856  
FXUS21 KWNC 122028  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST JANUARY 12 2018  
 
SYNOPSIS: AT THE START OF THE HAZARDS PERIOD, SURFACE HIGH PRESSURE OVER THE  
EAST COAST STATES IS FORECAST TO MOVE OFFSHORE, FOLLOWED BY THE LEADING EDGE OF  
ANOTHER ARCTIC AIR MASS. THIS AIR MASS SHOULD BE IN PLACE ACROSS THE EASTERN  
HALF OF THE CONUS BY JAN 17, AND LAST FOR SEVERAL DAYS. MEANWHILE, A SERIES OF  
NORTH PACIFIC STORM SYSTEMS ARE PREDICTED TO AFFECT THE WEST COAST STATES, THE  
NORTHERN AND CENTRAL INTERMOUNTAIN REGION, AND THE NORTHERN ROCKIES DURING THE  
3-7 DAY PERIOD. ACROSS THE ALASKA DOMAIN, STORM ACTIVITY IS EXPECTED ACROSS THE  
WESTERN AND SOUTHERN COASTS OF ALASKA, BUT NONE OF THIS ACTIVITY WARRANTS  
HAZARDOUS DESIGNATIONS AT THIS TIME. DURING THE WEEK-2 PERIOD, THE OVERALL  
CIRCULATION PATTERN IS FORECAST TO BE LOW AMPLITUDE, WITH MID-LEVEL LOW  
PRESSURE OVER THE WESTERN HALF OF THE CONUS, AND MID-LEVEL HIGH PRESSURE OVER  
THE EASTERN HALF OF THE CONUS.  
 
HAZARDS  
 
PERIODS OF MUCH BELOW NORMAL TEMPERATURES FOR MOST OF THE CENTRAL AND EASTERN  
CONUS, MON-THU, JAN 15-18.  
 
MUCH ABOVE NORMAL TEMPERATURES FOR PARTS OF SOUTHERN MAINLAND ALASKA, MON-TUE,  
JAN 15-16.  
 
PERIODS OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND NORTHERN  
CALIFORNIA, MON-THU, JAN 15-18.  
 
HIGH WINDS FOR THE PACIFIC NORTHWEST COASTAL REGION, WED-THU, JAN 17-18.  
 
HIGH SIGNIFICANT WAVE HEIGHTS ALONG THE PACIFIC NORTHWEST COAST, WED-THU, JAN  
17-18.  
 
HEAVY PRECIPITATION FOR THE NORTHERN ROCKIES, TUE-WED, JAN 16-17.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR EASTERN MONTANA, WED-THU, JAN  
24-25.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FROM MOST OF CALIFORNIA EASTWARD ACROSS  
APPROXIMATELY THE SOUTHERN HALVES OF BOTH THE INTERMOUNTAIN REGION AND ROCKIES,  
PORTIONS OF THE PLAINS, AND FROM THE MISSISSIPPI VALLEY TO THE APPALACHIANS,  
SAT-WED, JAN 20-24.  
 
MODERATE RISK OF HEAVY PRECIPITATION FROM THE LOWER MISSISSIPPI VALLEY TO THE  
LOWER OHIO VALLEY, MON-TUE, JAN 22-23.  
 
SEVERE DROUGHT FOR PARTS OF THE GREAT PLAINS, THE SOUTHWEST, THE CENTRAL AND  
SOUTHERN MISSISSIPPI VALLEY, THE SOUTHEAST, AND HAWAII.  
 
DETAILED SUMMARY  
 
FOR MONDAY JANUARY 15 - FRIDAY JANUARY 19: A RIDGE OF SURFACE HIGH PRESSURE IS  
ANTICIPATED OVER THE EAST COAST STATES EARLY IN THIS PERIOD. AS THIS HIGH  
PRESSURE AREA MOVES OFFSHORE, AN ARCTIC FRONT IS EXPECTED TO APPROACH THE  
APPALACHIANS. BY THE MIDDLE OF THE 3-7 DAY PERIOD, ARCTIC AIR IS PREDICTED TO  
BE IN PLACE ACROSS THE EASTERN HALF OF THE CONUS, AT LEAST FOR SEVERAL DAYS.  
MAXIMUM AND MINIMUM TEMPERATURES ACROSS THIS REGION ARE FORECAST TO RANGE FROM  
ABOUT 12-28 DEGREES F BELOW NORMAL. DURING TUE-WED, JAN 16-17, LIGHT SNOW  
ACCUMULATIONS (1-2 INCHES) ARE POSSIBLE ACROSS PORTIONS OF THE MID-ATLANTIC AND  
NORTHEAST, IN ASSOCIATION WITH A PREDICTED FRONTAL PASSAGE. AS OF TODAY,  
FRIDAY, JAN 12, THE 12Z ECMWF AND A FEW 12Z GFS ENSEMBLE MEMBERS INDICATE THE  
DEVELOPMENT OF A COASTAL LOW WITH THE POTENTIAL FOR HEAVIER SNOWFALL.  
 
