240
FXUS21 KWNC 281828
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 28 2024
SYNOPSIS: A FRONTAL BOUNDARY NEAR THE MIDDLE OF THE CONTIGUOUS UNITED STATES
(CONUS) MAY SERVE AS A FOCUS FOR HEAVY PRECIPITATION EARLY IN WEEK-2 FROM THE
SOUTHERN PLAINS THROUGH MUCH OF THE MISSISSIPPI VALLEY BEFORE DRIFTING EASTWARD
AND WEAKENING. SURFACE HIGH PRESSURE BEHIND THIS SYSTEM IS EXPECTED TO PUSH
COLDER AIR SOUTHWARD, CREATING THE POTENTIAL FOR SIGNIFICANT SNOWFALL OVER
PARTS OF THE CENTRAL AND SOUTHERN ROCKIES AND THE ADJACENT HIGH PLAINS. THE
PRESSURE GRADIENT BETWEEN THE SURFACE HIGH PRESSURE AND LOWER PRESSURES FARTHER
EAST ALONG THE FRONT COULD PRODUCE HIGH WINDS OVER PARTS OF THE EASTERN ROCKIES
AND PLAINS. MEANWHILE, A POTENT STORM SYSTEM MAY BRING HEAVY PRECIPITATION AND
HIGH WINDS TO THE SOUTHERN TIER OF ALASKA, WITH WINDY CONDITIONS POSSIBLY
EXTENDING WESTWARD ACROSS THE ALEUTIANS.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION IN PORTIONS OF THE GREAT PLAINS AND
MISSISSIPPI VALLEY,
TUE-WED, NOV 5-6.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE EASTERN ROCKIES AND GREAT PLAINS,
TUE-WED, NOV 5-6.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES,
TUE-WED, NOV 5-6.
SLIGHT RISK OF HEAVY PRECIPITATION IN SOUTH-CENTRAL AND SOUTHEASTERN ALASKA,
TUE-THU, NOV 5-7.
SLIGHT RISK OF HIGH WINDS FOR SOUTHERN ALASKA, INCLUDING SOUTHWESTERN ALASKA
AND THE ALEUTIANS, TUE-THU, NOV 5-7.
DETAILED SUMMARY
FOR THURSDAY OCTOBER 31 - MONDAY NOVEMBER 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY NOVEMBER 05 - MONDAY NOVEMBER 11: AS WEEK-2 BEGINS, A MID-LEVEL
TROUGH SHOULD BE DRAPED ACROSS THE ROCKIES WITH MID-LEVEL RIDGING FARTHER EAST
OVER THE EASTERN CONUS. EARLY IN WEEK-2, THE TROUGH IS EXPECTED TO DRIFT
EASTWARD AND DE-AMPLIFY. THIS SET-UP SHOULD ESTABLISH A SIGNIFICANT FRONTAL
BOUNDARY OVER OR NEAR THE PLAINS WHICH COULD SERVE AS A FOCUS FOR HEAVY
PRECIPITATION. THIS STORMINESS SHOULD BE ONGOING AS WEEK-2 BEGINS, WITH
ACTIVITY SLOWLY DIMINISHING AS THE MID-LEVEL PATTERN DE-AMPLIFIES AND THE
FRONTAL BOUNDARY WEAKENS DURING THE FIRST TWO DAYS OF THE PERIOD. SOME MODELS -
ESPECIALLY THE 0Z EUROPEAN OPERATIONAL MODEL - MAINTAIN A STRONGER MID-LEVEL
TROUGH THAT IS SLOWER TO TRAVEL EAST, WHICH WOULD PROLONG OR RENEW HEAVY
PRECIPITATION IN THE CENTRAL CONUS, BUT THIS IS NOT THE FAVORED SOLUTION AT
THIS TIME. THE PROBABILISTIC EXTREMES TOOLS (PETS) FOR THE EUROPEAN ENSEMBLES
AND THE GEFS SHOW A BETTER THAN 40 PERCENT CHANCE FOR PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE EARLY IN WEEK-2 IN WESTERN TEXAS AND ADJACENT NEW
MEXICO, WITH THE EUROPEAN PET STRETCHING 40 PERCENT CHANCES ACROSS A BROADER
AREA COVERING MUCH OF THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL AND
SOUTHERN PLAINS, AND THE ADJACENT MISSISSIPPI VALLEY. THE POTENTIAL FOR
ABSOLUTE TOTALS EXCEEDING AN INCH, HOWEVER, ARE ONLY INDICATED FROM THE CENTRAL
PLAINS EASTWARD THROUGH PARTS OF THE MISSISSIPPI VALLEY, WHERE ODDS FOR
PRECIPITATION TO REACH THE 85TH PERCENTILE ARE RELATIVELY LOW. FOR THESE
REASONS, ONLY A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED, NOV 5-6. HIGH
WINDS ARE ALSO POSSIBLE ON THE BACKSIDE OF THE FRONTAL BOUNDARY, SUPPORTING A
SLIGHT RISK FOR HIGH WINDS FOR EASTERN PORTIONS OF THE ROCKIES AND GREAT PLAINS
FOR THE SAME TIMEFRAME.
