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FXUS21 KWNC 011819
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT NOVEMBER 01 2023
SYNOPSIS: TODAY’S DYNAMICAL MODELS DEPICT A MORE PROGRESSIVE FLOW PATTERN
ACROSS THE EASTERN CONTIGUOUS U.S. (CONUS) DURING WEEK-2 COMPARED TO YESTERDAY
LEADING TO MORE UNCERTAINTY IN THE HAZARDS OUTLOOK. SURFACE LOW PRESSURE IS
FORECAST TO MOVE ACROSS THE MIDWEST AND NORTHEAST LATE IN WEEK-1, WITH THE
POSSIBILITY OF ANOTHER WAVE OF LOW PRESSURE PASSING THROUGH THE EAST EARLY IN
WEEK-2, ALTHOUGH MODELS DIFFER IN THE TRACK AND THE AMOUNT OF MOISTURE.
MID-LEVEL LOW PRESSURE OVER THE NORTHEASTERN PACIFIC AND RESULTANT ENHANCED
ONSHORE FLOW MAY BRING HEAVY PRECIPITATION AND EPISODES OF HIGH WINDS TO THE
PACIFIC NORTHWEST AND NORTHERN CALIFORNIA. STRENGTHENING PRESSURE GRADIENTS
ASSOCIATED WITH SURFACE HIGH PRESSURE OVER THE GREAT BASIN MAY LEAD TO EPISODES
OF SANTA ANA WINDS OVER SOUTHERN CALIFORNIA EARLY IN THE PERIOD.
HAZARDS
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHEAST,
THU-SUN, NOV 9-12.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND PARTS OF
NORTHERN CALIFORNIA, THU-MON, NOV 9-13.
SLIGHT RISK OF HIGH WINDS OVER COASTAL PARTS OF THE PACIFIC NORTHWEST AND
NORTHERN CALIFORNIA, THU-MON, NOV 9-13.
SLIGHT RISK OF HIGH WINDS OVER PARTS OF THE NORTHEAST, THU, NOV 9.
SLIGHT RISK OF HIGH WINDS OVER PARTS OF SOUTHERN CALIFORNIA, THU-FRI, NOV 9-10.
DETAILED SUMMARY
FOR SATURDAY NOVEMBER 04 - WEDNESDAY NOVEMBER 08:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY NOVEMBER 09 - WEDNESDAY NOVEMBER 15: SURFACE LOW PRESSURE IS
FORECAST TO TRACK ACROSS THE MIDWEST AND NORTHEAST LATE IN WEEK-1 AND MOVE INTO
EASTERN CANADA BY THE OUTSET OF WEEK-2. IN THE WAKE OF THIS SYSTEM, A TIGHT
PRESSURE GRADIENT IS FORECAST ACROSS PORTIONS OF THE NORTHEAST AND NEW ENGLAND
SUPPORTING A SLIGHT RISK FOR HIGH WINDS REMAINING IN PLACE ON DAY-8 (11/9).
FOLLOWING THE DEPARTURE OF THIS STORM SYSTEM, THERE IS MORE UNCERTAINTY IN THE
FORECAST COMPARED TO YESTERDAY.
BOTH THE 0Z GEFS AND ECMWF ENSEMBLES DEPICT SHORTWAVE TROUGHING MOVING THROUGH
THE EAST EARLY IN WEEK-2 AND POTENTIALLY ANOTHER WAVE OF SURFACE LOW PRESSURE
DEVELOPING ACROSS THE EASTERN CONUS. SEVERAL 0Z GEFS ENSEMBLE MEMBERS ALSO SHOW
SOME INTERACTION WITH A TROPICAL SYSTEM FORECAST TO DEVELOP ACROSS THE
CARIBBEAN WITH MOISTURE POTENTIALLY BEING PULLED NORTHWARD, ENHANCING
PRECIPITATION CHANCES ACROSS THE EASTERN SEABOARD. ALTHOUGH THE ECMWF
PROBABILISTIC EXTREMES TOOL (PET) DEPICTS AT LEAST A 20 PERCENT CHANCE OF 3-DAY
PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH
EXTENDING FROM THE LOWER MISSISSIPPI VALLEY TO THE MID-ATLANTIC AND COASTAL
NORTHEAST EARLY IN WEEK-2, THERE IS LITTLE SIGNAL IN THE GEFS PET. GIVEN THE
DIFFERENCES IN MODEL SOLUTIONS, NO RELATED PRECIPITATION HAZARD IS POSTED.
ADDITIONALLY, THERE IS LESS SUPPORT SYNOPTICALLY FOR LAKE EFFECT SNOW GIVEN THE
MORE PROGRESSIVE PATTERN, THUS THE SLIGHT RISK FOR HEAVY SNOW IS DISCONTINUED.
WHILE THE DETERMINISTIC 6Z AND 12Z GFS RUNS DEPICT TEMPERATURES COLD ENOUGH TO
SUPPORT SNOW ACROSS PARTS OF THE INTERIOR NORTHEAST ASSOCIATED WITH THE
AFOREMENTIONED SURFACE LOW PRESSURE SYSTEM, THE DETERMINISTIC 0Z ECMWF
INDICATES STRONGER SOUTHERLY FLOW AND WARMER SURFACE TEMPERATURES REDUCING THE
CHANCES FOR ACCUMULATING SNOW.
