737
FXUS21 KWNC 192019
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 19 2024
SYNOPSIS: MID-LEVEL LOW PRESSURE PREDICTED OVER THE CONTIGUOUS U.S. (CONUS)
SUPPORTS INCREASED CHANCES FOR HAZARDOUS COLD ACROSS THE NORTH-CENTRAL CONUS
AND UNSETTLED WEATHER ACROSS THE EASTERN CONUS DURING THE BUSY THANKSGIVING
TRAVEL SEASON. MODEL GUIDANCE AND TOOLS SHOW INCREASED SIGNALS FOR MULTIPLE
HAZARDS LEADING TO MODERATE RISKS (40-60%) OF HEAVY PRECIPITATION FOR PARTS OF
THE TENNESSEE AND OHIO VALLEYS AND MUCH OF THE CENTRAL APPALACHIANS, HAZARDOUS
COLD ACROSS THE NORTHERN PLAINS, AND HIGH EPISODIC WINDS ACROSS PORTIONS OF THE
EASTERN THIRD OF THE CONUS, LOWER MISSISSIPPI VALLEY, AND COASTAL TEXAS.
BROADER AREAS OF SLIGHT RISKS ARE HIGHLIGHTED FOR THESE HAZARDS IN ADDITION TO
A SLIGHT RISK OF HEAVY SNOW ACROSS PARTS OF THE GREAT LAKES AND NORTHEAST.
SURFACE LOW PRESSURE OVER THE GULF OF ALASKA COMBINED WITH ADJACENT SURFACE
HIGH PRESSURE ACROSS MUCH OF THE MAINLAND, YUKON, AND BRITISH COLUMBIA
INCREASES CHANCES FOR HIGH GAP WINDS ACROSS SOUTHEASTERN ALASKA TOWARDS THE
LATTER PART OF WEEK-2.
HAZARDS
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE NORTHERN
PLAINS, WED-SAT, NOV 27-NOV 30.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE NORTHERN
PLAINS AND UPPER MISSISSIPPI VALLEY, WED-TUE, NOV 27-DEC 3.
MODERATE RISK OF HEAVY PRECIPITATION FOR PARTS OF THE TENNESSEE AND OHIO
VALLEYS AND MUCH OF THE CENTRAL APPALACHIANS, WED-THU, NOV 27-28.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE NORTHEAST, MID-ATLANTIC,
OHIO, TENNESSEE, AND MIDDLE AND LOWER MISSISSIPPI VALLEYS, AND APPALACHIANS,
WED-FRI, NOV 27-29.
SLIGHT RISK OF PERIODS OF HEAVY LAKE EFFECT SNOW ACROSS PARTS OF THE GREAT
LAKES AND NORTHEAST, WED-TUE, NOV 27-DEC 3.
MODERATE RISK OF EPISODIC HIGH WINDS ACROSS THE OHIO AND TENNESSEE VALLEYS,
APPALACHIANS, MID-ATLANTIC, AND SOUTHEAST, WED-FRI, NOV 27-29.
SLIGHT RISK OF EPISODIC HIGH WINDS ACROSS PORTIONS OF THE EASTERN THIRD OF THE
CONUS, LOWER MISSISSIPPI VALLEY, AND COASTAL TEXAS, WED-FRI, NOV 27-29.
DETAILED SUMMARY
FOR FRIDAY NOVEMBER 22 - TUESDAY NOVEMBER 26:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY NOVEMBER 27 - TUESDAY DECEMBER 03: THE GEFS AND ECENS ENSEMBLE
MEANS INDICATE AN AMPLIFIED TROUGH STRETCHING ACROSS THE EASTERN TWO-THIRDS OF
THE CONUS DURING WEEK-2, INITIALLY CENTERED OVER THE CENTRAL CONUS PROGRESSING
EASTWARD WITH TIME. THE CMCE ENSEMBLE MEAN IS AN OUTLIER, INDICATING A MUCH
WEAKER PATTERN COMPARED TO THE OTHER MODELS. THE FORECAST AMPLIFIED PATTERN
TRANSLATES TO INCREASED CHANCES, COMPARED TO YESTERDAY, FOR HAZARDOUS WEATHER
CONDITIONS DURING THE BUSY THANKSGIVING TRAVEL PERIOD.
SURFACE HIGH PRESSURE IS PREDICTED TO SINK SOUTHWARD FROM WESTERN CANADA INTO
THE CENTRAL CONUS AND INTERIOR WEST AT THE ONSET OF WEEK-2, BRINGING COLD
ARCTIC AIR INTO THE REGION. A SLIGHT RISK (20-40% CHANCE) OF MUCH BELOW NORMAL
TEMPERATURES IS DESIGNATED FOR PARTS OF THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY THROUGHOUT WEEK-2. A MODERATE RISK (40-60% CHANCE) IS
INCLUDED IN TODAY’S OUTLOOK FOR THE NORTHERN PLAINS, WHERE THE PROBABILISTIC
EXTREMES TOOLS (PETS) INDICATE AT LEAST A 20% CHANCE OF MINIMUM TEMPERATURES
FALLING TO THE LOWEST 15TH PERCENTILE CLIMATOLOGICALLY AND -10 DEG F, WITH WIND
CHILL TEMPERATURES POTENTIALLY BEING EVEN LOWER.
