610
FXUS21 KWNC 291849
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 29 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 GREAT PLAINS THROUGH MUCH OF THE MISSISSIPPI VALLEY BEFORE DRIFTING
EASTWARD AND WEAKENING. COLD SURFACE HIGH PRESSURE IN THE NORTH-CENTRAL CONUS
IS FORECAST TO INTERACT WITH A MID-LEVEL LOW DEVELOPING IN THE SOUTHWEST TO
CREATE 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 POTENTIALLY MERGING WITH A TROPICAL CYCLONE
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 MISSISSIPPI VALLEY, LOWER
OHIO VALLEY, AND GREAT PLAINS WED-THU, NOV 6-7.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE EASTERN ROCKIES AND GREAT PLAINS,
WED, NOV 6.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES AND
ADJACENT HIGH PLAINS WED-THU, NOV 6-7.
SLIGHT RISK OF HEAVY PRECIPITATION IN SOUTH-CENTRAL AND SOUTHEASTERN ALASKA,
WED-FRI, NOV 6-8.
SLIGHT RISK OF HIGH WINDS FOR SOUTHERN ALASKA, INCLUDING SOUTHWESTERN ALASKA
AND THE ALEUTIANS, WED-FRI, NOV 6-8.
DETAILED SUMMARY
FOR FRIDAY NOVEMBER 01 - TUESDAY NOVEMBER 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY NOVEMBER 06 - TUESDAY NOVEMBER 12: 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 LIFT
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. AS OPPOSED TO
YESTERDAY, MOST MODELS NOW BRING A SECOND PIECE OF VORTICITY SOUTHWARD INTO THE
WESTERN CONUS TROUGH THAT CUTS OFF A MID-LEVEL LOW OVER THE SOUTHWEST. THIS IS
THE FAVORED SOLUTION TODAY, WHICH SHOULD SLOW DOWN THE FRONTAL SYSTEM SOMEWHAT
RELATIVE TO YESTERDAY’S FORECAST AND PROLONG THE THREAT FOR HEAVY
PRECIPITATION. THE PROBABILISTIC EXTREMES TOOLS (PETS) FOR THE EUROPEAN
ENSEMBLES SHOW A BETTER THAN 40 PERCENT CHANCE FOR PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE EARLY IN WEEK-2 IN TEXAS AND ADJACENT NEW MEXICO,
WHILE THE GEFS AND CANADIAN ENSEMBLE PETS ARE LESS ROBUST. BUT THE OPERATIONAL
EUROPEAN AND CANADIAN MODELS, AND TO A LESSER EXTENT THE GFS, SHOW BANDS OF
HEAVY PRECIPITATION - CONSIDERABLY MORE THAN SHOWN BY THE ENSEMBLE MEANS -
PERSISTING OVER PARTS OF THE REGION INTO MID-WEEK. AS A RESULT, THE POTENTIAL
FOR ABSOLUTE TOTALS EXCEEDING AN INCH ARE ONLY DEPICTED IN THE EUROPEAN
ENSEMBLE PET WITH RELATIVELY LOW CHANCES, BUT ONE TO SEVERAL INCHES IS SHOWN IN
SMALLER PARTS OF THE REGION IN THE OPERATIONAL MODELS. FOR THESE REASONS, A
SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED, NOV 6-7. HIGH WINDS ARE ALSO
POSSIBLE ON THE BACKSIDE OF THE FRONTAL BOUNDARY, SUPPORTING A SLIGHT RISK FOR
HIGH WINDS FOR PORTIONS OF THE EASTERN ROCKIES AND THE PLAINS FOR THE FIRST DAY
OF WEEK-2 (NOV 6).
