Prognostic Meteorological Discussion
Issued by NWS

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FXUS21 KWNC 211929
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 21 2014

SYNOPSIS: A STRONG STORM SYSTEM IS PREDICTED TO REACH THE GREAT LAKES BY
MONDAY. SURFACE HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS MUCH OF THE REST
OF THE LOWER 48 STATES DURING THE FIRST HALF OF THE PERIOD. A COLD FRONT IS
FORECAST TO SINK SOUTHWARD FROM CANADA BY WEDNESDAY, BRINGING COLD, ARCTIC AIR
TO NORTHERN PORTIONS OF THE EASTERN AND CENTRAL CONTIGUOUS U.S. ANOTHER COLD,
SURFACE HIGH IS PREDICTED TO SPREAD SOUTHWARD FROM CANADA DURING THE BEGINNING
AND MIDDLE OF WEEK-2. A SERIES OF SURFACE LOWS ARE ANTICIPATED TO DEVELOP OVER
THE BERING SEA, ALEUTIANS, AND GULF OF ALASKA DURING DAYS 3-7.

HAZARDS

LOCALIZED HEAVY LAKE EFFECT SNOW FOR PARTS OF MICHIGAN AND WISCONSIN, MON-WED,
NOV 24-26.

LOCALIZED HEAVY LAKE EFFECT SNOW FOR PARTS OF THE LOWER GREAT LAKES, TUE-WED,
NOV 25-26.

POSSIBLE LOCALIZED FLOODING FOR PARTS OF THE GREAT LAKES, MON, NOV 24.

HIGH WINDS FOR PARTS OF THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES, MON-TUE,
NOV 24-25.

MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN PLAINS, UPPER
MISSISSIPPI VALLEY, AND UPPER GREAT LAKES, WED-FRI, NOV 26-28.

HEAVY SNOW FOR PARTS OF THE CASCADE MOUNTAINS, MON-TUE, NOV 24-25.

HEAVY SNOW FOR PARTS OF THE NORTHERN AND CENTRAL ROCKIES AND NORTHERN AND
CENTRAL GREAT BASIN, MON-WED, NOV 24-26.

MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE CENTRAL ROCKIES, MON-TUE, NOV
24-25.

SLIGHT CHANCE FOR MUCH BELOW NORMAL DAILY MINIMUM TEMPERATURES ACROSS MUCH OF
THE CENTRAL AND EASTERN NORTHERN TIER OF THE CONUS, SAT-MON, NOV 29-DEC 1.

SEVERE DROUGHT FOR THE CENTRAL AND SOUTHERN GREAT PLAINS, SOUTHWEST, SOUTHEAST,
TENNESSEE VALLEY, PACIFIC NORTHWEST, GREAT BASIN, AND CALIFORNIA.

DETAILED SUMMARY

FOR MONDAY NOVEMBER 24 - FRIDAY NOVEMBER 28: A STRONG STORM SYSTEM IS PREDICTED
TO REACH THE GREAT LAKES AT THE BEGINNING OF THE PERIOD, BRINGING LOCALIZED
HEAVY LAKE EFFECT SNOW TO PARTS OF MICHIGAN AND WISCONSIN, MONDAY TO TUESDAY
AND THE LOWER GREAT LAKES ON TUESDAY. THIS STORM MAY ALSO BRING HIGH WINDS TO
PARTS OF THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES MONDAY TO TUESDAY, WITH
SUSTAINED WIND SPEEDS POSSIBLY REACHING 30-40 KNOTS OR GREATER. AS THIS STORM
EXITS THE U.S. INTO CANADA, A SURFACE LOW IS EXPECTED TO DEVELOP OVER THE UPPER
GREAT LAKES ALONG A COLD FRONT DRAPED ACROSS THE NORTHERN TIER ON WEDNESDAY,
LEADING TO ENHANCED CHANCES FOR ANOTHER BOUT OF LAKE EFFECT SNOW ACROSS PARTS
OF THESE GREAT LAKES AREAS ON WEDNESDAY. THE GREATEST LIKELIHOOD FOR
SIGNIFICANT SNOWFALL IS OVER MICHIGAN AND WISCONSIN, WITH THE POTENTIAL FOR
HALF AN INCH OF LIQUID EQUIVALENT OR GREATER IN A 24-HOUR PERIOD. CURRENTLY,
LOWER SNOW ACCUMULATIONS ARE EXPECTED FOR AREAS EAST OF LAKES ERIE AND ONTARIO.
THIS COLD FRONT IS ANTICIPATED TO MOVE SOUTHWARD ACROSS THE CENTRAL AND EASTERN
CONUS, BRINGING MUCH BELOW NORMAL TEMPERATURES TO PARTS OF THE NORTHERN PLAINS,
UPPER MISSISSIPPI VALLEY, AND UPPER GREAT LAKES, WEDNESDAY TO FRIDAY. THESE
AREAS MAY EXPERIENCE DAILY TEMPERATURES 16 DEGREES OR GREATER BELOW NORMAL,
WITH MINIMUM TEMPERATURES REACHING THE NEGATIVE SINGLE DIGITS IN SOME LOCATIONS.



