926  
FXUS21 KWNC 172135  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST JANUARY 17 2018  
 
SYNOPSIS: A REGION OF MID-LEVEL LOW PRESSURE IS FORECAST TO BE OFF OF VANCOUVER  
ISLAND AT THE START OF THE FORECAST PERIOD, WITH MID-LEVEL HIGH PRESSURE  
FORECAST INITIALLY ACROSS THE EAST. OVER THE COURSE OF THE WEEK THE  
AFOREMENTIONED LOW IS FORECAST TO TRACK INTO THE ROCKIES, WITH ANOTHER  
MID-LEVEL LOW APPROACHING NORTH AMERICA IN ITS WAKE. THE FORMER MID-LEVEL  
DISTURBANCE IS FORECAST TO HELP DEVELOP A SURFACE CYCLONE OVER THE CENTRAL  
PLAINS THAT IS ANTICIPATED TO TRACK TOWARDS THE GREAT LAKES. TRANSITIONING INTO  
WEEK-2, A TENDENCY TOWARDS MID-LEVEL LOW PRESSURE OVER ALASKA (EXCLUDING THE  
ALEUTIANS), THE GREAT BASIN, SOUTHWEST AND GREAT PLAINS IS FORECAST, WITH  
MID-LEVEL HIGH PRESSURE ANTICIPATED OVER THE EAST.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE GREAT BASIN, THE NORTHERN ROCKIES,  
CALIFORNIA, AND THE PACIFIC NORTHWEST, SAT-MON, JAN 20-JAN 22.  
 
HIGH WINDS ACROSS COASTAL PORTIONS OF THE PACIFIC NORTHWEST, SUN, JAN 21.  
 
HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF CALIFORNIA AND THE  
PACIFIC NORTHWEST, SAT-SUN, JAN 20-JAN 21.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE  
CENTRAL GREAT BASIN, THE SOUTHERN ROCKIES, THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, SAT-SUN, JAN 20-JAN 21.  
 
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE CENTRAL PLAINS, THE  
CENTRAL GREAT BASIN, AND THE NORTHERN PLAINS, SAT, JAN 20.  
 
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE MISSISSIPPI  
VALLEY, THE GREAT LAKES, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS,  
SUN, JAN 21.  
 
HEAVY SNOW ACROSS PORTIONS OF THE GREAT LAKES AND THE UPPER MISSISSIPPI VALLEY,  
SUN-TUE, JAN 21-JAN 23.  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHEAST AND THE GREAT LAKES,  
MON-TUE, JAN 22-JAN 23.  
 
HIGH WINDS ACROSS COASTAL PORTIONS OF THE MID-ATLANTIC AND THE NORTHEAST,  
MON-WED, JAN 22-JAN 24.  
 
HIGH WINDS ACROSS PORTIONS OF SOUTHERN INTERIOR ALASKA, THE SOUTH COAST OF  
ALASKA, AND KODIAK ISLAND, SUN-WED, JAN 21-JAN 24.  
 
HIGH WINDS ACROSS PARTS OF THE BROOKS RANGE AND ST. LAWRENCE, SAT-TUE, JAN  
20-JAN 23.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF MAINLAND ALASKA, SUN-WED, JAN  
21-JAN 24.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHWESTERN  
QUARTER OF THE CONUS, THU-SAT, JAN 25-JAN 27.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF NEW MEXICO AND  
WESTERN TEXAS, SUN-MON, JAN 28-JAN 29.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHEAST, THE SOUTHERN  
APPALACHIANS, THE LOWER MISSISSIPPI VALLEY, THE SOUTHERN PLAINS, AND THE  
TENNESSEE VALLEY, THU-MON, JAN 25-JAN 29.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF MAINLAND ALASKA  
AND THE ALEUTIANS, THU-SUN, JAN 25-JAN 28.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF MAINLAND  
ALASKA, THU-SAT, JAN 25-JAN 27.  
 
HIGH WINDS ACROSS PORTIONS OF THE SOUTH COAST OF ALASKA, THU-SAT, JAN 25-JAN 27.  
 
SEVERE DROUGHT FOR PARTS OF THE GREAT PLAINS, THE SOUTHWEST, THE CENTRAL AND  
SOUTHERN MISSISSIPPI VALLEY, THE SOUTHEAST, AND HAWAII.  
 
DETAILED SUMMARY  
 
FOR SATURDAY JANUARY 20 - WEDNESDAY JANUARY 24: A PAIR OF CLOSED 500-HPA LOWS  
ARE FORECAST TO APPROACH THE PACIFIC NORTHWEST DURING THE COURSE OF WEEK-1. THE  
FIRST IS ANTICIPATED TO OPEN UP OVER THE GREAT BASIN AS A POSITIVELY-TILTED  
TROUGH, AND SHIFT INTO THE GREAT PLAINS DURING THE NEXT FEW DAYS. AS THIS  
FEATURE APPROACHES THE ROCKIES, SURFACE CYCLOGENESIS IS FORECAST OVER THE  
CENTRAL PLAINS. THIS SURFACE LOW IS FORECAST TO DEEPEN AS THE MID-LEVEL TROUGH  
TAKES ON A SLIGHTLY NEGATIVE TILT, AND TRACK TOWARDS THE GREAT LAKES. THE  
SECOND MID-LEVEL LOW IS FORECAST TO APPROACH THE WEST COAST LATER IN WEEK-1,  
BRINGING ANOTHER SHOT OF PACIFIC MOISTURE INTO THE WEST.  
 
