989
FXUS21 KWNC 251817
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 25 2023
SYNOPSIS: MID-LEVEL LOW PRESSURE IS ANTICIPATED ACROSS MUCH OF THE CENTRAL AND
EASTERN CONTIGUOUS U.S. (CONUS) DURING WEEK-2. JUST BEFORE OR AT THE START OF
THE FORECAST PERIOD, AN ARCTIC OUTBREAK IS PREDICTED TO BE AT ITS PEAK ACROSS
MUCH OF THE CONUS EAST OF THE ROCKIES, FOLLOWED BY A FAIRLY RAPID MODERATION IN
SURFACE TEMPERATURES. SURFACE LOW PRESSURE SOUTH OF ALASKA IS EXPECTED TO BRING
ONSHORE FLOW ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA INCREASING
THE CHANCES FOR HEAVY PRECIPITATION ACROSS THIS REGION.
HAZARDS
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FROM THE SOUTHERN OHIO AND
TENNESSEE VALLEYS EASTWARD ACROSS APPROXIMATELY THE SOUTHERN HALF OF THE
APPALACHIANS AND ADJACENT PIEDMONT REGION, THU, NOV 2.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FROM MUCH OF THE GREAT PLAINS AND
MISSISSIPPI VALLEY EASTWARD TO THE ATLANTIC COAST FROM ABOUT CENTRAL NEW JERSEY
TO THE FLORIDA PANHANDLE, THU-FRI, NOV 2-3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND PARTS OF
NORTHERN CALIFORNIA, THU-MON, NOV 2-6.
DETAILED SUMMARY
FOR SATURDAY OCTOBER 28 - WEDNESDAY NOVEMBER 01:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY NOVEMBER 02 - WEDNESDAY NOVEMBER 08: A MID-LEVEL TROUGH IS
PREDICTED ACROSS MUCH OF THE CENTRAL AND EASTERN CONTIGUOUS U.S. (CONUS) DURING
WEEK-2. THIS FLOW PATTERN SUPPORTS THE DELIVERY OF ARCTIC AIR TO MUCH OF THE
COUNTRY EAST OF THE ROCKIES, THOUGH THE PEAK OF THIS EVENT IS EXPECTED JUST
BEFORE OR AT THE BEGINNING OF THIS FORECAST PERIOD. SUBFREEZING MINIMUM
TEMPERATURES ARE FORECAST FOR MOST AREAS EAST OF THE ROCKIES, SIGNIFYING THE
END OF THE GROWING SEASON FOR MANY AREAS. THE EXCEPTIONS INCLUDE NEAR THE GULF
AND SOUTHEAST COASTS, AND POSSIBLY THE IMMEDIATE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND COASTS. TODAY’S ENSEMBLE MODEL GUIDANCE INDICATES A FASTER TRANSITION
OF AN ARCTIC OUTBREAK TO A MODERATING TREND COMPARED TO YESTERDAY’S SOLUTIONS,
AND TODAY’S ECMWF MODEL IS MORE BULLISH ON THE MAGNITUDE AND SPATIAL EXTENT OF
THE ANOMALOUS COLD COMPARED TO THE GEFS.
A SLIGHT RISK (20%) OF MUCH BELOW-NORMAL TEMPERATURES EXTENDS FROM MUCH OF THE
GREAT PLAINS AND MISSISSIPPI VALLEY EASTWARD TO THE ATLANTIC COAST FROM ABOUT
CENTRAL NEW JERSEY TO THE FLORIDA PANHANDLE, THU-FRI, NOV 2-3. THIS IS BASED ON
TEMPERATURES FROM THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOL (PET), AND
CONSIDERATION OF THE FORECAST MOVEMENT OF A SURFACE HIGH ACROSS THE SOUTHEAST.
A MODERATE RISK (40%) OF MUCH BELOW-NORMAL TEMPERATURES IS HIGHLIGHTED FROM THE
SOUTHERN OHIO AND TENNESSEE VALLEYS EASTWARD ACROSS APPROXIMATELY THE SOUTHERN
HALF OF THE APPALACHIANS AND ADJACENT PIEDMONT REGION, THU, NOV 2. THE MODERATE
RISK AREA WAS DRAWN BASED ON THE PET TOOLS, DAY 7 TEMPERATURE GUIDANCE FROM THE
WEATHER PREDICTION CENTER, AND ON FIRST FREEZE AND VEGETATION SUSCEPTIBILITY
MAPS FROM THE MIDWESTERN REGIONAL CLIMATE CENTER. HAZARDOUS COLD IS STILL
ANTICIPATED ACROSS THE NORTHERN PLAINS WHERE, ACCORDING TO THE MORE BULLISH
ECMWF PET, MINIMUM TEMPERATURES MAY FALL BELOW THE 10TH CLIMATOLOGICAL
PERCENTILE AND APPROACH 0 DEGREES F, THOUGH THE MILDER GEFS PET PREDICTS
MINIMUM TEMPERATURES WILL BE ABOUT 10-15 DEGREES WARMER.
SURFACE LOW PRESSURE SOUTH OF ALASKA SUPPORTS INCREASED ONSHORE FLOW ACROSS THE
PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, NOV 2-6. THE ECMWF AND GFS ENSEMBLES
SHOW INTEGRATED VAPOR TRANSPORT (IVT) VALUES EXCEEDING 250 KG/M/S DURING THIS
PERIOD, CONSISTENT WITH THE PREDICTED ARRIVAL OF HEAVY PRECIPITATION. A SLIGHT
RISK (20%) OF HEAVY PRECIPITATION (3-DAY TOTALS OF 1.5 INCHES (LOCALLY UP TO 2
INCHES) AND IN EXCESS OF THE CLIMATOLOGICAL 85TH PERCENTILE) IS THEREFORE
POSTED FOR THIS REGION.
THE GFS AND ECMWF ENSEMBLE MEANS DEPICT THE ELEVATED POTENTIAL FOR TROPICAL
DEVELOPMENT ACROSS THE CARIBBEAN SEA DURING WEEK-2. SOME OF THIS RAIN COULD
REACH FLORIDA, BUT FORECAST RAW TOTALS (1.0-1.5 INCHES) ARE WELL BELOW
HAZARDOUS THRESHOLDS. A MID-LEVEL TROUGH PREDICTED TO APPROACH THE EAST COAST
OF THE U.S. LATER IN WEEK-2 IS FAVORED TO HELP STEER THE TROPICAL DISTURBANCE
NORTHEASTWARD, KEEPING MOST OF ITS PRECIPITATION OFF THE FLORIDA COAST.
A WEAKENING ANOMALOUS RIDGE ACROSS ALASKA DURING WEEK-2 FAVORS ABOVE-NORMAL
TEMPERATURES FOR MOST OF THE STATE. NO HAZARDS ARE POSTED FOR ALASKA AT THIS
TIME.
FORECASTER: ANTHONY ARTUSA
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