493  
FXUS21 KWNC 292016  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST JANUARY 29 2018  
 
SYNOPSIS: TWO STRONG COLD FRONTS ARE FORECAST TO AFFECT THE CENTRAL AND EASTERN  
U.S. DURING THE FIRST PART OF THE PERIOD, WITH COLD SURFACE HIGH PRESSURE  
DOMINATING IN THE WAKE OF EACH. A STRONG CYCLONIC CIRCULATION ALOFT OVER  
EASTERN NORTH AMERICA AND SURFACE HIGH PRESSURE NOSING SOUTHWARD OUT OF CANADA  
ARE EXPECTED TO BRING PERIOD BOUTS OF ARCTIC AIR TO THE EASTERN HALF OF THE  
U.S. THROUGH THE WEEK-2 PERIOD. UPPER-LEVEL HIGH PRESSURE IS EXPECTED LEAD TO A  
QUIET PERIOD ACROSS CALIFORNIA EARLY IN THE PERIOD, WITH RELATIVELY DRY  
CONDITIONS EXTENDING NORTHWARD ALONG THE WEST COAST DURING WEEK-2. STRONG  
SURFACE HIGH PRESSURE IS FORECAST TO BRING ANOMALOUSLY COLD TEMPERATURES TO  
MUCH OF EASTERN ALASKA EARLY IN THE PERIOD AS STRONG SURFACE LOW PRESSURE  
SYSTEMS REMAIN GENERALLY SOUTH OF THE ALEUTIANS.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THU-SUN, FEB 1-FEB 4.  
 
HEAVY SNOW AT HIGHER ELEVATIONS FOR PARTS OF THE GREAT BASIN, THE NORTHERN AND  
CENTRAL ROCKIES, AND THE PACIFIC NORTHWEST, THU-SUN, FEB 1-FEB 4.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHEAST, THE GREAT  
LAKES, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, THU-MON, FEB  
1-FEB 5.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE ALASKA PANHANDLE AND  
MAINLAND ALASKA, THU-SAT, FEB 1-FEB 3.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND  
EASTERN CONTIGUOUS U.S., TUE-MON, FEB 6-FEB 12.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR THE NORTHEASTERN QUARTER OF  
THE CONTIGUOUS U.S., TUE-MON, FEB 6-FEB 12.  
 
SEVERE DROUGHT ACROSS PARTS OF THE PLAINS, THE CENTRAL AND SOUTHERN ROCKIES,  
THE LOWER AND MIDDLE MISSISSIPPI VALLEY, THE CENTRAL GREAT BASIN, THE TENNESSEE  
VALLEY, THE MID-ATLANTIC, THE SOUTHEAST, AND THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR THURSDAY FEBRUARY 01 - MONDAY FEBRUARY 05: HEAVY RAIN OVER COASTAL PORTIONS  
OF THE PACIFIC NORTHWEST WITH HEAVY SNOW OVER THE CASCADES IS LIKELY DURING THE  
FIRST SEVERAL DAYS OF THE PERIOD. TOTAL PRECIPITATION AMOUNTS ARE EXPECTED TO  
BE IN THE 3-4 INCH RANGE. PERIODS OF HEAVY SNOW ARE ALSO EXPECTED OVER HIGHER  
ELEVATIONS OF THE NORTH GREAT BASIN AND NORTHERN ROCKIES DURING THE SAME  
PERIOD. SNOWFALL AMOUNTS OF 1-3 FEET ARE LIKELY FOR FAVORED LOCALES WITHIN THE  
DEPICTED HAZARD REGION.  
 
MUCH BELOW NORMAL TEMPERATURES ARE LIKELY FOR PARTS OF THE NORTHERN CONUS FROM  
THE HIGH PLAINS EASTWARD DURING THE PERIOD. THERE ARE LIKELY TO BE TWO DISTINCT  
SURGES OF ARCTIC AIR IN THE WAKE OF TWO COLD FRONTS DURING THIS TIME. MINIMUM  
TEMPERATURES OVER THIS REGION ARE LIKELY TO BE 12 DEGREES F BELOW NORMAL OR  
COLDER AT TIMES.  
 
