274  
FXUS21 KWNC 122121  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 12 2018  
 
SYNOPSIS: A COLD FRONT STRETCHING FROM THE GREAT LAKES TO THE SOUTHEAST IS  
FORECAST TO MIGRATE SOUTHEASTWARD ACROSS THE EASTERN HALF OF THE LOWER 48  
STATES DURING THE 3 TO 7 DAY PERIOD. TOWARD THE END OF WEEK-2, A FRONT  
STRETCHING FROM THE UPPER MISSISSIPPI VALLEY TO CALIFORNIA IS EXPECTED TO  
SLOWLY MOVE SOUTHEASTWARD ACROSS THE CONTIGUOUS U.S. AND REMAIN STATIONARY  
THROUGHOUT WEEK-2. A SERIES OF SURFACE LOWS IS PREDICTED TO FORM OVER THE  
BERING SEA AND GULF OF ALASKA DURING THE 3 TO 7 DAY AND WEEK-2 PERIOD, WHILE  
SURFACE HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS MUCH OF MAINLAND ALASKA  
DURING THE SAME PERIOD.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL APPALACHIANS AND THE OHIO VALLEY,  
THU-FRI, FEB 15-FEB 16.  
 
HEAVY SNOW ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THE NORTHERN ROCKIES, AND  
THE NORTHERN GREAT BASIN, SAT-SUN, FEB 17-FEB 18.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE CENTRAL PLAINS, THE  
NORTHERN PLAINS, AND THE NORTHERN ROCKIES, FRI-SUN, FEB 16-FEB 18.  
 
HIGH WINDS ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE CENTRAL ROCKIES, THE  
SOUTHERN PLAINS, AND THE CENTRAL PLAINS, MON, FEB 19.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHERN PLAINS AND THE  
NORTHERN ROCKIES, THU-FRI, FEB 15-FEB 16 AND MON, FEB 19.  
 
HIGH WINDS ACROSS PORTIONS OF THE ALEUTIANS, MON, FEB 19.  
 
HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF THE ALEUTIANS, MON, FEB  
19.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTH SLOPE OF ALASKA,  
THU-MON, FEB 15-FEB 19.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE WESTERN HALF  
OF THE CONUS, TUE-THU, FEB 20-FEB 22.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE  
NORTHWESTERN QUARTER OF THE CONUS, TUE-THU, FEB 20-FEB 22.  
 
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE PACIFIC  
NORTHWEST, THE NORTHERN ROCKIES, THE NORTHERN GREAT BASIN, AND THE NORTHERN  
PLAINS, TUE-THU, FEB 20-FEB 22.  
 
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR PORTIONS OF MAINLAND ALASKA  
AND THE ALEUTIANS, TUE-SUN, FEB 20-FEB 25.  
 
MODERATE RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN  
HALF OF MAINLAND ALASKA, TUE-FRI, FEB 20-FEB 23.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE LOWER MISSISSIPPI  
VALLEY, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN  
APPALACHIANS, THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO VALLEY, TUE-MON,  
FEB 20-FEB 26.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHEAST, THE MID-ATLANTIC, THE  
NORTHEAST, AND THE CENTRAL APPALACHIANS.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHERN APPALACHIANS,  
THE LOWER MISSISSIPPI VALLEY, THE CENTRAL APPALACHIANS, THE OHIO VALLEY, AND  
THE TENNESSEE VALLEY.  
 
FLOODING LIKELY ACROSS PORTIONS OF THE SOUTHERN APPALACHIANS, THE OHIO VALLEY,  
AND THE TENNESSEE VALLEY.  
 
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE LOWER  
MISSISSIPPI VALLEY, THE CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE TENNESSEE  
VALLEY, THE SOUTHERN ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC,  
CALIFORNIA, THE SOUTHEAST, THE SOUTHERN APPALACHIANS, THE SOUTHERN PLAINS, AND  
THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR THURSDAY FEBRUARY 15 - MONDAY FEBRUARY 19: A COLD FRONT STRETCHING FROM THE  
GREAT LAKES TO THE SOUTHWEST IS PREDICTED TO PROPAGATE SOUTHEASTWARD ACROSS THE  
CONUS FROM THE BEGINNING TO MIDDLE OF THE 3 TO 7 DAY PERIOD. THIS FRONT MAY  
BRING HEAVY RAIN TO PARTS OF THE CENTRAL APPALACHIANS AND THE OHIO VALLEY FEB  
15 TO 16. SOME MODELS INDICATE RAINFALL TOTALS IN SOME AREAS REACHING 2 INCHES  
OR GREATER IN A 24-HOUR PERIOD.  
 