MORE OF THE TOOLS NOW SHOW A STRONG MID-LEVEL VORTICITY MAXIMUM DROPPING INTO
THE SOUTHWEST BEHIND THE ONE LIFTING INTO THE PLAINS EARLY WEEK-2. THE GFS,
OPERATIONAL EUROPEAN, AND OPERATIONAL CANADIAN MODELS ALL SHOW SOME REFLECTION
OF THIS FEATURE, WITH THE GFS LESS AMPLIFIED THAN THE OTHERS. THE EUROPEAN
ENSEMBLE MEAN SHOWS A RELATIVELY WEAK REFLECTION OF THIS FEATURE WHILE THE GEFS
AND CANADIAN ENSEMBLE MEANS DO NOT SHOW A CUT-OFF MID-LEVEL LOW. THIS IMPLIES
THAT, WHILE THE DEVELOPMENT OF A CUT-OFF MID-LEVEL LOW SEEMS MORE LIKELY THAN
IT DID YESTERDAY, THERE IS STILL CONSIDERABLE UNCERTAINTY. BUT EVEN WITH A
SOMEWHAT WEAKER SCENARIO THAN SHOWN IN THE OPERATIONAL MODELS, 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. THE OPERATIONAL EUROPEAN AND CANADIAN MODELS
SHOW SMALL AREAS WHERE OVER A FOOT OF SNOW IS POSSIBLE, BUT THE OPERATIONAL 6Z
GFS BRINGS IN LITTLE OR NO SNOWFALL DESPITE IT SHOWING SOME REFLECTION OF A
CUT-OFF MID-LEVEL LOW IN THE SOUTHWEST. MEANWHILE, THE GEFS PET FOCUSES THE
BEST ODDS FOR HEAVY SNOW A LITTLE FARTHER EAST EXTENDING INTO THE HIGH PLAINS
AS FAR EAST AS THE TEXAS AND OKLAHOMA PANHANDLES. GIVEN ALL THE UNCERTAINTY, A
SLIGHT RISK FOR HEAVY SNOWFALL IS POSTED FOR AREAS AT RISK ACCORDING TO EITHER
THE GEFS PET OR OPERATIONAL EUROPEAN AND CANADIAN MODELS, EXTENDING FROM
SOUTHERN WYOMING THROUGH MOST OF COLORADO AND EASTERN NEW MEXICO, AS FAR WEST
AS EASTERN ARIZONA AND UTAH, AND AS FAR EAST AS THE SOUTHWESTERN GREAT PLAINS
FOR NOV 6-7.
STRONG MID-LEVEL LOW PRESSURE AND ASSOCIATED SURFACE STORM SYSTEM IS EXPECTED
OVER OR NEAR THE ALEUTIANS AT THE START OF WEEK-2. THIS SYSTEM COULD BE
ENHANCED AS THE MID-LEVEL LOW MERGES WITH THE REMNANTS OF TYPHOON KONG-REY
FOLLOWING EXTRATROPICAL TRANSITION. THE 6Z AND 12Z OPERATIONAL GFS RUNS START
WEEK-2 WITH A 950- TO 955-HPA SURFACE LOW OVER THE CENTRAL ALEUTIANS. THE
OPERATIONAL EUROPEAN AND CANADIAN MODELS ARE A BIT WEAKER WITH THIS SYSTEM,
WITH PRESSURES BOTTOMING OUT IN THE LOW 970’S AND TRACKING A LITTLE FARTHER
AWAY FROM THE SOUTHERN ALASKAN COAST. IN ANY CASE, 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, ESPECIALLY IF THE CENTRAL PRESSURE DROPS AS
LOW AS THE OPERATIONAL GFS SHOWS. BUT DUE TO THE UNCERTAINTIES IN THE
DEVELOPMENT AND TRACK OF THE STORM SYSTEM, INCLUDING ITS POTENTIAL INTERACTION
WITH THE REMNANTS OF TYPHOON KONG-REY, ONLY SLIGHT RISKS FOR HEAVY
PRECIPITATION AND HIGH WINDS ARE POSTED NOV 6-8. WITH MOST MODELS SHOWING A
SLOWER-MOVING SYSTEM THAN YESTERDAY, THIS HAZARD HAS BEEN EXTENDED FOR AN
ADDITIONAL DAY RELATIVE TO YESTERDAY’S FORECAST. IN ADDITION, THERE ARE SIGNS
THAT THIS STORM COULD BE FOLLOWED BY ADDITIONAL STORM SYSTEMS, WHICH WOULD
EXTEND THE RISK FOR AN EVEN LONGER PERIOD.
VERY DRY CONDITIONS HAVE PREVAILED ACROSS THE SOUTHEASTERN CONUS, THE
MID-ATLANTIC REGION, AND PORTIONS OF THE NORTHEAST FOR THE PAST FEW WEEKS. IN
PHILADELPHIA, PA, OCTOBER 29 IS THE 31ST CONSECUTIVE DAY WITHOUT MEASURABLE
PRECIPITATION, BESTING THE PRIOR RECORD OF 29 DAYS ESTABLISHED IN 1874. SIGNS
OF SURFACE MOISTURE STRESS HAVE BEEN INCREASING, AS REFLECTED IN 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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