PERIODIC HEAVY PRECIPITATION (DAILY TOTALS EXCEEDING 2 INCHES OF LIQUID  
EQUIVALENT, WITH SNOW AT HIGHER ELEVATIONS AND RAIN ELSEWHERE) IS FORECAST IN  
ASSOCIATION WITH EACH OF THE MID-LEVEL FEATURES FROM THE PREVIOUS PARAGRAPH FOR  
NORTHERN CALIFORNIA, THE SIERRA-NEVADAS, WESTERN OREGON, AND WESTERN AND  
NORTHERN WASHINGTON INTO NORTHERN IDAHO ON JANUARY 20-22. SNOW LEVELS ARE  
LIKELY TO BEGIN HIGH, AND DROP WITH TIME AS THE COLD-CORE SYSTEMS MOVE OVER THE  
REGION. RAINFALL AMOUNTS IN EXCESS OF 6 INCHES ARE POSSIBLE WITH THIS SYSTEM  
ALONG THE COAST THAT COULD HELP TRIGGER MUDSLIDES IN AREAS SUSCEPTIBLE FROM  
FIRES OVER THE PAST SEVERAL MONTHS. SNOW TOTALS IN THE SIERRA-NEVADAS AND  
CASCADES WITH THIS EVENT COULD EXCEED 3 FEET IN MANY PLACES. THE INITIAL SURGE  
OF MOISTURE ON THE 20TH APPEARS LIKELY TO BE FURTHER NORTH (OVER OREGON AND  
WASHINGTON) THAN THE SECOND PERIOD OF PACIFIC MOISTURE COMING ASHORE ON THE  
21ST AND 22ND (OVER NORTHERN CALIFORNIA AND OREGON). HIGH WINDS (40 KNOTS OR  
GREATER) ARE POSSIBLE ACROSS COASTAL PARTS OF THE PACIFIC NORTHWEST ON JAN 21,  
AS WELL AS HIGH SIGNIFICANT WAVE HEIGHTS (18 FEET OR GREATER) ALONG COASTAL  
PARTS OF THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, JAN 20-21.  
 
IN ASSOCIATION WITH THE FIRST TROUGH MOVING INLAND, A PERIOD OF HIGH WINDS  
(SUSTAINED AT 30 KNOTS OR GREATER) IS LIKELY ACROSS THE CENTRAL PLAINS, THE  
CENTRAL ROCKIES, THE CENTRAL GREAT BASIN, THE SOUTHERN ROCKIES, THE SOUTHERN  
PLAINS, AND THE SOUTHWEST JAN 20 TO 21. MARGINALLY ELEVATED FIRE WEATHER  
CONDITIONS, THOUGH NOT DEPICTED ON THE MAP, ARE ALSO FORECAST ACROSS PORTIONS  
OF EASTERN NEW MEXICO AND WEST TEXAS ON JAN 20 AND WEST-CENTRAL TEXAS ON JAN 21  
DUE TO THE POTENTIAL FOR DRY AND BREEZY CONDITIONS.  
 
WITH THE FIRST TROUGH MOVING INLAND, A SURGE OF PACIFIC MOISTURE INTO THE  
ROCKIES APPEARS LIKELY ON THE 20TH. THIS MAY LEAD TO HEAVY SNOW (EXCEEDING 8  
INCHES IN 24 HOURS) ON THE 20TH ACROSS PORTIONS OF CENTRAL ROCKIES, THE CENTRAL  
PLAINS, THE CENTRAL GREAT BASIN, AND THE NORTHERN PLAINS. AROUND THIS SAME  
TIME, SURFACE CYCLOGENESIS IS LIKELY TO BE OCCURRING OVER THE CENTRAL PLAINS.  
THIS SYSTEM IS FORECAST TO LIFT TOWARDS THE GREAT LAKES ON THE 21ST. A ROUND OF  
HEAVY SNOW (TOTALS UP TO A FOOT) REMAINS POSSIBLE FROM EASTERN NEBRASKA THROUGH  
THE GREAT LAKES ON THE 21ST AS THE TROWAL BECOMES DEFINED WITH THE DEEPENING  
LOW PRESSURE. AS THIS LOW MOVES NORTHEASTWARD TOWARD NEW ENGLAND BY JAN 23,  
PARTS OF THE GREAT LAKES MAY RECEIVE HEAVY SNOW JAN 21 TO 23, AND PARTS OF NEW  
ENGLAND MAY RECEIVE HEAVY SNOW WITH LOCALIZED AREAS OF ICING AND FREEZING RAIN.  
THESE AREAS MAY RECEIVE UP TO A FOOT OF SNOW OR GREATER IN 24-HOURS. THE  
POTENTIAL FOR ICING IMPACTS FOR NEW ENGLAND ARE STILL EXPECTED TO BE LIMITED AT  
THIS TIME. GULF MOISTURE AVAILABILITY FOR THIS SYSTEM APPEARS SOMEWHAT LIMITED  
BY THE ANTECEDENT COLD AIR OUTBREAK OVER THE EAST KEEPING CONDITIONS DRY OVER  
THE EASTERN U.S., THUS NO HEAVY RAIN OR SEVERE WEATHER THREATS ARE ANTICIPATED  
AT THIS TIME WITH THE COLD FRONT OF THIS SYSTEM.  
 
