219
FXUS21 KWNC 011905
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT NOVEMBER 01 2024
SYNOPSIS: A MID-LEVEL TROUGH MAY SPIN UP A SURFACE STORM SYSTEM NEAR THE
PACIFIC NORTHWEST, SETTING UP THE POTENTIAL FOR HEAVY PRECIPITATION IN THE
PACIFIC NORTHWEST, WITH HEAVY SNOW POSSIBLE IN PARTS OF THE CASCADES. BOTH THE
FAVORED SURFACE AND MID-LEVEL PATTERN ALSO SUPPORT AN INCREASED RISK OF HIGH
WINDS TO A LARGE AREA INCLUDING THE PACIFIC NORTHWEST, THE NORTHERN
INTERMOUNTAIN WEST, AND THE CENTRAL AND NORTHERN PORTIONS OF THE ROCKIES AND
PLAINS. MEANWHILE, ONE OR MORE STRONG SURFACE LOW PRESSURE SYSTEMS ARE FORECAST
OVER THE GULF OF ALASKA, BRINGING THE POTENTIAL FOR HIGH WINDS TO THE SOUTHERN
TIER OF THE STATE, INCLUDING THE ALEUTIANS.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION IN PORTIONS OF THE PACIFIC NORTHWEST,
SAT-TUE, NOV 9-12.
SLIGHT RISK OF HEAVY SNOW IN PORTIONS OF THE CENTRAL AND NORTHERN CASCADES,
SAT-TUE, NOV 9-12.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE PACIFIC NORTHWEST, NORTHERN
INTERMOUNTAIN WEST, ROCKIES, AND PLAINS, SAT-TUE, NOV 9-12.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN TIER OF ALASKA INCLUDING THE
ALEUTIANS, SAT-MON, NOV 9-11.
DETAILED SUMMARY
FOR MONDAY NOVEMBER 04 - FRIDAY NOVEMBER 08:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY NOVEMBER 09 - FRIDAY NOVEMBER 15: THE SYNOPTIC PICTURE FOR THE
CONTIGUOUS U.S. (CONUS) DURING WEEK-2 IS CHARACTERIZED BY A WEAKENING VORTICITY
MAXIMUM MOVING ACROSS THE ROCKIES INTO WEAK RIDGING OVER THE EASTERN SEABOARD,
AS DEPICTED BY THE ECENS, GEFS, AND CMCE 500-HPA HEIGHT AND ANOMALY SOLUTIONS.
MEANWHILE, A STRONG MID-LEVEL TROUGH ACROSS ALASKA AND ADJACENT AREAS IS
EXPECTED TO EXPAND EASTWARD AND SOUTHEASTWARD DURING THE FIRST PART OF WEEK-2
SOMEWHERE INTO WESTERN NORTH AMERICA AND/OR THE WESTERN NORTH PACIFIC. THERE IS
A LOT OF UNCERTAINTY WITH THE DETAILS OF THIS EVOLVING PATTERN, WITH THE MODELS
DEPICTING A BROAD ARRAY OF POSSIBLE SOLUTIONS. STILL, A STORMY PERIOD IS
POSSIBLE ACROSS THE PACIFIC NORTHWEST FOR THE EARLY AND MIDDLE PART OF WEEK-2,
AND THE THREAT OF HIGH WINDS COVERS A LARGER AREA INCLUDING PORTIONS OF THE
INTERMOUNTAIN WEST, ROCKIES, AND PLAINS. HOWEVER, ONLY SLIGHT RISKS FOR HIGH
WINDS, HEAVY PRECIPITATION, AND HEAVY SNOW ARE POSTED DUE INCONSISTENCIES AMONG
THE TOOLS REGARDING THE DETAILS OF LOCATION, STRENGTH, AND TIMING OF THIS
EVOLVING PATTERN. IN OTHER PARTS OF THE NATION, MILD AND TRANQUIL WEATHER IS
ANTICIPATED UNDER THE INFLUENCE OF A FLAT MID-LEVEL RIDGE OVER THE NORTHERN AND
EASTERN PARTS OF THE CONUS.
DEEP UPPER-LEVEL TROUGHING OVER THE BERING SEA AND GULF OF ALASKA IS DEPICTED
AT THE OUTSET OF WEEK-2 AND PERSISTS THROUGH MOST OF THE FORECAST PERIOD,
GRADUALLY WEAKENING AS THE WEEK PROGRESSES. MODEL SOLUTIONS SHOW ONE OR MORE
STRONG SURFACE LOW PRESSURE SYSTEMS TRACKING THROUGH GULF OF ALASKA, WITH
CENTRAL PRESSURES RANGING FROM 976 MB OVER SOUTHWESTERN ALASKA AT THE START OF
THE PERIOD IN THE OPERATIONAL EUROPEAN MODEL, TO NEAR 985 MB IN THE GULF OF
ALASKA NEAR THE SOUTH-CENTRAL COAST IN THE OPERATIONAL CANADIAN AND CANADIAN
ENSEMBLE MEANS. THERE IS SIGNIFICANT UNCERTAINTY REGARDING THE STRENGTH, TRACK,
AND TIMING OF THE ONE OR MORE STORM SYSTEMS EXPECTED TO AFFECT THE REGION, BUT
AN ELEVATED RISK OF HIGH WINDS IS FAIRLY CONSISTENT ACROSS THE SOUTHERN TIER OF
THE STATE FOR AT LEAST PART OF THE FIRST HALF OF WEEK-2. ANY STORMS THAT FORM
SHOULD BE FAIRLY PROGRESSIVE, HOWEVER, SO THERE IS LESS OF A RISK FOR A
SIGNIFICANT PERIOD OF HEAVY PRECIPITATION RELATIVE TO THE REGION’S CLIMATOLOGY.
