Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXUS21 KWNC 252043
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 25 2014

SYNOPSIS: HIGH PRESSURE ALONG THE ATLANTIC COAST AT THE START OF THE OUTLOOK
PERIOD IS PREDICTED TO MOVE OUT OVER THE ATLANTIC, GRADUALLY GIVING WAY TO A
COLD FRONT APPROACHING FROM THE MISSISSIPPI VALLEY. MOISTURE STREAMING UP FROM
THE SOUTHEAST IS FORECAST TO RESULT IN WET CONDITIONS ACROSS THE MID-ATLANTIC
REGION DURING LATE SUNDAY AND EARLY MONDAY. MUCH COLDER ARCTIC AIR IS EXPECTED
TO MOVE SOUTHWARD ACROSS THE WESTERN AND CENTRAL LOWER 48 STATES FROM THE
BEGINNING OF THE 3-7 DAY PERIOD INTO THE MIDDLE OF WEEK-2. STRONG, SOUTHERLY,
ONSHORE FLOW FROM THE GULF OF ALASKA IS ANTICIPATED TO BRING UNSETTLED WEATHER
TO PARTS OF THE ALASKA RANGE SUNDAY AND MONDAY, AND WARMER TEMPERATURES TO MUCH
OF ALASKA FOR A PROLONGED PERIOD.

HAZARDS

HEAVY RAIN FOR PARTS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND
SOUTHEAST, SUN-MON, DEC 28-29.

HEAVY SNOW FOR MOST OF THE ROCKIES, SUN-TUE, DEC 28-30.

MUCH BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE GREAT PLAINS AND ROCKIES,
MON-WED, DEC 29-JAN 1.

HIGH WINDS FOR THE WEST COAST OF ALASKA, AND SOUTH-CENTRAL ALASKA, SAT-SUN, DEC
27-28.

HEAVY PRECIPITATION FOR PARTS OF THE SOUTH COAST OF ALASKA, INCLUDING KODIAK
ISLAND, SUN-MON, DEC 28-29.

HIGH WINDS FOR THE NORTHERN SIDE OF THE ALASKA RANGE, SUN-MON, DEC 28-29.

MUCH ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE SOUTHERN HALF OF MAINLAND
ALASKA, MON-THU, DEC 29-JAN 1.

SLIGHT RISK FOR MUCH BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE GREAT BASIN,
ROCKIES, AND GREAT PLAINS, FRI-SUN, JAN 2-4.

MODERATE RISK FOR MUCH BELOW NORMAL TEMPERATURES FOR PARTS THE CENTRAL ROCKIES
AND GREAT PLAINS,  FRI-SUN, JAN 2-4.

SLIGHT RISK FOR MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF MAINLAND ALASKA,
FRI-SAT, JAN 2-3.

FLOODING ONGOING OR LIKELY FOR PARTS OF SOUTHERN GEORGIA, NORTHERN FLORIDA, AND
WESTERN OREGON, SUN-MON, DEC 28-29.

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

DETAILED SUMMARY

FOR SUNDAY DECEMBER 28 - THURSDAY JANUARY 01: THIS FORECAST PERIOD IS EXPECTED
TO BEGIN WITH AN UPPER-LEVEL RIDGE AMPLIFYING IN EASTERN ALASKA.  THIS
AMPLIFICATION IS FORECAST TO SEND A STRONG SHORTWAVE DOWN TO THE SOUTHWESTERN
STATES, PRODUCING AN AMPLIFIED, POSITIVELY TILTED LONG-WAVE TROUGH.  AT THE
SURFACE, HIGH PRESSURE IS EXPECTED TO MOVE DOWN FROM WESTERN CANADA TO THE
SOUTHERN PLAINS.  AS IT DOES, STRONG UPSLOPE FLOW IS PREDICTED TO LEAD TO HEAVY
MOUNTAIN SNOW DOWN THE SPINE OF THE ROCKIES FROM THE 28TH TO THE 30TH.
SNOWFALL TOTALS OF 6-12 INCHES IN THE FAVORED UPSLOPE LOCATIONS IS POSSIBLE.
IN ADDITION TO THE SNOW, THIS HIGH PRESSURE IS EXPECTED TO BRING MUCH BELOW
NORMAL TEMPERATURES FROM THE PACIFIC NORTHWEST TO TEXAS, WITH DAILY MINIMUM
TEMPERATURE ANOMALIES FORECAST TO BE 12 TO 20 DEGREES BELOW NORMAL FROM THE
29TH THROUGH JANUARY 1.



