865  
FXUS21 KWNC 292115  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST DECEMBER 29 2017  
 
SYNOPSIS: SEVERAL WEAK SURFACE LOW PRESSURE SYSTEMS ARE FORECAST TO RAPIDLY  
MOVE ACROSS THE GREAT LAKES REGION AND NORTHEAST DURING THE 3-7 DAY PERIOD.  
ARCTIC AIR MASSES ARE PREDICTED TO DOMINATE THE COUNTRY EAST OF THE CONTINENTAL  
DIVIDE. SURFACE HIGH PRESSURE IS EXPECTED TO PREVAIL OVER AREAS WEST OF THE  
CONTINENTAL DIVIDE DURING DAYS 3-7. IN THE ALASKA DOMAIN, A VIGOROUS LOW  
PRESSURE SYSTEM IS ANTICIPATED TO MOVE EASTWARD FROM THE ALEUTIANS TO THE  
PANHANDLE DURING THIS SAME PERIOD. DURING WEEK-2, A SURGE OF LOWER-LATITUDE  
EASTERN PACIFIC MOISTURE IS FORECAST TO MOVE INTO THE AMERICAN SOUTHWEST, WHILE  
A RELATIVELY COLD PATTERN PERSISTS OVER MUCH OF THE EASTERN LOWER 48 STATES.  
 
HAZARDS  
 
MUCH BELOW-NORMAL TEMPERATURES FOR MOST AREAS EAST OF THE CONTINENTAL DIVIDE,  
MON-WED, JAN 1-3.  
 
MUCH BELOW-NORMAL TEMPERATURES FOR MOST OF THE EASTERN HALF OF THE CONUS,  
THU-FRI, JAN 4-5.  
 
MUCH ABOVE-NORMAL TEMPERATURES FOR MOST OF MAINLAND ALASKA SOUTH OF THE BROOKS  
RANGE, TUE-WED, JAN 2-3.  
 
HEAVY PRECIPITATION NEAR THE SOUTH-CENTRAL ALASKA COAST, MON-TUE, JAN 1-2.  
 
HEAVY SNOW DOWNWIND OF THE GREAT LAKES, MON-TUE, JAN 1-2.  
 
HIGH WINDS IN SOUTHERN ALASKA, MON-TUE, JAN 1-2.  
 
SIGNIFICANT WAVES ALONG PART OF THE SOUTH-CENTRAL ALASKA COAST, MON-TUE, JAN  
1-2.  
 
FLOODING LIKELY IN PARTS OF THE PACIFIC NORTHWEST.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR APPROXIMATELY THE EASTERN  
HALF OF THE CONUS, SAT-SUN, JAN 6-7.  
 
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FROM APPROXIMATELY THE  
MISSISSIPPI RIVER EASTWARD TO THE ATLANTIC COAST, SAT-SUN, JAN 6-7.  
 
HIGH RISK OF MUCH BELOW-NORMAL TEMPERATURES IN THE GENERAL VICINITY OF THE  
LOWER GREAT LAKES REGION, AND IN THE CAROLINAS AND EASTERN GEORGIA, SAT JAN 6.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE NORTHERN GREAT PLAINS,  
TUE-WED, JAN 9-10.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FROM CENTRAL AND SOUTHERN CALIFORNIA  
EASTWARD TO THE CENTRAL AND SOUTHERN ROCKIES, SAT-MON, JAN 6-8.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR SOUTHERN CALIFORNIA, SOUTHERN NEVADA,  
AND ARIZONA INCLUDING THE VICINITY OF THE FOUR CORNERS REGION, SAT-MON, JAN 6-8.  
 
SEVERE DROUGHT ACROSS THE GREAT PLAINS, THE SOUTHWEST, THE MIDDLE AND LOWER  
MISSISSIPPI VALLEY, AND HAWAII.  
 
DETAILED SUMMARY  
 
FOR MONDAY JANUARY 01 - FRIDAY JANUARY 05: ARCTIC AIR MASSES ARE FORECAST TO  
DOMINATE THE CENTRAL AND EASTERN CONUS DURING THE 3-7 DAY PERIOD. TEMPERATURES  
ARE GENERALLY EXPECTED TO RANGE FROM 12-30 DEGREES BELOW NORMAL, WITH SOME OF  
THE COLDEST ANOMALOUS TEMPERATURES IN EASTERN MONTANA EARLY IN THIS PERIOD (36  
DEGREES BELOW NORMAL).  
 
AREAS OF MODERATE TO HEAVY SNOW ARE PREDICTED DOWNSTREAM OF THE GREAT LAKES ON  
JAN 1-2. LAKE SURFACE TEMPERATURES ARE STILL ABOVE FREEZING IN MOST LOCATIONS  
THOUGH LIKELY DROPPING QUICKLY IN THE COMING DAYS. OPEN LAKES AND COLD AIR SET  
THE STAGE FOR LAKE ENHANCED SNOWS, AND MANY LOCATIONS JUST RECEIVED SIGNIFICANT  
SNOWS, SUCH AS ERIE, PA AND THE TUG HILL PLATEAU EAST OF LAKE ONTARIO IN  
UPSTATE NEW YORK.  
 
ON JAN 2, BEHIND THE INITIAL COLD FRONT, SURFACE HIGH PRESSURE CENTERED OVER  
THE MIDDLE MISSISSIPPI VALLEY SUPPORTS FAIRLY STRONG EASTERLY WINDS ACROSS THE  
EAST COAST OF FLORIDA, POTENTIALLY INCREASING THE THREAT OF RIP CURRENTS.  
 