FARTHER EAST, THIS LONG-WAVE TROUGH WILL BE IN THE PROCESS OF MOVING OR
EXPANDING TOWARD WESTERN CANADA, THE WESTERN CONUS, AND/OR THE EASTERN NORTH
PACIFIC OCEAN. GUIDANCE GENERALLY AGREES ON THIS PATTERN EVOLUTION, BUT THE
DETAILS OF TIMING, LOCATION, AND STRENGTH ARE HIGHLY UNCERTAIN. THE EUROPEAN
AND CANADIAN ENSEMBLE MEANS PUSH A MODERATE MID-LEVEL TROUGH INTO WESTERN
CANADA AND THE ADJACENT CONUS WHILE THE GEFS MEAN BRINGS A MUCH STRONGER
MID-LEVEL TROUGH TOWARD THE PACIFIC NORTHWEST EARLY IN WEEK-2. MEANWHILE, THE
OPERATIONAL CANADIAN MODEL EJECTS A VORTICITY MAXIMUM OUT OF THE TROUGH THAT
DIVES SOUTHWARD ALONG OR NEAR THE WESTERN CONUS COAST BEFORE MOVING A CUT-OFF
MID-LEVEL LOW INTO THE SOUTHWEST. THIS LATTER EVOLUTION SEEMS UNLIKELY, BUT
HIGHLIGHTS THE BROAD ARRAY OF POTENTIAL SOLUTIONS DEPICTED BY THE TOOLS. STILL,
THERE IS ENOUGH GUIDANCE SHOWING A POTENT SYSTEM BRINGING STORMY WEATHER INTO
THE NORTHWEST TO POST A SLIGHT RISK OF HEAVY PRECIPITATION ACROSS THE REGION,
INCLUDING A SLIGHT RISK OF HEAVY SNOW OVER THE HIGHER ELEVATIONS AND SOME
MOUNTAIN PASSES ACROSS THE CENTRAL AND NORTHERN CASCADES.
ANY POTENT INDIVIDUAL SURFACE LOW PRESSURE SYSTEM COULD GENERATE HEAVY WINDS IN
THE NORTHWEST TO ACCOMPANY ANY HEAVY PRECIPITATION. ON A BROADER SCALE, MOST
MODEL SOLUTIONS SHOW RELATIVELY LOW SURFACE PRESSURES ACROSS SOUTHERN CANADA
AND INTO THE NORTH-CENTRAL CONUS WHILE A MODERATELY STRONG SURFACE HIGH
PRESSURE CENTER SITS OVER THE CENTRAL ROCKIES. THE RESULTING PRESSURE GRADIENT
CREATES THE POTENTIAL FOR HIGH WINDS ACROSS THE NORTHERN INTERMOUNTAIN WEST AND
THE CENTRAL AND NORTHERN SECTIONS OF THE ROCKIES AND PLAINS, IN ADDITION TO THE
PACIFIC NORTHWEST. TO WIT, THIS LARGER AREA IS UNDER A SLIGHT RISK FOR HIGH
WINDS EVEN THOUGH THE RISK OF HEAVY PRECIPITATION IS LIMITED TO A SMALLER AREA
RESTRICTED TO THE PACIFIC NORTHWEST. LATER WEEK-2, THE PRESSURE GRADIENT
RELAXES AND THE MID-LEVEL PATTERN LOOKS TO BEGIN DEAMPLIFYING, ENDING THE RISKS
FOR HIGH WINDS AND HEAVY RAIN OR SNOW.
OCTOBER WAS EXCEPTIONALLY DRY ALONG MUCH OF THE EASTERN SEABOARD, WITH NO
MEASURABLE RAINFALL REPORTED IN NEW YORK CITY, NEWARK AND TRENTON NJ,
PHILADELPHIA PA, WILMINGTON DE, COLUMBIA SC, AND ATLANTA GA AMONG OTHER
LOCATIONS. MOST OF THE ATLANTIC COASTAL PLAINS RECEIVED ONLY A FEW TENTHS OF AN
INCH AT MOST, WHICH PRIMARILY FELL EARLY IN THE MONTH. DESPITE THE EXTREME
SHORT-TERM DRYNESS, NO RISK AREA FOR RAPID-ONSET DROUGHT IS IDENTIFIED DUE TO
CLIMATOLOGICALLY LOWER TEMPERATURES AND THE REDUCED ENVIRONMENTAL AND HUMAN
WATER DEMAND IN MID-AUTUMN AS OPPOSED TO DURING THE SUMMER.
FORECASTER: RICH TINKER
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