328  
FXUS21 KWNC 162022  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 16 2018  
 
SYNOPSIS: AN ACTIVE WEATHER PATTERN IS PREDICTED ACROSS THE CONTIGUOUS U.S. AND  
ALASKA DURING THE NEXT TWO WEEKS. DURING THE 3-7 DAY AND WEEK-2 FORECAST  
PERIODS, ON AVERAGE, A FRONTAL ZONE IS EXPECTED TO STRETCH FROM THE SOUTHERN  
GREAT PLAINS NORTHEASTWARD ACROSS THE OHIO VALLEY AND GREAT LAKES REGION. MIXED  
PRECIPITATION TYPES, AND THUNDERSTORMS, ARE ANTICIPATED ACROSS PORTIONS OF THIS  
REGION. IN GENERAL, WARMER THAN NORMAL TEMPERATURES ARE EXPECTED EAST OF THIS  
FRONTAL ZONE, AND COLDER THAN NORMAL TEMPERATURES ARE PREDICTED WEST OF THIS  
FRONTAL ZONE.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE GREAT LAKES AND THE UPPER  
MISSISSIPPI VALLEY, MON, FEB 19.  
 
HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER MISSISSIPPI VALLEY,  
THE CENTRAL APPALACHIANS, THE TENNESSEE VALLEY, THE GREAT LAKES, THE MIDDLE  
MISSISSIPPI VALLEY, THE NORTHEAST, THE SOUTHERN PLAINS, AND THE OHIO VALLEY,  
MON-TUE, FEB 19-FEB 20.  
 
HEAVY RAIN ACROSS 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, WED-THU, FEB 21-FEB 22.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE CENTRAL  
APPALACHIANS, AND THE OHIO VALLEY.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE  
CENTRAL GREAT BASIN, THE SOUTHERN ROCKIES, THE SOUTHERN PLAINS, AND THE  
SOUTHWEST, MON, FEB 19.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL GREAT BASIN, THE  
NORTHERN PLAINS, THE NORTHERN ROCKIES, THE CENTRAL ROCKIES, CALIFORNIA, THE  
NORTHERN GREAT BASIN, THE PACIFIC NORTHWEST, AND THE SOUTHWEST, TUE-WED, FEB  
20-FEB 21.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL PLAINS, THE UPPER  
MISSISSIPPI VALLEY, THE NORTHERN PLAINS, AND THE NORTHERN ROCKIES, MON-FRI, FEB  
19-FEB 23.  
 
HIGH WINDS ACROSS PORTIONS OF MAINLAND ALASKA, MON-WED, FEB 19-FEB 21.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF MAINLAND ALASKA, MON-WED, FEB  
19-FEB 21.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL  
PLAINS, THE CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE NORTHERN ROCKIES, THE  
CENTRAL ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE NORTHERN GREAT  
BASIN, THE UPPER MISSISSIPPI VALLEY, THE ALASKA PANHANDLE, THE PACIFIC  
NORTHWEST, AND THE SOUTHWEST, SAT-FRI, FEB 24-MAR 2.  
 
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR PORTIONS OF MAINLAND ALASKA  
AND THE ALEUTIANS, SAT-MON, FEB 24-FEB 26.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL  
GREAT BASIN, CALIFORNIA, AND THE SOUTHWEST, SAT-SUN, FEB 24-FEB 25.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL  
PLAINS, THE NORTHERN PLAINS, THE NORTHERN ROCKIES, AND THE NORTHERN GREAT  
BASIN, SAT-FRI, FEB 24-MAR 2.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL PLAINS, THE  
LOWER MISSISSIPPI VALLEY, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY,  
THE SOUTHERN APPALACHIANS, THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO  
VALLEY, SAT-MON, FEB 24-FEB 26.  
 