SURFACE LOW PRESSURE AND ASSOCIATED FRONTS ARE PREDICTED TO TRACK FROM THE
CENTRAL CONUS TO THE GREAT LAKES AHEAD OF THE MID-LEVEL TROUGH FROM THE END OF
WEEK-1 INTO THE BEGINNING OF WEEK-2. MULTIPLE ENSEMBLE MEANS INDICATE STRONGER
SIGNALS FOR HEAVY PRECIPITATION AND HIGH WINDS ACROSS PARTS OF THE EAST,
ALTHOUGH THERE ARE STILL MODEL DIFFERENCES ACROSS VARIOUS MODEL RUNS INCLUDING
DETERMINISTIC MODELS REGARDING THE DETAILS OF THE TIMING AND EVOLUTION OF THESE
FEATURES. THERE IS UNCERTAINTY REGARDING HOW PROGRESSIVE THE PATTERN WILL BE,
WHICH WOULD THE TIMING AND IMPACT OF THE HAZARDS BY THE WEEK-2 PERIOD. A
MODERATE RISK (40-60% CHANCE) OF HEAVY PRECIPITATION IS DESIGNATED FOR PARTS OF
THE TENNESSEE AND OHIO VALLEYS AND MUCH OF THE CENTRAL APPALACHIANS, NOV 27-28.
THE PETS (BASED ON THE 0Z MODEL UPDATE CYCLE) SHOW AT LEAST A 30% CHANCE OF
3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND ONE INCH (1.5
INCHES ACROSS TENNESSEE) IN THE MODERATE RISK AREA, FURTHER SUPPORTED BY THE
UNCALIBRATED ECENS. A BROADER AREA OF SLIGHT RISK (20 TO 40% CHANCE) OF HEAVY
PRECIPITATION IS EXPANDED SPATIALLY COMPARED TO YESTERDAY TO INCLUDE PARTS OF
THE NORTHEAST, MID-ATLANTIC, OHIO, TENNESSEE, AND MIDDLE AND LOWER MISSISSIPPI
VALLEYS, AND APPALACHIANS, NOV 27-29.
SURFACE LOW PRESSURE ALONG THE GULF OF MEXICO IN ADDITION TO THE PREDICTED
ACTIVE PATTERN ACROSS THE EAST SUPPORTS A SLIGHT RISK (20-40%) OF EPISODIC HIGH
WINDS WHICH IS SIGNIFICANTLY EXPANDED IN TODAY’S OUTLOOK COMPARED TO YESTERDAY,
ENCOMPASSING MUCH OF THE EASTERN THIRD OF THE CONUS, LOWER MISSISSIPPI VALLEY,
AND COASTAL TEXAS, NOV 27-29. A MODERATE RISK OF PERIODS OF HIGH WINDS IS
DESIGNATED FOR THE OHIO AND TENNESSEE VALLEYS, APPALACHIANS, MID-ATLANTIC, AND
SOUTHEAST FOR THE SAME PERIOD GIVEN INCREASED CHANCES INDICATED IN THE ECENS
WIND PETS AND INCREASED CONFIDENCE IN THE MODELS REGARDING THE POTENTIAL ACTIVE
PATTERN.
MID-LEVEL TROUGHING PREDICTED THROUGHOUT WEEK-2 ACROSS THE EASTERN CONUS IS
CONDUCIVE TO THE PASSAGE OF MULTIPLE FRONTS ACROSS THE REGION AND SURFACE LOWS
TRACKING ACROSS THE EASTERN CANADIAN-U.S. BORDER. THIS PATTERN SUPPORTS A
SLIGHT RISK (20-40% CHANCE) OF PERIODS OF HEAVY LAKE EFFECT SNOW ACROSS PARTS
OF THE GREAT LAKES AND NORTHEAST THROUGHOUT WEEK-2.
SURFACE HIGH PRESSURE PREDICTED OVER MUCH OF MAINLAND ALASKA, THE YUKON, AND
BRITISH COLUMBIA COMBINED WITH ADJACENT LOW PRESSURE OVER THE GULF OF ALASKA
MAY SUPPORT INCREASED CHANCES FOR HIGH GAP WINDS ACROSS SOUTHEASTERN ALASKA.
THE PETS INDICATE AT LEAST A 20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE AND 40 MPH IN COASTAL AREAS. AT THIS TIME THERE ARE INSUFFICIENT
SIGNALS IN THE DETERMINISTIC MODELS TO SUPPORT THE DESIGNATION OF AN ASSOCIATED
HIGH WIND HAZARD AT THE TIME.
FORECASTER: MELISSA OU
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