SURFACE CYCLONES ARE FORECAST IN THE BERING SEA AND NORTHEAST PACIFIC DURING  
THE COURSE OF WEEK-1, BUT THEIR OVERALL IMPACTS ON ALASKA ARE LIKELY TO BE  
MUTED. INSTEAD, A SHIFT TO NORTHEASTERLY FLOW OUT OF THE ARCTIC CIRCLE AND  
YUKON APPEARS TO BE A MORE LIKELY THREAT AS COLD AIR SETTLES ACROSS THE STATE.  
MODELS SUGGEST THE POTENTIAL FOR A HIGH WIND EVENT ALONG AND DOWNWIND OF THE  
BROOKS RANGE ON JAN 20 TO 23, IN ASSOCIATION WITH NORTHEASTERLY FLOW THAT COULD  
INDUCE KATABATIC EFFECTS. SIMILAR GAP WINDS ARE POSSIBLE FURTHER SOUTH ALONG  
THE ALEUTIAN AND ALASKAN RANGES BEGINNING ON THE 21ST AND LASTING THROUGH THE  
24TH, WITH WINDS POTENTIALLY GUSTING TO NEAR 100 MPH FOR YAKUTAT. THESE HIGH  
WINDS ARE LIKELY TO BE FUELED BY MUCH BELOW-NORMAL TEMPERATURES (MINIMUM  
TEMPERATURE ANOMALIES OF -25 DEGREES F OR GREATER) BUILDING ACROSS THE STATE AS  
COLD AIR FILTERS SOUTHWESTWARD DURING THE 21ST THROUGH 23RD. LASTLY, HIGH WINDS  
COULD ALSO IMPACT ST. LAWRENCE ISLAND ON JAN 20 TO 23, AS THE BERING SEA HAS  
NOT FROZEN IN THE VICINITY OF THE ISLAND YET THIS SEASON, AND FREEZING SPRAY  
FROM THE STRONG NORTHEAST WINDS COULD DEVASTATE COASTAL COMMUNITIES ALONG THE  
WINDWARD SHORE.  
 
FOR THURSDAY JANUARY 25 - WEDNESDAY JANUARY 31: MID-LEVEL TROUGHING IS  
ANTICIPATED TO DEVELOP ACROSS MAINLAND ALASKA AND THE ALASKA PANHANDLE AS WELL  
AS THE WESTERN HALF OF THE CONUS FROM THE BEGINNING TO MIDDLE OF WEEK-2. A  
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES IS FORECAST ACROSS MAINLAND  
ALASKA AND THE ALEUTIANS JAN 25 TO 28 AND THE NORTHWESTERN QUARTER OF THE CONUS  
JAN 25 TO 27. IN THESE HIGHLIGHTED REGIONS, THE GEFS PROBABILISTIC EXTREMES  
TOOL GIVES AT LEAST A 20% CHANCE OF THE DAILY MINIMUM TEMPERATURES BEING BELOW  
THE 15TH CLIMATOLOGICAL PERCENTILE. ECMWF REFORECAST GUIDANCE DURING WEEK-2  
ALSO SKEWS COLD FOR EACH OF THE AFOREMENTIONED REGIONS, FURTHER SUPPORTING THE  
POTENTIAL COLD RISKS. A MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES IS  
FORECAST FOR PORTIONS OF WESTERN AND INTERIOR MAINLAND ALASKA DURING JAN 25 TO  
27 DUE TO MODEL ENSEMBLE MEAN FORECASTS INDICATING MINIMUM TEMPERATURE  
ANOMALIES GENERALLY BEING 25 TO 30 DEGREES F BELOW NORMAL.  
 
A SLIGHT RISK OF MUCH ABOVE-NORMAL PRECIPITATION IS FORECAST FOR PARTS OF THE  
GULF STATES JAN 25 TO 29. THIS AREA IS ISOLATED BY THE ECMWF PROBABILISTIC  
EXTREMES TOOL WHERE AT LEAST A 20% CHANCE OF AN INCH OF RAIN OVER 3-DAYS IS  
POSSIBLE, AND GENERALLY WHERE THERE IS A 20% CHANCE OF THE 3-DAY TOTAL REACHING  
THE 85TH PERCENTILE OR GREATER. THE GEFS PROBABILISTIC EXTREMES TOOL EXHIBITS  
FAR WEAKER SIGNALS THAT ARE SHIFTED WELL TO THE NORTH, AND APPEAR TIED TO A WET  
BIAS IN THE MODEL, AND THUS IT IS DISCOUNTED HERE.  
 
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: MELISSA OU  
 

 
 
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