SNOWFALL, ALBEIT WITH LOWER AMOUNTS, SUPPORTS
A SLIGHT RISK OF HEAVY SNOW ACROSS THE HIGHER ELEVATIONS OF UTAH AND COLORADO
FROM NOV 16 TO 18. ALSO, DURING THIS TIME PERIOD, A SLIGHT RISK OF HIGH WINDS
(NOV 16-18) COVERS CALIFORNIA, THE GREAT BASIN, SOUTHWEST, CENTRAL TO SOUTHERN
ROCKIES, AND ADJACENT AREAS OF THE HIGH PLAINS BASED ON THE EVOLVING 500-HPA
PATTERN.
THE GEFS AND ECMWF ENSEMBLE MEANS ARE IN BETTER AGREEMENT TODAY WITH SURFACE
LOW PRESSURE DEVELOPMENT ACROSS THE CENTRAL GREAT PLAINS BY NOV 18 WITH A
SUBSEQUENT TRACK TO THE MIDWEST. THE ECMWF MODEL HAS SLIGHTLY BACKED OFF ON ITS
SIGNAL FOR HEAVY PRECIPITATION AND THERE IS LITTLE TO NO SUPPORT FROM THE
GFS-BASED TOOLS. HOWEVER, THE UNCALIBRATED ECMWF CONTINUES TO SUPPORT A SLIGHT
RISK FOR HEAVY PRECIPITATION FOR MUCH OF THE CENTRAL U.S. FROM NOV 17 TO 19.
PRIOR TO WEEK-2, AN AMPLIFIED TROUGH IS LIKELY TO LEAD TO SURFACE LOW PRESSURE
DEVELOPMENT OVER THE BERING SEA. BY NOV 16TH, THE 0Z GEFS AND ECMWF ENSEMBLE
MEANS DEPICT THIS LOW PRESSURE SYSTEM TRACKING FROM NEAR THE BERING STRAIT TO
NORTHWESTERN MAINLAND ALASKA. A STRONG PRESSURE GRADIENT SUPPORTS A SLIGHT RISK
OF HIGH WINDS FOR COASTAL SOUTHWESTERN ALASKA, THE ALEUTIANS, AND ALASKA
PENINSULA ON NOV 16. WITH THE PARENT LOW PRESSURE SYSTEM TRACKING WELL TO THE
NORTH AND DIMINISHING SUPPORT FROM THE PRECIPITATION TOOLS, THE HEAVY
PRECIPITATION HAZARD FOR SOUTHEASTERN ALASKA IN PREVIOUS OUTLOOKS IS
DISCONTINUED. THE AMPLIFIED 500-HPA TROUGH OVER THE BERING SEA AND ENHANCED
ONSHORE FLOW COULD BRING HEAVY SNOW TO INTERIOR CENTRAL TO SOUTHWESTERN ALASKA,
ESPECIALLY EARLY IN WEEK-2.
THE GFS MODEL CONTINUES TO BE THE MOST BULLISH ON TROPICAL CYCLONE (TC)
DEVELOPMENT ACROSS THE CARIBBEAN SEA BY WEEK-2 WITH MANY OF ITS ENSEMBLE
MEMBERS DEPICTING A NORTHEASTWARD TRACK ACROSS JAMAICA, CUBA, AND THE BAHAMAS.
HOWEVER, THE ECMWF ENSEMBLE MEMBERS FAVOR SLOWER TC DEVELOPMENT OVER THE
SOUTHWESTERN CARIBBEAN SEA. FUTURE MODEL RUNS WILL BE CLOSELY MONITORED TO SEE
IF ANY HAZARDS ARE WARRANTED FOR SOUTH FLORIDA OR THE FLORIDA KEYS.
FORECASTER: BRAD PUGH
CLICK HERE TO GO TO PREVIOUS BULLETINS.
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