A SERIES OF NORTH PACIFIC CYCLONIC SYSTEMS ARE ANTICIPATED TO MOVE INTO THE  
WEST COAST STATES DURING THIS TIME. PERIODS OF HEAVY PRECIPITATION (RAIN AND  
HIGH ELEVATION SNOW) ARE EXPECTED FOR THE PACIFIC NORTHWEST AND NORTHERN  
CALIFORNIA BETWEEN JAN 15-18 (4-8 INCHES, LIQUID EQUIVALENT). ON JAN 16-17, AN  
AREA OF HEAVY PRECIPITATION (RAIN, SLEET, FREEZING RAIN, AND SNOW ABOVE 5000  
FEET, 1.5 INCHES LIQUID EQUIVALENT) IS INDICATED FOR THE NORTHERN ROCKIES. ON  
JAN 17-18, THE NOAA WAVEWATCH MODEL (WHICH USES THE GFS) PREDICTS THE  
POSSIBILITY OF HAZARDOUS WIND SPEEDS (45-50 KNOTS) AND SIGNIFICANT WAVE HEIGHTS  
(30 FEET OR GREATER) NEAR AND ALONG THE PACIFIC NORTHWEST COAST.  
 
THE STORM SYSTEM RESPONSIBLE FOR A NUMBER OF HAZARDS ON YESTERDAY'S ALASKA MAP  
IS FORECAST TO TIME OFF, WITH ANY RELATED IMPACTS EXPECTED TO END BEFORE THE  
START OF TODAY'S HAZARDS PERIOD. ONLY THE PREDICTED AREA OF MUCH ABOVE NORMAL  
TEMPERATURES (AT LEAST 20-25 DEGREES F ABOVE NORMAL NEAR THE SOUTH COAST) IS  
EXPECTED TO REMAIN.  
 
FOR SATURDAY JANUARY 20 - FRIDAY JANUARY 26: DURING WEEK-2, THE PREDICTED  
CIRCULATION PATTERN FAVORS BELOW NORMAL 500-HPA HEIGHTS OVER THE WESTERN CONUS  
AND THE ALASKA PANHANDLE, WITH MOST REMAINING AREAS HAVING ABOVE NORMAL 500-HPA  
HEIGHTS. THERE IS A SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES IN EASTERN  
MONTANA TOWARD THE END OF THE WEEK-2 PERIOD, THOUGH IT APPEARS THIS ANOMALOUSLY  
COLD AIR MAY NOT SPREAD MUCH BEYOND THIS AREA.  
 
WITH TROUGH ENERGY MOVING ONSHORE OVER THE WESTERN CONUS, AND AIR OF PACIFIC  
ORIGIN DOMINATING MOST OF THE COUNTRY, THERE IS A SLIGHT RISK OF HEAVY  
PRECIPITATION FOR MUCH OF THE CONUS (JAN 20-24). A MODERATE RISK FOR HEAVY  
PRECIPITATION EXISTS FROM THE LOWER MISSISSIPPI VALLEY TO THE LOWER OHIO  
VALLEY, JAN 22-23.  
 
THE U.S. DROUGHT MONITOR, VALID ON JANUARY 9, 2018 INDICATES AN INCREASE IN THE  
COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 7.46% LAST WEEK TO 8.70%  
THIS WEEK. SOME OF THE MORE SIGNIFICANT ADJUSTMENTS MADE THIS WEEK INCLUDE  
IMPROVEMENT (FROM D3 TO D2) IN EASTERN MONTANA, SOME DETERIORATION IN OKLAHOMA  
(D2 TO D3), AND THE INTRODUCTION OF ABNORMAL DRYNESS (D0) IN PARTS OF OREGON.  
 
FORECASTER: ANTHONY ARTUSA  
 

 
 
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