A COLD FRONT IS PREDICTED TO APPROACH THE PACIFIC NORTHWEST FEB 17 AND 18,  
WHILE A STATIONARY FRONT IS ANTICIPATED TO FORM OVER THE ROCKIES THOUGHOUT THE  
3 TO 7 DAY PERIOD. STRONG ONSHORE FLOW COMBINED WITH FORCING ASSOCIATED WITH  
THE STATIONARY FRONT MAY BRING HEAVY SNOW FEB 17 TO 18 ACROSS THE CASCADES AND  
NORTHERN ROCKIES. THE 0Z DETERMINISTIC ECMWF INDICATES HIGHER PRECIPITATION  
AMOUNTS THAN THE 6Z DETERMINISTIC GFS, WITH THE ECMWF SHOWING A POTENTIAL FOR  
LOCALIZED AREAS REACHING AND EXCEEDING 1.5 INCHES OF LIQUID EQUIVALENT IN  
24-HOURS. ADDITIONALLY, THIS PATTERN FAVORS HIGH WINDS IN THE LEE OF THE  
ROCKIES. A HIGH WINDS HAZARD IS HIGHLIGHTED AT FIRST ACROSS PARTS OF THE  
CENTRAL ROCKIES, THE CENTRAL PLAINS, THE NORTHERN PLAINS, AND THE NORTHERN  
ROCKIES FEB 16 TO 18, FOLLOWED BY THE CENTRAL ROCKIES, THE SOUTHERN PLAINS, AND  
THE CENTRAL PLAINS FEB 19. SUSTAINED WIND SPEEDS MAY REACH 30 KNOTS OR GREATER  
IN LOCALIZED HIGHLIGHTED REGIONS.  
 
PERIODS OF SURFACE HIGH PRESSURE IS ANTICIPATED TO BUILD ACROSS THE NORTHERN  
PART OF THE PACIFIC NORTHWEST AND THE NORTHERN AND CENTRAL PLAINS DURING THE 3  
TO 7 DAY PERIOD. THIS PATTERN MAY USHER IN MUCH BELOW NORMAL TEMPERATURES  
ACROSS PARTS OF THE NORTHERN PLAINS AND THE NORTHERN ROCKIES FEB 15 TO 16 AND  
FEB 19. SOME AREAS MAY EXPERIENCE MINIMUM TEMPERATURES WITH NEGATIVE ANOMALIES  
OF 20 DEGREES F OR GREATER WITH TEMPERATURES REACHING NEGATIVE DOUBLE DIGITS  
(DEG F).  
 
TWO STORM SYSTEMS ARE PREDICTED TO FORM OVER THE BERING SEA DURING THE 3 TO 7  
DAY PERIOD. THE FIRST ONE MAY BRING HIGH WINDS AND SIGNIFICANT WAVE HEIGHTS TO  
MAINLY THE CENTRAL PART OF THE ALEUTIANS ON FEB 16. HOWEVER, THE EXPECTED WIND  
SPEEDS AND HIGH WINDS ARE NOT EXPECTED TO REACH HAZARDS CRITERIA AND THEREFORE  
ARE NOT INCLUDED ON THE MAP AT THIS TIME. A SECONDARY STORM IS FORECAST TO  
DEVELOP OVER THE WESTERN PORTION OF THE ALEUTIANS BY FEB 19, WITH A GREATER  
LIKELIHOOD OF BRINGING HIGH WINDS (45 KNOTS OR GREATER) AND SIGNIFICANT WAVES  
(30 FEET OR GREATER) TO THE ALEUTIANS. MEANWHILE, SURFACE HIGH PRESSURE IS  
ANTICIPATED TO BUILD ACROSS MUCH OF MAINLAND ALASKA, INCREASING CHANCES FOR  
MUCH ABOVE NORMAL TEMPERATURES ACROSS PARTS OF THE NORTH SLOPE THROUGHOUT THE 3  
TO 7 DAY PERIOD. SOME AREAS ACROSS THE NORTH SLOPE MAY EXPERIENCE TEMPERATURE  
DEPARTURES 40 DEGREES F OR GREATER THAN NORMAL.  
 