THERE HAS ALSO BEEN A NOTICEABLE WARMING TREND IN TEMPERATURES ACROSS THE
SOUTHEASTERN CONUS COMPARED TO YESTERDAY DUE TO INCREASING SOUTHERLY FLOW AHEAD
OF THE INCOMING SHORTWAVE TROUGH EARLY IN THE PERIOD. THE NORTHERN EXTENT OF
THE WARMING IS UNCERTAIN, WITH THE 0Z ECMWF ENSEMBLE EXTENDING ANOMALOUSLY WARM
TEMPERATURES UP THROUGH PARTS OF THE MID-ATLANTIC, WHILE THE 0Z AND 6Z GEFS
SOLUTIONS MAINTAIN A RELATIVELY COLDER PATTERN. BOTH THE ECMWF AND GEFS PETS
AGREE ON THE STRONGEST COLD SIGNAL REMAINING OVER PARTS OF THE INTERIOR
NORTHEAST AND NEW ENGLAND, WITH BOTH TOOLS DEPICTING AT LEAST A 20 PERCENT
CHANCE MINIMUM TEMPERATURES FALL BELOW THE 15TH CLIMATOLOGICAL PERCENTILE AND
20 DEG F, SUPPORTING THE SLIGHT RISK FOR MUCH BELOW NORMAL TEMPERATURES TO
REMAIN IN PLACE OVER THESE AREAS FOR NOV 9-12. WHILE SUBFREEZING OVERNIGHT
TEMPERATURES MAY EXTEND TO AREAS FARTHER SOUTH, IMPACTS TO VEGETATION ARE
EXPECTED TO BE MINIMAL DUE TO THE END OF THE GROWING SEASON ACROSS MANY AREAS,
WITH THE HAZARD SCOPED TO WHERE THE STRONGEST SIGNALS FOR BELOW NORMAL
TEMPERATURES ARE IN THE TOOLS. LATER IN WEEK-2, BOTH THE 0Z GEFS AND ECMWF
ENSEMBLES DEPICT POSITIVE MID-LEVEL HEIGHT ANOMALIES BUILDING ACROSS MOST OF
THE CONUS, WHICH FAVOR A TREND TOWARD ABOVE NORMAL TEMPERATURES ACROSS MOST
AREAS BY THE END OF THE PERIOD.
FOLLOWING A PREDICTED LULL IN ATMOSPHERIC RIVER ACTIVITY LATE IN WEEK-1,
PRECIPITATION CHANCES ARE FORECAST TO INCREASE ON DAY-8 (NOV 9), WITH BOTH THE
ECMWF AND GEFS ENSEMBLES DEPICTING AT LEAST A 50 PERCENT CHANCE OF INTEGRATED
VAPOR TRANSPORT (IVT) EXCEEDING 250 KG/M/S. GIVEN GOOD SUPPORT IN THE PETS
INDICATING AT LEAST A 20 PERCENT CHANCE OF 3-DAY AMOUNTS EXCEEDING THE 85TH
PERCENTILE WITH SIMILAR CHANCES FOR 1 TO 1.5 INCHES OVER PARTS OF THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA, A SLIGHT RISK OF HEAVY PRECIPITATION IS
POSTED FOR NOV 9-13 FOR THESE AREAS. A SLIGHT RISK OF HIGH WINDS ALSO REMAINS
POSTED FOR THIS TIME FRAME FOR COASTAL AREAS BASED ON PETS ALSO INDICATING
INCREASED CHANCES FOR WIND SPEEDS EXCEEDING THE 85TH PERCENTILE. THE EXCESS IN
MOISTURE IS LIKELY TO PRODUCE ACCUMULATING SNOWFALL IN THE HIGHER ELEVATIONS OF
THE CASCADES AND PORTIONS OF THE NORTHERN ROCKIES, THOUGH TOTALS APPEAR
UNLIKELY TO REACH HAZARD THRESHOLDS.
TIED TO THE ANOMALOUS RIDGING FAVORED FURTHER SOUTH, CONDITIONS ARE EXPECTED TO
REMAIN ANOMALOUSLY HOT AND DRY OVER SOUTHERN CALIFORNIA, THE SOUTHWEST, AND
LOWER FOUR CORNERS. WITH MODELS FAVORING MEAN SURFACE HIGH PRESSURE OVER THE
WESTERN GREAT BASIN, THERE IS AN INCREASED POTENTIAL FOR EPISODES OF SANTA ANA
WINDS OVER SOUTHERN CALIFORNIA, THEREFORE A SLIGHT RISK OF HIGH WINDS IS
POSTED FOR NOV 9-10. THIS SURFACE HIGH IS FORECAST TO MOVE EASTWARD BY THE
MIDDLE OF WEEK-2 AS TROUGHING MOVES CLOSER TO THE WEST COAST. HOWEVER, THERE
ARE INDICATIONS IN THE MODELS THAT SURFACE HIGH PRESSURE MAY RETURN TO THE
GREAT BASIN BY THE SECOND HALF OF THE PERIOD. THIS EVOLUTION WILL BE MONITORED
FOR POSSIBLE RE-INTRODUCTION OF THE HAZARD LATER IN WEEK-2.
MID-LEVEL TROUGHING FORECAST OVER THE NORTHEAST PACIFIC TO THE SOUTH OF
MAINLAND ALASKA GENERALLY FAVORS INCREASED ONSHORE FLOW AND SUBSEQUENT ROUNDS
OF HEAVY PRECIPITATION AND HIGH WINDS ACROSS THE SOUTHERN COAST OF THE MAINLAND
AND SOUTHEAST ALASKA. HOWEVER, PRECIPITATION AMOUNTS AND WIND SPEEDS ARE NOT
FORECAST TO REACH HAZARDS THRESHOLDS. TEMPERATURES ARE GENERALLY FORECAST TO BE
ABOVE-NORMAL OVER MOST AREAS, WITH CLOSER TO NORMAL TEMPERATURES FAVORED FOR
THE WESTERN MAINLAND AND ALEUTIANS.
FORECASTER: THOMAS COLLOW
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