668
FXUS21 KWNC 081951
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 08 2024
SYNOPSIS: FOLLOWING A RESPITE FROM THE STORMINESS ADVERSELY AFFECTING THE
WESTERN CONTIGUOUS U.S. (CONUS) THIS WEEK, STRONG MID-LEVEL LOW PRESSURE IS
FORECAST TO RETURN, LEADING TO AN ELEVATED RISK OF HEAVY PRECIPITATION, HIGH
ELEVATION HEAVY SNOWFALL, AND HIGH WINDS ACROSS MANY PARTS OF WEST COAST AND
INTERIOR WEST DURING WEEK-2. SHORTWAVE ENERGY PREDICTED DOWNSTREAM FAVORS
INCREASED CHANCES FOR HEAVY PRECIPITATION ACROSS THE SOUTH-CENTRAL AND
SOUTHEASTERN CONUS, WITH THE POTENTIAL FOR ACCUMULATING HEAVY SNOW OVER THE
HIGHER ELEVATIONS OF THE APPALACHIANS LATER IN WEEK-2. AN EXPANDING AREA OF
MID-LEVEL HIGH PRESSURE OVER ALASKA IS EXPECTED TO LEAD TO UNSEASONABLE WARM
AND DRIER THAN NORMAL CONDITIONS THROUGHOUT MUCH OF THE STATE.
HAZARDS
HIGH RISK OF HEAVY PRECIPITATION FOR MUCH OF CALIFORNIA, SAT-MON, FEB 17-19.
MODERATE RISK OF HEAVY PRECIPITATION FOR CALIFORNIA, SOUTHERN NEVADA, AND PARTS
OF ARIZONA, FRI-WED, FEB 16-21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR CALIFORNIA, AND PARTS OF THE PACIFIC
NORTHWEST, NEVADA, AND THE DESERT SOUTHWEST, FRI-THU, FEB 16-22.
HIGH RISK OF HIGH ELEVATION HEAVY SNOW FOR THE SIERRA NEVADA RANGE OF
CALIFORNIA, SAT-MON, FEB 17-19.
MODERATE RISK OF HIGH ELEVATION HEAVY SNOW FOR THE SIERRA NEVADA RANGE OF
CALIFORNIA, FRI-WED, FEB 16-21.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF CALIFORNIA, AND PARTS OF
OREGON, FRI-THU, FEB 16-22.
MODERATE RISK OF HIGH ELEVATION HEAVY SNOW FOR THE MOGOLLON RIM OF THE DESERT
SOUTHWEST, SAT-TUE, FEB 17-20.
SLIGHT RISK OF HEAVY SNOW FOR PARTS OF THE HIGHER ELEVATIONS OF THE SOUTHERN
GREAT BASIN AND FOUR CORNERS, SAT-THU, FEB 17-22.
SLIGHT RISK OF HEAVY SNOW FOR PARTS OF THE NORTHERN ROCKIES AND NORTHERN HIGH
PLAINS, FRI-SUN, FEB, 16-18.
MODERATE RISK OF HIGH WINDS FOR CALIFORNIA AND PARTS OF NEVADA, FRI-WED, FEB
16-21.
SLIGHT RISK OF HIGH WINDS OVER MUCH OF THE WEST COAST THROUGH THE ROCKIES,
FRI-THU, FEB 16-22.
MODERATE RISK OF HEAVY PRECIPITATION OVER PARTS OF THE SOUTHERN PLAINS, AND
LOWER MISSISSIPPI VALLEY, FRI-SUN, FEB 16-18.
SLIGHT RISK OF HEAVY PRECIPITATION OVER THE SOUTHERN PLAINS, LOWER MISSISSIPPI
VALLEY, SOUTHEAST, AND LOWER MID-ATLANTIC, FRI-WED, FEB 16-21.
SLIGHT RISK OF HEAVY SNOW OVER THE SOUTHERN AND CENTRAL APPALACHIANS, SUN-WED,
FEB 18-21.
SLIGHT RISK OF HIGH WINDS OVER THE GREAT LAKES, OHIO VALLEY, APPALACHIANS,
MID-ATLANTIC, AND NORTHEAST, FRI-TUE, FEB 16-20.
