026
FXUS21 KWNC 171932
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 17 2023
SYNOPSIS: AS WEEK-2 STARTS, A FETCH OF COLD AIR SHOULD BE CROSSING THE GREAT
LAKES BETWEEN SURFACE LOW PRESSURE NORTH OF THE EASTERN CONTIGUOUS U.S. (CONUS)
AND A COLD HIGH PRESSURE COVERING THE EASTERN TWO-THIRDS OF THE CONUS. THIS
BRINGS AN INCREASED RISK OF HEAVY LAKE-EFFECT SNOW DOWNWIND IN PARTS OF WESTERN
PENNSYLVANIA AND UPSTATE NEW YORK. THE COLD AIR WILL ENCAPSULATE THE CENTRAL
AND EASTERN CONUS MOST OF THE WEEK, BUT THE RISK OF HAZARDOUSLY COLD
TEMPERATURES IS LIMITED TO THE CENTRAL AND WESTERN GULF COAST REGION, WHERE
SOME LOCATIONS COULD SEE THEIR FIRST FROST OR FREEZE OF THE SEASON. ONE OR TWO
WEAK MID-LEVEL DISTURBANCES COULD TRAVERSE THE CENTRAL AND EASTERN CONUS,
POTENTIALLY BRINGING MODERATE RAIN TO THE LOWER MISSISSIPPI VALLEY AND THE
SOUTHEAST, WITH SNOW POSSIBLE FARTHER NORTH. BUT ANY PRECIPITATION ASSOCIATED
WITH THESE FEATURES IS EXPECTED TO REMAIN BELOW HAZARDS THRESHOLDS.
HAZARDS
SLIGHT RISK FOR HEAVY SNOW DOWNWIND FROM LAKES ERIE AND ONTARIO, SAT, NOV 25.
SLIGHT RISK FOR MUCH BELOW NORMAL TEMPERATURES ALONG AND NEAR THE GULF OF
MEXICO COAST FROM THE FLORIDA PANHANDLE THROUGH SOUTHERN TEXAS, SUN-TUE, NOV
26-28.
DETAILED SUMMARY
FOR MONDAY NOVEMBER 20 - FRIDAY NOVEMBER 24:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY NOVEMBER 25 - FRIDAY DECEMBER 01: ALL GUIDANCE SHOWS SURFACE LOW
PRESSURE NORTH OF THE CONUS MOVING AWAY FROM THE NATION WHILE COLD HIGH
PRESSURE HAS MOVED FROM NORTHERN CANADA SOUTHEASTWARD, SETTLING INTO THE
CENTRAL AND EASTERN CONUS. ON DAY 8 (SAT NOV 25), THE PRESSURE GRADIENT BETWEEN
THESE TWO SYSTEMS CREATES A FETCH OF COLD AIR THAT CROSSES LAKES ERIE AND
ONTARIO, WHICH ARE SLIGHTLY WARMER THAN NORMAL. THIS IS A FAVORABLE PATTERN FOR
HEAVY LAKE-EFFECT SNOWFALL DOWNWIND FROM LAKES ERIE AND ONTARIO. TODAY’S
GUIDANCE GENERALLY DEPICTS A LESS ROBUST SITUATION THAN INDICATED YESTERDAY,
BUT A SLIGHT RISK FOR HEAVY LAKE-EFFECT SNOW STILL EXISTS, AND IS POSTED THERE
FOR THE SATURDAY AFTER THANKSGIVING.
THE COLD HIGH PRESSURE ORIGINATING IN NORTHERN CANADA IS EXPECTED TO PREVAIL
ACROSS THE CENTRAL AND EASTERN CONUS FOR MOST OF THE PERIOD, AT LEAST THROUGH
THE THANKSGIVING HOLIDAY WEEKEND. THE COLD WEATHER IS EXPECTED TO BE MOST
IMPACTFUL IN SOUTHERN TEXAS AND ALONG THE CENTRAL AND WESTERN GULF COAST
REGION. DURING SUN-TUE NOV 26-28, THE COLD AIR IS EXPECTED TO BE COVERING THE
SOUTHERN TIER OF THE CONUS, AND RADIATIONAL COOLING DURING CALM, CLEAR TO
PARTLY CLOUDY NIGHTS COULD BRING THE FIRST FROST OR FREEZE OF THE SEASON TO A
LARGE PART OF THIS AREA.
A PREPONDERANCE OF THE MODELS SHOW ONE OR TWO WEAK MID-LEVEL IMPULSES MOVING
ACROSS THE EASTERN HALF OF THE CONUS DURING WEEK-2, BUT THERE IS POOR AGREEMENT
ON THE STRENGTH, TIMING, AND LOCATION OF THESE SYSTEMS. THESE FEATURES COULD
TRIGGER ONE OR TWO EPISODES OF MODERATE RAINFALL IN PARTS OF THE SOUTHERN
PLAINS, LOWER MISSISSIPPI VALLEY AND SOUTHEAST, WITH ACCUMULATING SNOW POSSIBLE
FARTHER NORTH FROM THE FRONT RANGE OF THE ROCKIES EASTWARD THROUGH PARTS OF THE
GREAT PLAINS, UPPER MIDWEST, GREAT LAKES, AND NORTHEAST. NO HAZARDS ARE POSTED
AT THIS TIME, HOWEVER, DUE TO THE RELATIVELY WEAK NATURE OF THESE SYSTEMS AND
THE BROAD DISPARITY AMONG THE TOOLS REGARDING THE EVOLUTION OF THESE FEATURES.
STRONG RIDGING OVER ALASKA FAVORS ANOMALOUSLY WARM TEMPERATURES ACROSS THE
STATE. DURING THE EARLY AND MIDDLE PART OF WEEK-2, THE EUROPEAN AND GEFS
ENSEMBLE MEANS SHOW TEMPERATURES AVERAGING 6 TO 12 DEG. F ABOVE NORMAL ACROSS
THE NORTH SLOPE AND OVER INTERIOR SECTIONS OF SOUTH-CENTRAL AND SOUTHWESTERN
MAINLAND ALASKA. THIS COULD RESULT IN POOR ICE CONDITIONS IN PORTIONS OF
INTERIOR SOUTH-CENTRAL AND SOUTHWESTERN ALASKA WHERE TEMPERATURES COULD REACH
ABOVE FREEZING FOR SEVERAL CONSECUTIVE DAYS. IN ADDITION, AN ANOMALOUSLY STRONG
FETCH OF MOIST AIR FROM THE NORTH PACIFIC OCEAN INTO SOUTHERN ALASKA IS
EXPECTED AT TIMES DURING WEEK-2, BRINGING THE RISK OF SOME LIQUID RAIN OR
RAIN-ON-SNOW EVENTS INTO PARTS OF SOUTHERN AND SOUTHWESTERN MAINLAND ALASKA. IT
STILL APPEARS THAT NO POSTED HAZARDS ARE APPROPRIATE AT THIS TIME, BUT THE
SITUATION WILL CONTINUE TO BE CLOSELY MONITORED.
FORECASTER: RICH TINKER
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