669
FXUS21 KWNC 231946
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 23 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 IN
WESTERN CANADA 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
HIGH RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE NORTHERN GREAT PLAINS,
TUE-WED, OCT 31-NOV 1.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MOST OF THE GREAT PLAINS,
MISSISSIPPI VALLEY FROM MINNESOTA TO NORTHERN MISSOURI, AND THE WESTERN GREAT
LAKES REGION, TUE-WED, OCT 31-NOV 1.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FROM THE NORTHERN INTERMOUNTAIN
SOUTHWARD TO THE FOUR CORNERS, TUE, OCT 31.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES EXTENDING FROM THE CONTINENTAL
DIVIDE EASTWARD ACROSS MOST OF THE GREAT PLAINS AND MISSISSIPPI VALLEY, GREAT
LAKES REGION, NORTHERN OHIO VALLEY, AND MUCH OF THE INTERIOR NORTHEAST, OCT
31-NOV 3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND PARTS OF
NORTHERN CALIFORNIA, WED-SAT, NOV 1-4.
DETAILED SUMMARY
FOR THURSDAY OCTOBER 26 - MONDAY OCTOBER 30:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY OCTOBER 31 - MONDAY NOVEMBER 06: 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. THE ECMWF PROBABILISTIC EXTREMES TOOL (PET) IS SIGNIFICANTLY COLDER
TODAY THAN THE GEFS PET, BOTH IN TERMS OF THE MAGNITUDE OF THE COLD, AND ITS
SPATIAL EXTENT. THE ECMWF PET IS FAVORED TODAY OVER THE GEFS, ALTHOUGH THE GEFS
SOLUTION ALSO INDICATES THE POTENTIAL FOR A SIGNIFICANT ARCTIC OUTBREAK. A HIGH
RISK (60% CHANCE) OF MUCH BELOW-NORMAL TEMPERATURES IS HIGHLIGHTED FOR THE
NORTHERN GREAT PLAINS, OCT 31-NOV 1. THE CENTRAL PORTION OF THIS AREA COULD
EXPERIENCE MINIMUM TEMPERATURES WITHIN THE LOWEST ONE OR TWO PERCENT OF THE
HISTORICAL TEMPERATURE DISTRIBUTION (THEREBY SUGGESTING RECORD OR NEAR-RECORD
VALUES), AND TEMPERATURES FALLING TO BELOW ZERO F. NOT ONLY IS THIS DANGEROUS
COLD 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. A
MODERATE CHANCE (40%) OF MUCH BELOW-NORMAL TEMPERATURES IS DEPICTED FOR MOST OF
THE GREAT PLAINS, MISSISSIPPI VALLEY FROM MINNESOTA TO NORTHERN MISSOURI, AND
THE WESTERN GREAT LAKES REGION, OCT 31-NOV 1. THE ECMWF PET FORECASTS AT LEAST
A 20% CHANCE OF TEMPERATURES FALLING TO 32 DEG F OR COLDER FOR APPROXIMATELY
THE NORTHWESTERN HALF OF TEXAS, WITH A HARD FREEZE (28 DEG F OR COLDER) FOR THE
ENTIRE TEXAS PANHANDLE. A SLIGHT CHANCE (20%) OF MUCH BELOW-NORMAL TEMPERATURES
EXTENDS FROM THE CONTINENTAL DIVIDE EASTWARD ACROSS MOST OF THE GREAT PLAINS
AND MISSISSIPPI VALLEY, GREAT LAKES REGION, NORTHERN OHIO VALLEY, AND MUCH OF
THE INTERIOR NORTHEAST, OCT 31-NOV 3, WHERE THERE IS SUPPORT FROM THE PETS
INDICATING INCREASED CHANCES FOR MINIMUM TEMPERATURES FALLING BELOW THE 15TH
PERCENTILE. INCREASED CHANCES FOR MUCH BELOW NORMAL TEMPERATURES ARE ALSO
PREDICTED OVER MANY AREAS WEST OF THE CONTINENTAL DIVIDE, ESPECIALLY THE
EASTERN INTERMOUNTAIN REGION, OCT 31. HOWEVER, THIS EVENT APPEARS TO BE VERY
BRIEF BASED ON PET GUIDANCE.
SURFACE LOW PRESSURE SOUTH OF THE ALEUTIAN ARCHIPELAGO SUPPORTS ONSHORE FLOW
ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, NOV 1-4. 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 AND IN EXCESS OF THE CLIMATOLOGICAL 85TH PERCENTILE) IS THEREFORE
POSTED FOR THIS REGION.
ANOMALOUS RIDGING ACROSS ALASKA DURING WEEK-2 FAVORS ABOVE-NORMAL TEMPERATURES
FOR PRACTICALLY THE ENTIRE STATE. NO HAZARDS ARE POSTED FOR ALASKA AT THIS TIME.
FORECASTER: ANTHONY ARTUSA
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