FLOODING POSSIBLE OVER MUCH OF CALIFORNIA, FROM THE SIERRA FOOTHILLS TO THE
COAST.
FLOODING POSSIBLE OVER PARTS EASTERN TEXAS.
DETAILED SUMMARY
FOR SUNDAY FEBRUARY 11 - THURSDAY FEBRUARY 15:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY FEBRUARY 16 - THURSDAY FEBRUARY 22: BY LATE NEXT WEEK, DYNAMICAL
MODEL 500-HPA HEIGHT ANOMALY FORECASTS CONTINUE TO FEATURE LONG-WAVE TROUGHING
OVER THE EASTERN PACIFIC, WITH AMPLIFIED RIDGING CENTERED OVER NORTHWESTERN
CANADA AND ALASKA. THE ANOMALOUS MID-LEVEL TROUGHING OVER THE EASTERN PACIFIC
REMAINS FAVORED TO SHIFT EASTWARD AND RENEW THE RISK OF HAZARDOUS WEATHER
CONDITIONS OVER THE WESTERN CONUS HEADING INTO NEXT WEEKEND. HOWEVER, IT IS
WORTH NOTING THERE ARE SOME DIFFERENCES IN THE LATEST ENSEMBLE GUIDANCE WHICH
ADD TO SOME UNCERTAINTY IN REGARDS TO THE TIMING OF THE PRECIPITATION RELATED
HAZARDS DURING THE PERIOD. RELATIVE TO YESTERDAY, THE ECMWF FAVORS MORE
MID-LEVEL RIDGING TO PERSIST OVER THE NORTHWESTERN CONUS ON DAYS 8 AND 9 BEFORE
RETREATING POLEWARD, WHEREAS THE GEFS FAVORS A MORE EASTWARD SOLUTION OF THE
MEAN TROUGH AXIS LEADING TO MORE ENHANCED ONSHORE FLOW AND HIGHER PRECIPITATION
AMOUNTS OVER THE WEST COAST BY THE OUTSET OF WEEK-2. ANALYSIS OF THE CHANGES IN
RAW DAILY MEAN PRECIPITATION AMOUNTS BETWEEN THE GEFS AND ECMWF ALMOST APPEAR
OUT OF PHASE WITH EACH OTHER, AND THE LATEST INTEGRATED VAPOR TRANSPORT (IVT)
TOOLS DON'T OFFER MUCH CLARITY IN TERMS OF THE TIMING OF THE ENHANCED MOISTURE
SIGNALS, AND ALSO REMAIN FAIRLY WEAK IN TERMS OF ATMOSPHERIC RIVER POTENTIAL.
HOWEVER, DESPITE THESE DIFFERENCES IN THE EVOLUTION OF THE MID-LEVEL PATTERN
AND THE TIMING OF RAW PRECIPITATION AMOUNTS OVER THE WEST COAST, HIGHER SIGNALS
FOR HEAVY PRECIPITATION ARE DEPICTED IN THE RAW PRECIPITATION TOOLS, AS WELL AS
THE GEFS AND ECMWF PROBABILISTIC EXTREME TOOLS (PETS) RELATIVE TO YESTERDAY.
AND IN LIGHT OF THE ATMOSPHERIC RIVER ACTIVITY THAT HAS ADVERSELY IMPACTED MUCH
OF CALIFORNIA RECENTLY, A HIGH RISK OF HEAVY PRECIPITATION IS ISSUED FOR MUCH
OF THE STATE FOR FEB 17-19 WHERE THE 3-DAY AMOUNTS ARE HIGHEST AMONG THE
MULTI-MODEL GUIDANCE. WITHIN THE HIGHLIGHTED HIGH RISK AREA, THE ECMWF PET
SHOWS AT LEAST 50-60% CHANCES FOR 3-DAY AMOUNTS TO EXCEED THE 85TH PERCENTILE
AND 1 INCH, AND THE UNCALIBRATED ECMWF ALSO SHOWS 20-40% CHANCES FOR AMOUNTS TO
EXCEED 2 INCHES THROUGH THE MIDDLE OF WEEK-2. GIVEN THE POTENTIAL FOR HEAVY
PRECIPITATION FAVORED IN THE GEFS ON DAY 8 (FEB 16), A MODERATE RISK OF HEAVY
PRECIPITATION REMAINS ISSUED FOR CALIFORNIA AND INTO ARIZONA FOR FEB 16-21,
WHILE A BROADER SLIGHT RISK OF HEAVY PRECIPITATION IS ISSUED FOR FEB 16-22 DUE
TO THE PETS MAINTAINING INCREASED SIGNALS FOR AMOUNTS EXCEEDING THE 85TH
PERCENTILE, AND ENSEMBLES FAVORING THE PERSISTENT ANOMALOUS TROUGHING ALOFT.