MANY OF THE TOOLS PLACE A STRONG MID-LEVEL VORTICITY MAXIMUM OVER THE SOUTHWEST
ALONG THE MID-LEVEL TROUGH. THE GEFS MEAN IS STRONGEST WITH THIS FEATURE, WHILE
THE EUROPEAN ENSEMBLE MEAN SHOWS IT RELATIVELY WEAK. THIS IS IN OPPOSITION TO
THE OPERATIONAL EUROPEAN, WHICH SHOWS A STRONG PIECE OF VORTICITY THAT IS
REINFORCED BRIEFLY AROUND THE MIDDLE OF WEEK-2. IN EITHER CASE, THIS WOULD
SERVE TO DRAW MOISTURE WESTWARD FROM THE FRONTAL BOUNDARY INTO AN AREA WHERE
HIGH SURFACE PRESSURE TO THE NORTH IS BRINGING IN COLDER AIR. THIS SET-UP IS
FAVORABLE FOR MODERATE TO HEAVY SNOW OVER PORTIONS OF THE CENTRAL AND SOUTHERN
ROCKIES AND ADJACENT HIGH PLAINS. SOME MEMBERS OF THE EUROPEAN ENSEMBLES AND
GEFS IMPLY A HALF-FOOT OR MORE OF SNOW COULD FALL ON SOME LOCATIONS IN THE
HIGHER ELEVATIONS OF COLORADO WHILE THE GEFS PET FOCUSES THE BEST ODDS FOR
HEAVY SNOW A LITTLE FARTHER SOUTH, FROM SOUTHERN COLORADO THROUGH MOST OF
CENTRAL AND EASTERN NEW MEXICO. A SLIGHT RISK FOR HEAVY SNOWFALL IS POSTED FOR
AREAS AT RISK ACCORDING TO EITHER THE GEFS PET OR EUROPEAN ENSEMBLE OUTPUT,
EXTENDING FROM SOUTHERN WYOMING THROUGH MOST OF COLORADO AND EASTERN NEW MEXICO
FOR NOV 5-6. IF THE MID-LEVEL TROUGH IS STRONGER AND/OR SLOWER TO WEAKEN AND
DRIFT EAST, OR IF A SECONDARY PIECE OF VORTICITY REAMPLIFIES THE FEATURE, HEAVY
SNOW COULD AFFECT A LARGER AREA, OR EXTEND BEYOND THE FIRST TWO DAYS OF THE
PERIOD, BUT THIS IS NOT THE PREFERRED SOLUTION AT THIS TIME, AS DESCRIBED ABOVE.
STRONG MID-LEVEL LOW PRESSURE IS EXPECTED OVER THE SOUTHEASTERN BERING SEA AT
THE START OF WEEK-2, WITH A MINIMUM 500-HPA HEIGHT OF 512 TO 516 DM. MEANWHILE,
A SIGNIFICANT MID-LEVEL RIDGE IS EXPECTED FARTHER EAST, WITH AN AXIS EXTENDING
FROM THE NORTHEASTERN NORTH PACIFIC THROUGH SOUTHEASTERN ALASKA AND INTO
NORTHWESTERN CANADA. THIS WOULD ESTABLISH A STRONG, AMPLIFIED JET OF
CYCLONICALLY-CURVED MID-LEVEL FLOW PUSHING INTO SOUTHERN ALASKA, WITH A POTENT
SURFACE STORM SYSTEM LOCATED OVER OR NEAR SOUTHERN ALASKA. THIS SET-UP HAS THE
POTENTIAL TO BRING UNUSUALLY STORMY WEATHER INTO THE SOUTHERN TIER OF ALASKA.
HEAVY PRECIPITATION WOULD COVER SOUTH-CENTRAL AND SOUTHEASTERN ALASKA NEAR AND
AHEAD OF THE SURFACE LOW PRESSURE CENTER, WHILE HIGH WINDS COULD EXTEND FARTHER
WEST THROUGH MUCH OF THE ALEUTIANS DUE TO THE SURFACE PRESSURE GRADIENT BETWEEN
THE AFOREMENTIONED STORM AND HIGHER SURFACE PRESSURE TO THE NORTHWEST. DESPITE
THIS FAIRLY ROBUST SET-UP, MODEL OUTPUT AND THE PETS SHOW RELATIVELY LOW
CHANCES THAT CONDITIONS WOULD REACH HAZARDS THRESHOLDS, SO ONLY SLIGHT RISKS
FOR HEAVY PRECIPITATION AND HIGH WINDS ARE POSTED, NOV 5-7.
VERY DRY CONDITIONS HAVE PREVAILED ACROSS THE SOUTHEASTERN CONUS, THE
MID-ATLANTIC REGION, AND PORTIONS OF THE NORTHEAST FOR THE PAST FEW WEEKS.
SIGNS OF SURFACE MOISTURE STRESS HAVE BEEN INCREASING IN THESE REGIONS, AND
SHOWN BY THE U.S. DROUGHT MONITOR, BUT RAPID-ONSET DROUGHT IS NOT ANTICIPATED
DUE TO AUTUMNAL TEMPERATURES AND LOWER MOISTURE DEMAND COMPARED TO SUMMER.
A TROPICAL CYCLONE MAY FORM IN THE EASTERN NORTH PACIFIC LATE WEEK-1. THIS
SYSTEM IS NOT EXPECTED TO BECOME A STRONG HURRICANE, BUT IT HAS THE POTENTIAL
TO BRING SOME GUSTY WINDS, HIGH SURF, AND HEAVY PRECIPITATION TO PORTIONS OF
HAWAII IF IT TRACKS NEAR THE STATE. NO HAZARDS ARE POSTED IN ASSOCIATION WITH
THIS SYSTEM, BUT IT WILL CONTINUE TO BE MONITORED.
FORECASTER: RICH TINKER
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