FORECAST NEGATIVE TEMPERATURE ANOMALIES OVER ALASKA ARE LIKELY TO BE WELCOME BY  
MANY, BUT TEMPERATURES DEPARTURES ON THE ORDER OF 20-30 DEGREES F BELOW NORMAL  
ARE HIGHLIGHTED FOR PARTS OF THE SOUTHEAST ALASKA WHERE ITS MOST LIKELY TO BE  
HAZARDOUS. ADDITIONALLY, WITH SURFACE HIGH PRESSURE ANCHORED OVER THE EASTERN  
PART OF THE STATE, CONDITIONS APPEAR FAVORABLE FOR STRONG GAP WINDS OVER THE  
SOUTHERN AND SOUTHERN PARTS OF THE STATE.  
 
TWO MODEST WINTER WEATHER EVENTS ARE LIKELY DURING THIS PERIOD OVER THE CENTRAL  
AND EASTERN CONUS, BUT ARE NOT DEPICTED SINCE THEY ARE NOT FORECAST TO REACH  
HAZARDOUS CRITERIA AT THIS TIME. THE FIRST IS A WEAK WAVE OF LOW PRESSURE AND  
UPPER-LEVEL FORCING THAT IS LIKELY TO PRODUCE A SWATH OF AT LEAST LIGHT SNOW IN  
THE WAKE OF A SURFACE COLD FRONT ON FRIDAY OVER THE NORTHEAST. THE SECOND IS AN  
AREA OF LIGHT TO MODERATE SNOW FROM THE MIDWEST TO THE NORTHEAST ON SUNDAY  
ASSOCIATED WITH THE NEXT FRONTAL PASSAGE.  
 
FOR TUESDAY FEBRUARY 06 - MONDAY FEBRUARY 12: THE WEEK-2 HAZARDS MAP IS  
DOMINATED BY COLD TEMPERATURE HAZARDS WITH MULTIPLE INTRUSIONS OF ARCTIC AIR  
LIKELY DURING THE PERIOD, INTERSPERSED WITH BRIEF PERIODS OF PRE-FRONTAL  
MODERATION. THE DEPICTED HAZARDS COVER THE ENTIRE PERIOD, AND ENCOMPASS THE  
AREA THAT IS MOST LIKELY TO SEE TWO OR MORE DAYS REACH HAZARDOUS CRITERIA. IN  
THIS SENSE THE SPATIAL COVERAGE IS LARGER THAN WOULD BE INFERRED BY THE GEFS  
PROBABILISTIC OUTLOOK ALONE, BUT THAT TOOL IS LIKELY SUFFERING FROM TIMING  
ISSUES AMONG THE VARIOUS MEMBERS. OVERALL THE MAP IS LARGELY CONSISTENT WITH  
THE OFFICIAL WEEK-2 OUTLOOK.  
 
THE WEEK-2 PERIOD LOOKS RELATIVELY DRY OVERALL, WITH LITTLE LOW PRESSURE  
SYSTEMS GENERALLY FORECAST TO TRACK FAIRLY FAR NORTH AND DEPRIVED OF MOISTURE.  
DRY CONDITIONS ARE FORECAST TO CONTINUE INTO THE WEEK-2 PERIOD OVER CALIFORNIA,  
AND BELOW-MEDIAN PRECIPITATION IS EXPECTED FOR MUCH OF THE WEST AND  
SOUTH-CENTRAL CONUS DURING THE PERIOD.  
 
THE U.S. DROUGHT MONITOR, VALID ON JANUARY 23, 2018 INDICATES AN INCREASE IN  
THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 10.03% LAST WEEK TO  
13.60% THIS WEEK. SEVERE DROUGHT CONTINUED TO EXPAND ACROSS THE SOUTHERN GREAT  
PLAINS AND SOUTHWEST THIS PAST WEEK.  
 
FORECASTER: STEPHEN BAXTER  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page