THE PERSISTENCE OF ABOVE-NORMAL PRECIPITATION THROUGH WEEK-2 INDICATED IN THE
RAW AND CALIBRATED TOOLS SUPPORTS THE ADDITION OF A FLOODING POSSIBLE HAZARD
OVER CALIFORNIA FROM THE SIERRA FOOTHILLS TO THE COASTLINE. STREAMS AND RIVER
LEVELS ARE EXPECTED TO SUBSIDE SOMEWHAT DURING A DRY SPELL DURING WEEK-1,
HOWEVER THE HEAVY PRECIPITATION RISK MAY LEAD TO SHARP STREAM RESPONSES,
LOCALIZED FLOODING, AND MELTING SNOW FROM BUILD-UP IN THE LOWER ELEVATIONS IN
THE STATE.
BASED ON THESE WETTER TRENDS, INCREASED MOISTURE AVAILABILITY, AND SUPPORT FROM
THE SNOW WATER EQUIVALENT (SWE) PET, A CORRESPONDING HIGH, MODERATE, AND SLIGHT
RISK AREA FOR HEAVY SNOW IS POSTED OVER THE HIGHER ELEVATIONS OF CALIFORNIA FOR
FEB 17-19, FEB 16-21, AND FEB 16-22, RESPECTIVELY. FURTHER NORTH, SURFACE HIGH
PRESSURE DESCENDING FROM THE CANADIAN PRAIRIES IS EXPECTED TO BRING ANOMALOUSLY
COLDER TEMPERATURES INTO PARTS OF THE NORTHERN TIER. WHILE MINIMUM TEMPERATURES
AREN'T EXPECTED TO REACH HAZARD THRESHOLDS, THE RESULTANT UPSLOPE FLOW AND
INCREASED SIGNALS IN THE SWE PET SUPPORT A SLIGHT RISK OF HEAVY SNOW FOR FEB
16-18 OVER PARTS OF NORTHERN ROCKIES AND NORTHERN HIGH PLAINS. WITH AMPLIFIED
TROUGHING APPROACHING THE WEST COAST AND STRONGER PRESSURE GRADIENTS DEPICTED
IN MEAN SURFACE PRESSURE ANALYSES IN THE GEFS AND ECMWF, A MODERATE RISK OF
HIGH WINDS IS POSTED FOR FEB 16-21. THIS ADDITION IS ALSO SUPPORTED IN THE PET
GUIDANCE WHICH NOW SHOWS INCREASED CHANCES FOR WINDS EXCEEDING THE 85TH
PERCENTILE. A BROADER SLIGHT RISK AREA OF HIGH WINDS REMAINS POSTED AND COVERS
MUCH OF THE WESTERN CONUS FOR THE ENTIRETY OF WEEK-2 (FEB 16-22).