A MODERATION OF TEMPERATURES IS ANTICIPATED FOR PARTS OF THE GREAT LAKES ON
MONDAY. ABOVE FREEZING TEMPERATURES, IN ADDITION TO EXPECTED RAIN SHOWERS, MAY
LEAD TO LOCALIZED FLOODING OF CREEKS AND LAKES FROM MELTING OF ANTECEDENT LAKE
EFFECT SNOW IN THE GREAT LAKES REGION ON MONDAY. THE GREATEST CHANCES FOR
SIGNIFICANT FLOODING ARE EAST OF LAKES ERIE AND ONTARIO. URBAN SECTIONS OF
BUFFALO MAY EXPERIENCE PONDING AND FLOODING DUE TO THE LARGE VOLUME OF MELT
WATER OVERLOADING DRAINAGE SYSTEMS. THE AREA SOUTH OF LAKE MICHIGAN IS EXPECTED
TO HAVE MINOR FLOODING. THE AFOREMENTIONED COLD FRONT SINKING SOUTHWARD FROM
CANADA IS ANTICIPATED TO PROVIDE FLOOD RELIEF IN THESE AREAS BY TUESDAY DUE TO
THE EXPECTATION THAT TEMPERATURES WILL GO BELOW FREEZING.



A SERIES OF SURFACE LOWS ARE EXPECTED TO DEVELOP OVER THE NORTHEAST PACIFIC
OCEAN. STRONG ONSHORE FLOW ASSOCIATED WITH THIS PATTERN IS ANTICIPATED TO BRING
LOCALIZED HEAVY SNOW TO PARTS OF THE CASCADE MOUNTAINS MONDAY TO TUESDAY. THIS
AREA MAY RECEIVE AN INCH OR GREATER OF LIQUID EQUIVALENT IN A 24-HOUR PERIOD.
IN GENERAL, SNOW ELEVATION LEVELS ARE EXPECTED TO RISE TO BETWEEN 7000 TO 8000
FEET BY TUESDAY, WITH THE EXCEPTION OF SNOW LEVELS POTENTIALLY REMAINING AT
3000 FEET NEAR THE CANADIAN BORDER.



SURFACE HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE WESTERN HALF OF THE CONUS
DURING THIS PERIOD, LEADING TO STRONG, UPSLOPE FLOW ACROSS THE ROCKIES FOR MUCH
OF THIS PERIOD. THIS PATTERN IS EXPECTED TO BRING EPISODES OF LOCALIZED HEAVY
SNOW TO HIGHER ELEVATION AREAS OF THE NORTHERN AND CENTRAL ROCKIES AND NORTHERN
AND CENTRAL GREAT BASIN MONDAY TO WEDNESDAY. SOME AREAS MAY RECEIVE AN INCH OF
LIQUID EQUIVALENT OR GREATER IN A 24-HOUR PERIOD. THIS NORTHWESTERLY, UPSLOPE
FLOW IS ALSO EXPECTED TO BRING MUCH BELOW NORMAL TEMPERATURES TO PARTS OF THE
CENTRAL ROCKIES ON MONDAY AND TUESDAY. DAILY MINIMUM TEMPERATURES MAY REACH THE
NEGATIVE SINGLE DIGITS IN SOME AREAS.

FOR SATURDAY NOVEMBER 29 - FRIDAY DECEMBER 05: THERE IS MUCH MORE CONSENSUS
AMONGST MODELS TODAY COMPARED TO YESTERDAY, REGARDING THE POTENTIAL FOR ANOTHER
SURGE OF COLD, ARCTIC AIR FROM CANADA INTO NORTHERN PARTS OF THE CONUS FROM THE
BEGINNING TO MIDDLE OF WEEK-2. AN AREA FOR SLIGHT RISK OF MUCH BELOW NORMAL
TEMPERATURES IS HIGHLIGHTED ACROSS MUCH OF THE CENTRAL AND EASTERN NORTHERN
TIER OF THE CONUS NEXT SATURDAY TO THE FOLLOWING MONDAY. THESE AREAS MAY
EXPERIENCE DAILY MINIMUM TEMPERATURES BELOW THE 10TH PERCENTILE COMPARED TO
CLIMATOLOGY.



IN GENERAL, A RELATIVELY ZONAL PATTERN IS PREDICTED FOR WEEK-2, FAVORING
ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE WESTERN TWO-THIRDS OF THE CONUS, AND
NORMAL TEMPERATURES FOR THE EASTERN THIRD OF THE CONUS, EXCLUDING THE AREA OF
BELOW NORMAL TEMPERATURES ACROSS THE GREAT LAKES MENTIONED ABOVE. NORMAL TO
ABOVE NORMAL 500-HPA HEIGHTS ARE FORECAST FOR ALASKA, BRINGING NORMAL TO ABOVE
NORMAL TEMPERATURES TO THE STATE.



THE MOST RECENT U.S. DROUGHT MONITOR, RELEASED ON NOVEMBER 20, INDICATES A
SLIGHT DECREASE IN THE AREAL COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2 TO
D4) FROM 17.27 PERCENT TO 17.13 PERCENT ACROSS THE CONTINENTAL U.S.

FORECASTER: MELISSA OU

$$



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