FOR TUESDAY FEBRUARY 20 - MONDAY FEBRUARY 26: A HIGHLY AMPLIFIED PATTERN IS  
EXPECTED FOR WEEK-2, WITH MID-LEVEL RIDGING ACROSS ALASKA AND THE EASTERN HALF  
OF THE CONUS AND TROUGHING ACROSS THE WESTERN HALF OF THE CONUS. A BROAD AREA  
OF SLIGHT RISK IS HIGHLIGHTED ACROSS MUCH OF THE WESTERN HALF OF THE CONUS  
THROUGHOUT WEEK-2, EXCLUDING PARTS OF THE SOUTHWEST, SOUTHERN ROCKIES, AND  
TEXAS FEB 20 TO 22. AN AREA OF MODERATE RISK IS IDENTIFIED FOR A SLIGHTLY  
SMALLER SUBSET REGION OF THE SLIGHT AREA FOR FEB 20 TO 22, WHILE A HIGH RISK  
AREA IS HIGHLIGHTED ACROSS NORTHERN PARTS OF THE PACIFIC NORTHWEST AND THE  
NORTHERN PLAINS FEB 20 TO 22. THE GEFS REFORECAST TOOL INDICATES A 20 PERCENT  
CHANCE OR GREATER OF REACHING THE LOWEST 1ST PERCENTILE COMPARED TO NORMAL FOR  
LOCALIZED PARTS OF THE NORTHWEST AND THE NORTHERN PLAINS, FEB 20 AND 21.  
 
MID-LEVEL RIDGING ACROSS ALASKA IS ANTICIPATED TO CONTINUE THE PATTERN FOR  
ANOMALOUSLY WARMER TEMPERATURES FOR MANY PARTS OF THE REGION. A BROAD AREA OF  
SLIGHT RISK FOR MUCH ABOVE NORMAL TEMPERATURES IS HIGHLIGHTED ACROSS MOST OF  
MAINLAND ALASKA AND THE ALEUTIANS, EXCLUDING SOUTHEASTERN ALASKA, THROUGHOUT  
WEEK-2. A MODERATE RISK AREA EXISTS FOR THE NORTHERN HALF OF MAINLAND ALASKA  
FEB 20 TO 23. THE GEFS REFORECAST TOOL PREDICTS THESE AREAS REACHING THE 85TH  
PERCENTILE OR GREATER.  
 
THE 0Z GEFS AND 6Z ECMWF ENSEMBLE MODELS INDICATE A STATIONARY FRONT STRETCHING  
FROM THE OHIO VALLEY TO THE SOUTHERN PLAINS THROUGHOUT WEEK-2. THIS PATTERN  
SUPPORTS HEAVY RAINFALL ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY, THE  
TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN APPALACHIANS, THE  
SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO VALLEY THROUGHOUT WEEK-2. BOTH THE  
GEFS AND ECMWF REFORECAST TOOL INDICATES 3-DAY RAINFALL AMOUNTS REACHING NEARLY  
THE 85TH PERCENTILE OR GREATER IN THE HIGHLIGHTED REGION. THIS POTENTIAL FOR  
PROLONGED HEAVY RAINFALL IN COMBINATION WITH REGIONS IN THIS AREA CURRENTLY  
BEING AFFECTED BY FLOODING MAY INCREASE CHANCES FOR FLOODING DURING WEEK-2.  
 
THE U.S. DROUGHT MONITOR, VALID ON FEB 6 2018 INDICATES A SLIGHT INCREASE IN  
THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 17.21% LAST WEEK TO  
18.44% THIS WEEK. DRYNESS AND DROUGHT HAVE INCREASED IN SPATIAL COVERAGE AND/OR  
INTENSIFIED OVER PORTIONS OF NORTHERN TEXAS AND WESTERN OKLAHOMA. SOME  
DETERIORATION IN CONDITIONS IS ALSO NOTED OVER THE SOUTHEAST.  
 
FORECASTER: MELISSA OU  
 

 
 
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