EARLY IN THE PERIOD, ENSEMBLES REMAIN CONSISTENT ON THE POTENTIAL FOR SHORTWAVE
ENERGY PROPAGATING EASTWARD OVER THE LOWER LATITUDES OVER NORTH AMERICA WITH
INCREASED PRECIPITATION AMOUNTS FAVORED OVER MEXICO AND THE GULF STATES. AT THE
SURFACE, A DEEPENING LOW PRESSURE AREA IS FAVORED OVER THE GULF OF MEXICO THAT
TRACKS EASTWARD INTO THE ATLANTIC, RESULTING IN AN INFLUX OF MOISTURE AND
INCREASED PRECIPITATION TOTALS ACROSS PARTS OF THE GULF STATES AND THE
SOUTHEAST THROUGH THE MIDDLE OF WEEK-2. THIS IS REFLECTED IN THE PETS, WHICH
CONTINUE TO SHOW INCREASED CHANCES FOR PRECIPITATION AMOUNTS EXCEEDING THE 85TH
PERCENTILE AND 1 INCH FROM SOUTHEASTERN TEXAS TO THE LOWER MISSISSIPPI EARLY IN
THE PERIOD, AND EXPANDING INTO THE SOUTHEAST AND LOWER MID-ATLANTIC DURING THE
MIDDLE OF THE PERIOD. BASED ON HIGHER CHANCES FOR PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE AND 1 INCH IN THE ECMWF PET OVER THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY, A MODERATE RISK OF HEAVY PRECIPITATION IS
ADDED TO THE OUTLOOK FOR FEB 16-18. TO CAPTURE THE EVOLUTION OF THE PREDICTED
SURFACE LOW, A BROAD SLIGHT RISK OF HEAVY PRECIPITATION IS ISSUED OVER MUCH OF
THE SOUTHEASTERN CONUS FOR FEB 16-21. PARTS OF EASTERN TEXAS HAVE REGISTERED
VERY LARGE PRECIPITATION SURPLUSES DURING THE PAST 30 DAYS WITH SEVERAL
LOCATIONS EXPERIENCING ELEVATED RIVER LEVELS. DUE TO INCREASED PRECIPITATION
FAVORED DURING THE NEXT TWO WEEKS, A FLOODING POSSIBLE SHAPE IS ALSO ADDED IN
THE REGION.
WHILE THERE IS GREATER UNCERTAINTY IN THE NORTHWARD EXTENT OF STORM TRACK AS IT
ENTERS THE ATLANTIC, THERE IS SUPPORT FOR ACCUMULATING AND POTENTIALLY HEAVY
SNOW ON THE BACKSIDE OF THE LOW. INCREASED SIGNALS ARE DEPICTED IN THE GEFS
BASED SWE TOOL OVER CENTRAL AND SOUTHERN APPALACHIANS AND A SLIGHT RISK OF
HEAVY SNOW IS ISSUED FOR FEB 18-21. THIS SNOW AREA MAY BE EXPANDED FURTHER
NORTHWARD AND ALSO INCLUDE LOWER ELEVATION AREAS OF THE EASTERN SEABOARD IN
UPCOMING OUTLOOKS ONCE ENSEMBLES GET A BETTER HANDLE ON THE EVENTUAL STORM
TRACK. OVER THE NORTHEASTERN CONUS, A SLIGHT RISK OF HIGH WINDS REMAINS ISSUED
FOR FEB 16-20 GIVEN PERSISTENT TROUGHING AND SURFACE LOW PRESSURE FORECAST OVER
THE CANADIAN MARITIMES WHICH MAY INDUCE STRENGTHENING PRESSURE GRADIENTS.
SIMILAR TO THE SNOW RISK FURTHER SOUTH, THIS WIND HAZARD IS SUBJECT TO CHANGE
IN UPCOMING OUTLOOKS BASED ON THE AFOREMENTIONED STORM TRACK OVER THE ATLANTIC
LATER IN THE PERIOD.
OVER ALASKA, MUCH OF THE ENHANCED ONSHORE FLOW OVER THE ALEUTIANS AND ALASKA
COAST LOOKS TO TIME OFF BY THE START OF WEEK-2 WITH MID-LEVEL ANOMALOUS RIDGING
FAVORED TO OVERSPREAD MUCH OF THE STATE. AS A RESULT, THE SLIGHT RISK OF HEAVY
PRECIPITATION IS DISCONTINUED FROM THE OUTLOOK. STRONG SURFACE HIGH PRESSURE
ESTABLISHED OVER THE YUKON TERRITORY MAY INDUCE GAP WINDS ACROSS THE SOUTHEAST
BUT THIS HAZARD POTENTIAL IS NOT SUPPORTED BY THE PETS.
FORECASTER: NICK NOVELLA
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