699
FXUS21 KWNC 242001
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 24 2023
SYNOPSIS: MID-LEVEL LOW PRESSURE IS ANTICIPATED ACROSS MUCH OF THE CENTRAL AND
EASTERN CONTIGUOUS U.S. (CONUS) DURING WEEK-2. ARCTIC AIR ORIGINATING FROM
SIBERIA IS PREDICTED TO MOVE ACROSS MUCH OF THE CONUS, WITH THE BRUNT OF THE
COLD AIR EXPECTED EAST OF THE CONTINENTAL DIVIDE. SURFACE LOW PRESSURE SOUTH OF
THE ALEUTIANS IS EXPECTED TO LEAD TO THE ESTABLISHMENT OF 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 FOR MOST OF THE GREAT PLAINS
AND MISSISSIPPI VALLEY, GREAT LAKES REGION, OHIO AND TENNESSEE VALLEYS, MOST OF
THE APPALACHIANS, AND MUCH OF THE ATLANTIC PIEDMONT REGION, WED-THU, NOV 1-2.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FROM THE CONTINENTAL DIVIDE
EASTWARD ACROSS THE MISSISSIPPI VALLEY TO THE EAST COAST (INCLUDING NORTHERN
FLORIDA), WED-THU, NOV 1-2.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND PARTS OF
NORTHERN CALIFORNIA, WED-SUN, NOV 1-5.
DETAILED SUMMARY
FOR FRIDAY OCTOBER 27 - TUESDAY OCTOBER 31:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY NOVEMBER 01 - TUESDAY NOVEMBER 07: 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
CONUS, WITH THE CORE OF THE ANOMALOUSLY COLD AIR ANTICIPATED OVER THE
NORTH-CENTRAL STATES. SUBFREEZING MINIMUM TEMPERATURES ARE FORECAST FOR MOST
AREAS EAST OF THE ROCKIES, WITH THE EXCEPTIONS BEING NEAR THE GULF AND
SOUTHEAST COASTS, SIGNIFYING THE END OF THE GROWING SEASON FOR MANY AREAS.
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 CHANCE (20%) OF MUCH
BELOW-NORMAL TEMPERATURES EXTENDS FROM THE CONTINENTAL DIVIDE EASTWARD ACROSS
THE MISSISSIPPI VALLEY TO THE EAST COAST (INCLUDING NORTHERN FLORIDA), NOV 1-2,
BASED ON TEMPERATURES FROM THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOL
(PET). A MODERATE CHANCE (40%) OF MUCH BELOW-NORMAL TEMPERATURES IS HIGHLIGHTED
FOR MUCH OF THE SAME AREA, EXCLUDING MOST OF TEXAS, THE GULF COAST STATES, AND
MUCH OF THE ATLANTIC COASTAL PLAIN, NOV 1-2. 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. DANGEROUSLY COLD CONDITIONS ARE PREDICTED
EARLY IN THE WEEK-2 PERIOD FOR THE NORTHERN HIGH PLAINS, WHERE OVERNIGHT
TEMPERATURES COULD DROP BELOW ZERO DEGREES F, RESULTING IN NEAR-RECORD
TEMPERATURES. NOT ONLY IS THIS COLD WEATHER HAZARDOUS FOR PEOPLE AND LIVESTOCK,
BUT ALSO FOR THE WINTER WHEAT CROP, WHICH TYPICALLY SUSTAINS DAMAGE ONCE THE
TEMPERATURE FALLS TO ABOUT 15 DEGREES F OR COLDER. HOWEVER, ACCUMULATING
SNOWFALL FAVORED DURING THE NEXT COUPLE OF DAYS SHOULD PROVIDE THE WHEAT CROP
WITH INSULATION AGAINST THE ARCTIC COLD IN THIS REGION. FARTHER SOUTH, THE
ECMWF PET DEPICTS AT LEAST A 20% CHANCE OF A HARD FREEZE (28 DEG F OR COLDER)
ACROSS THE NORTHERN HALF OF TEXAS DURING NOV 1-2, THOUGH THE GEFS IS
SIGNIFICANTLY LESS AGGRESSIVE WITH THE COLD TEMPERATURES IN TEXAS.
SURFACE LOW PRESSURE SOUTH OF THE ALEUTIAN ARCHIPELAGO SUPPORTS ONSHORE FLOW
ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, NOV 1-5. THE ECMWF AND
GFS ENSEMBLES SHOW ENHANCED INTEGRATED VAPOR TRANSPORT (IVT) VALUES EXCEEDING
250 KG/M/S DURING THIS PERIOD, CONSISTENT WITH THE EXPECTED ARRIVAL OF HEAVY
PRECIPITATION. A SLIGHT CHANCE (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.
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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