028  
FXUS21 KWNC 162023  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST JANUARY 16 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 AND THE WEST  
IS FORECAST, WITH MID-LEVEL HIGH PRESSURE ANTICIPATED OVER THE EAST.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE GREAT BASIN, THE NORTHERN ROCKIES,  
CALIFORNIA, THE PACIFIC NORTHWEST, AND THE SOUTHWEST, FRI-MON, JAN 19-JAN 22.  
 
HIGH WINDS ACROSS COASTAL PORTIONS OF THE PACIFIC NORTHWEST, SAT, JAN 20.  
 
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE CENTRAL PLAINS, AND THE  
CENTRAL GREAT BASIN, SAT, JAN 20.  
 
HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND  
MIDDLE MISSISSIPPI VALLEY, AND THE GREAT LAKES, SUN, JAN 21.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, THE CENTRAL AND  
SOUTHERN ROCKIES, AND THE SOUTHWEST, SAT, JAN 20.  
 
MUCH BELOW-NORMAL TEMPERATURES ACROSS PORTIONS OF THE SOUTHEAST AND THE LOWER  
MISSISSIPPI VALLEY, FRI, JAN 19.  
 
MUCH BELOW-NORMAL TEMPERATURES ACROSS MUCH OF WESTERN AND INTERIOR MAINLAND  
ALASKA, SUN-TUE, JAN 21-23.  
 
HIGH WINDS ACROSS PORTIONS OF THE BROOKS RANGE AND AREAS IMMEDIATELY TO ITS  
SOUTHWEST, FRI-TUE, JAN 19-JAN 23.  
 
HIGH WINDS ACROSS PORTIONS OF THE ALEUTIAN AND ALASKA RANGES AND AREAS  
IMMEDIATELY TO THEIR SOUTH, SAT-TUE, JAN 20-23.  
 
HIGH WINDS AND POTENTIAL FREEZING SPRAY FOR ST. LAWRENCE ISLAND, FRI-TUE, JAN  
19-23.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF CALIFORNIA,  
OREGON, AND NEVADA, WED-THU, JAN 24-JAN 25.  
 
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR WESTERN AND INTERIOR  
MAINLAND ALASKA, WED-FRI, JAN 24-26.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR ALASKA WITH THE EXCEPTION OF  
THE WESTERN ALEUTIANS, WED-TUE, JAN 24-JAN 30.  
 
SLIGHT RISK OF HEAVY PRECIPITATION EXTENDING FROM SOUTHEAST TEXAS THROUGH  
GEORGIA, WED-FRI, JAN 24-JAN 26.  
 
SEVERE DROUGHT FOR PARTS OF THE GREAT PLAINS, THE SOUTHWEST, THE CENTRAL AND  
SOUTHERN MISSISSIPPI VALLEY, THE SOUTHEAST, AND HAWAII.  
 
DETAILED SUMMARY  
 
FOR FRIDAY JANUARY 19 - TUESDAY JANUARY 23: 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 EXTREME NORTHERN IDAHO ON JANUARY 19-22. 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 19TH AND 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). IN ASSOCIATION WITH  
THE FIRST TROUGH MOVING INLAND, A PERIOD OF HIGH WINDS (SUSTAINED AT 35 MPH OR  
GREATER) IS LIKELY ACROSS THE FOUR CORNERS REGION INTO THE SOUTHERN AND CENTRAL  
PLAINS ON THE 20TH. MARGINALLY ELEVATED FIRE WEATHER CONDITIONS, THOUGH NOT  
DEPICTED ON THE MAP, ARE ALSO FORECAST ACROSS PORTIONS OF EASTERN NEW MEXICO  
AND WEST TEXAS ON THE 19TH AND 20TH 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 COLORADO, WYOMING, AND  
NEBRASKA. 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. THE GFS HAS TRENDED FURTHER NORTH TOWARDS THE ECMWF SINCE  
YESTERDAY, LIMITING ANY POTENTIAL ICING IMPACTS FOR NEW ENGLAND AS OPPOSED TO  
YESTERDAY'S OUTLOOK. 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. 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. THIS COLD AIR OUTBREAK IS LIKELY TO RESULT IN A  
BRIEF PERIOD OF MUCH BELOW-NORMAL TEMPERATURES (MINIMUM TEMPERATURE ANOMALIES  
OF -12 DEGREES F OR GREATER) FOR A SMALL REGION NEAR THE GULF OF MEXICO ON THE  
19TH BEFORE CONDITIONS BEGIN TO MODERATE.  
 
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 THE 19TH THROUGH 23RD 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 20TH AND 21ST  
RESPECTIVELY AND LASTING THROUGH THE 23RD, 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. THE GEFS AND CANADIAN MODEL GUIDANCE IS MOST BULLISH ON THE  
COLD, WHILE THE 0Z ECMWF ENSEMBLE DEPICTS A MARGINAL EVENT. LASTLY, HIGH WINDS  
COULD ALSO IMPACT ST. LAWRENCE ISLAND ON THE 19TH THROUGH 23RD, 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 WEDNESDAY JANUARY 24 - TUESDAY JANUARY 30: DURING WEEK-2, ANOMALOUS 500-HPA  
TROUGHING IS FORECAST TO EXTEND FROM ALASKA THROUGH THE GREAT BASIN, WITH  
ANOMALOUS RIDGING SITUATED EAST OF THE MISSISSIPPI VALLEY. IN THIS SCENARIO,  
COLD HAZARDS ARE POSSIBLE FOR THE WEST, WITH AN INCREASED RISK OF HEAVY  
PRECIPITATION FOR THE EAST DUE TO ENHANCED FLOW OUT OF THE GULF OF MEXICO.  
 
A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES IS FORECAST ACROSS PORTIONS OF  
OREGON, NORTHERN CALIFORNIA, AND NEVADA FOR THE 24TH AND 25TH. HERE THE GEFS  
PROBABILISTIC EXTREMES TOOL GIVES AT LEAST A 20% CHANCE OF THE DAILY MINIMUM  
TEMPERATURES BEING BELOW THE 15TH CLIMATOLOGICAL PERCENTILE. A SLIGHT RISK OF  
MUCH BELOW-NORMAL TEMPERATURES ALSO EXISTS FOR ALL OF MAINLAND ALASKA  
THROUGHOUT WEEK-2 IN ASSOCIATION WITH LIKELY NORTHEASTERLY FLOW OFF THE ARCTIC  
OCEAN OR OUT OF THE YUKON. HERE THE GEFS PROBABILISTIC EXTREMES TOOL ALSO GIVES  
AT LEAST A 20% CHANCE OF BEING IN THE BOTTOM 15TH PERCENTILE OF CLIMATOLOGICAL  
MINIMUM TEMPERATURES THROUGHOUT THE WEEK. 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 THE 24TH THROUGH 26TH DUE TO ENSEMBLE MEAN FORECASTS OF MINIMUM  
TEMPERATURE ANOMALIES FROM THE 12Z GEFS AND 12Z DETERMINISTIC EUROPEAN  
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 ON THE 24TH THROUGH 26TH. THIS AREA IS ISOLATED BY THE ECMWF  
PROBABILISTIC EXTREMES TOOL WHERE AT LEAST A 40% CHANCE OF AN INCH AND A HALF  
OF RAIN THROUGHOUT THE AFOREMENTIONED PERIODS IS POSSIBLE, WHILE ODDS OF  
PRECIPITATION BEING ABOVE THE 85TH CLIMATOLOGICAL PERCENTILE ON THOSE DAYS  
EXCEEDS 30%. 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: CPC FORECASTER  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page