LATE IN THIS PERIOD, A SIGNIFICANT WINTER STORM IS FORECAST TO DEVELOP NEAR THE  
NORTHEAST COAST. HOWEVER, RECENT MODEL TRENDS DISPLACE THE EXPECTED STORM TRACK  
WELL OFFSHORE, AND THE NORTHEAST MAY ONLY GET SOME OF THE GUSTY WINDS  
ASSOCIATED WITH THE REAR-SIDE (WESTERN SIDE) OF THE STORM SYSTEM. WINDS OF  
30-35 MPH ARE ANTICIPATED ON JAN 5.  
 
FLOODING IS LIKELY TO CONTINUE ACROSS PARTS OF THE PACIFIC NORTHWEST, DUE TO  
THE HEAVY PRECIPITATION RECEIVED DURING THE PAST WEEK.  
 
A STORMY PATTERN IS FORECAST FOR SOUTHERN ALASKA DURING THE FIRST FEW DAYS OF  
THE NEW YEAR. HIGH WINDS (45 KNOTS) OVER THE ALASKA PENINSULA ON JAN 1 ARE  
LIKELY TO SPREAD EASTWARD INTO SOUTH-CENTRAL ALASKA AND THE ALASKA RANGE WHERE  
SOUTHERLY FLOW COULD GET ENHANCED BY TERRAIN DURING JAN 1-2. THE SOUTHERLY FLOW  
IS LIKELY TO BRING MUCH ABOVE NORMAL TEMPERATURES TO CENTRAL AND WESTERN  
ALASKA, JAN 2-3. STRONG SOUTHERLY FLOW INTERACTING WITH HIGHER TERRAIN IS ALSO  
EXPECTED TO GENERATE HEAVY PRECIPITATION (2-3 INCHES IN 24 HOURS, FOR MULTIPLE  
DAYS) ACROSS THE EASTERN SLOPES OF KODIAK ISLAND, THE KENAI PENINSULA, AND INTO  
PRINCE WILLIAM SOUND. SUSTAINED SOUTHERLY FLOW, WITH A LONG TRAJECTORY (FETCH)  
OVER THE GULF OF ALASKA IS PREDICTED TO RESULT IN LARGE WAVES (SIGNIFICANT WAVE  
HEIGHTS OF ABOUT 30 FEET) ALONG THE SOUTH-CENTRAL ALASKA COAST, JAN 1-2.  
FINALLY, SNOWY, WINDY CONDITIONS ARE POSSIBLE IN NORTHWESTERN ALASKA ON JAN 1,  
BUT NO HAZARDOUS THRESHOLDS ARE LIKELY TO BE EXCEEDED.  
 
FOR SATURDAY JANUARY 06 - FRIDAY JANUARY 12: A DEEP TROUGH IS FORECAST TO  
DOMINATE MUCH OF THE CENTRAL AND EASTERN CONUS FOR MUCH OF WEEK-2, ALTHOUGH IT  
IS EXPECTED TO WEAKEN TOWARDS THE MIDDLE OF THE PERIOD. THIS LEADS TO A SLIGHT  
RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR APPROXIMATELY THE EASTERN HALF OF  
THE CONUS ON JAN 6-7. A MODERATE RISK AREA EXTENDS FROM ABOUT THE MISSISSIPPI  
RIVER TO THE ATLANTIC COAST DURING THIS SAME PERIOD, WHILE TWO EMBEDDED HIGH  
RISK AREAS OF MUCH BELOW-NORMAL AREAS ARE EXPECTED ON JAN 6. SEVERAL DAYS  
LATER, ANOTHER SHOT OF COLD AIR IS PREDICTED TO CROSS THE CANADIAN BORDER IN  
EASTERN MONTANA AND THE NORTHERN PLAINS, JAN 9-10. A SLIGHT RISK OF HEAVY  
PRECIPITATION IS FORECAST OVER MUCH OF THE SOUTHWEST CONUS, INCLUDING CENTRAL  
AND SOUTHERN CALIFORNIA, JAN 6-8. AN EMBEDDED MODERATE RISK AREA IS ALSO  
FORECAST, WHICH ENCOMPASSES MUCH OF THE SAME REGION AND TIME. THIS WIDESPREAD  
AREA OF EXPECTED PRECIPITATION CAN BE TRACED BACK TO AN UNSEASONABLY DEEP  
TROUGH THAT IS FORECAST TO EXTEND INTO THE LOWER LATITUDES OF THE EASTERN  
PACIFIC (ABOUT 20N, AND 125-135W) PRIOR TO THIS PERIOD.  
 
THE U.S. DROUGHT MONITOR, UPDATED ON DEC 26, SHOWS A DECREASE IN THE COVERAGE  
OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 6.97% LAST WEEK TO 4.95% THIS  
WEEK. A SIDE-BY-SIDE COMPARISON OF THE LATEST TWO MAPS INDICATES SIGNIFICANT  
DROUGHT IMPROVEMENT IN THE ARKLATEX REGION, WHICH INCLUDES MUCH OF ARKANSAS,  
EASTERN OKLAHOMA, NORTHEASTERN TEXAS, AND SMALL PARTS OF NEIGHBORING LOUISIANA.  
DETERIORATION IS NOTED IN THE FLORIDA PANHANDLE AND VIRGINIA, AMONG OTHER AREAS.  
 
FORECASTER: ANTHONY ARTUSA  
 

 
 
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