AS THIS HIGH SLIDES SOUTHWARD, SURFACE LOW PRESSURE ASSOCIATED WITH ANOTHER
UPPER-LEVEL SHORTWAVES SITUATED OVER TEXAS IS EXPECTED TO MOVE NORTHEASTWARDS.
THE LOW`S ASSOCIATED COLD FRONT IS ANTICIPATED TO BE THE FOCUS FOR HEAVY RAIN
AND POSSIBLE SEVERE WEATHER IN THE SOUTHEAST FROM THE 28TH THROUGH THE 29TH.
MANY LOCATIONS WITH THE GREATEST CHANCE FOR HAZARDOUS WEATHER ARE ALSO THOSE
THAT RECEIVED IT DURING CHRISTMAS EVE.



THE UPPER-LEVEL RIDGE IN ALASKA IS EXPECTED TO LEAD TO A PROLONGED PERIOD OF
STRONG SOUTHERLY FLOW INTO THE STATE.  THIS WILL SET THE STAGE FOR HEAVY
PRECIPITATION ALONG THE SOUTHERN COAST FROM THE 28TH TO THE 29TH, HIGH WINDS
ALONG THE SOUTHERN AND WESTERN COASTS FROM THE 27TH TO THE 28TH AND ALONG THE
ALASKA RANGE FROM THE 28TH TO THE 29TH.  IN ADDITION, THE SOUTHERLY WINDS WILL
LEAD TO MOST OF THE STATE SEEING MUCH ABOVE NORMAL TEMPERATURES.  HOWEVER, THE
HAZARD DENOTED ON THE MAP IS ONLY FOR THOSE LOCATIONS EXPECTED TO SEE DAYTIME
TEMPERATURES NEAR OR ABOVE FREEZING.  THIS SITUATION COULD LEAD TO WARM, MOIST
AIR MOVING ACROSS COLD, WET ROADS, WHICH MAY LEAD TO FROSTY, SLICK DRIVING
CONDITIONS. ADDITIONALLY, ANY LIQUID PRECIPITATION AWAY FROM THE COAST MAY LEAD
TO A FREEZING RAIN HAZARD.

FOR FRIDAY JANUARY 02 - THURSDAY JANUARY 08: THE BEGINNING OF THIS PERIOD IS
EXPECTED TO SEE A SIMILAR PATTERN TO THE END OF THE DAY 3-7 PERIOD, WITH WARM
AIR FUNNELING INTO ALASKA AND COLD AIR STREAMING DOWN INTO THE ROCKIES AND
PLAINS.  THERE IS A SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES STRETCHING
FROM EASTERN WASHINGTON TO TEXAS FOR THE 2ND THROUGH THE 4TH, WITH A MODERATE
RISK IN THE CENTRAL ROCKIES AND GREAT PLAINS, ALSO FROM THE 2ND THROUGH THE
4TH.  IN ADDITION, A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES EXISTS IN
PARTS OF ALASKA FROM THE 2ND THROUGH THE 3RD.  ONCE AGAIN, THIS RISK IS
ASSOCIATED WITH THE POTENTIAL FOR HAZARDOUS DRIVING CONDITIONS CAUSED BY WARM
AIR FLOWING OVER THE COLD GROUND.



THE MOST RECENT U.S. DROUGHT MONITOR, RELEASED ON DECEMBER 24, INDICATES A VERY
SLIGHT DECREASE IN THE AREAL COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2 TO
D4) FROM 17.27 TO 17.18 PERCENT ACROSS THE CONTINENTAL U.S.

FORECASTER: KENNETH PELMAN

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.