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE LOWER  
MISSISSIPPI VALLEY, THE CENTRAL GREAT BASIN, THE NORTHERN PLAINS, THE SOUTHERN  
ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE SOUTHERN PLAINS, AND  
THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR MONDAY FEBRUARY 19 - FRIDAY FEBRUARY 23: DURING THIS PERIOD, A SURFACE  
ANTICYCLONE INITIALLY OVER ALBERTA IS FORECAST TO MOVE ACROSS THE U.S. NORTHERN  
PLAINS AND UPPER MISSISSIPPI VALLEY, REACHING NEW ENGLAND BY THE END OF THIS  
PERIOD. AS THE LEADING EDGE OF THIS COOLER AIR MASS SHIFTS SOUTHEASTWARD OVER  
THE CENTRAL AND EASTERN CONUS, IT IS ANTICIPATED TO BRING SIGNIFICANT RAINFALL  
(1.5-3.0 INCHES) FROM CENTRAL TEXAS NORTHEASTWARD ACROSS THE OHIO VALLEY AND  
INTO THE EASTERN GREAT LAKES REGION, FEB 19-20. DURING THE ENSUING TWO-DAY  
PERIOD, 1.5-2.5 INCHES OF RAIN IS PREDICTED A LITTLE FARTHER TO THE SOUTHEAST,  
FROM EASTERN TEXAS INTO TENNESSEE AND KENTUCKY. THIS IS GENERALLY IN RESPONSE  
TO THE EXPECTED AMPLIFICATION OF A MID-LEVEL TROUGH WEST OF THAT AREA, AND THE  
DOWNSTREAM RIDGE OVER THE SOUTHEAST. THUNDERSTORMS ARE ALSO A POSSIBILITY,  
ESPECIALLY FROM ABOUT CENTRAL TEXAS TO THE OZARKS REGION. HOWEVER, THE STORM  
PREDICTION CENTER DOES NOT DEPICT A SEVERE THREAT FOR THE REGION DUE TO A  
NUMBER OF REASONS, SOME OF WHICH INCLUDE THE EXPECTATION OF A POSITIVELY TILTED  
500-HPA TROUGH IN THIS VICINITY, AND RESULTING NOMINAL INSTABILITY AND WIND  
SHEAR. FARTHER NORTH, WITH TEMPERATURES NEAR FREEZING ACROSS THE UPPER GREAT  
LAKES REGION, A SWATH OF HEAVY SNOW AND SLEET IS PREDICTED ON FEB 19.  
 
IN LOWER MICHIGAN, WHERE AT LEAST 4-8 INCHES OF SNOW REMAINS ON THE GROUND,  
ALREADY SATURATED SOILS, AND THE INTRODUCTION OF WARMER TEMPERATURES AND RAIN,  
COULD RESULT IN AREAS OF LOCALIZED FLOODING. FOR ADDITIONAL INFORMATION, PLEASE  
CONSULT THE LATEST AVAILABLE STREAM FLOW INFORMATION AT THE NORTH CENTRAL RIVER  
FORECAST CENTER (NCRFC) AT HTTPS://WWW.WEATHER.GOV/NCRFC/ . FLOODING IS ALSO  
POSSIBLE ACROSS PARTS OF MISSISSIPPI AND PENNSYLVANIA.  
 
THE SURFACE HIGH PRESSURE CENTER FROM ALBERTA MENTIONED ABOVE IS EXPECTED TO  
SINK SOUTH AND EAST ACROSS THE NORTHERN AND CENTRAL PLAINS, AND INTO MINNESOTA,  
USHERING IN ARCTIC AIR ON BLUSTERY WINDS. THOUGH PREDICTED WIND SPEEDS ARE NOW  
ANTICIPATED TO DROP BELOW HAZARDOUS THRESHOLDS DURING THIS EVENT, MINIMUM  
TEMPERATURES ARE STILL EXPECTED TO BE DANGEROUSLY COLD, RANGING FROM ABOUT 12  
TO 36 DEGREES BELOW NORMAL. IN THE MOST EXTREME CASE (CENTRAL AND EASTERN PARTS  
OF MONTANA), WHERE THE NORMAL OVERNIGHT LOW IS ABOUT 12 DEGREES F, A DEPARTURE  
OF 36 DEGREES F BELOW NORMAL BRINGS THE FORECASTED TEMPERATURE DOWN TO ABOUT  
-24 DEGREES F. SOME OF THIS UNSEASONABLY COLD AIR IS PREDICTED TO SPILL WEST OF  
THE CONTINENTAL DIVIDE, COVERING MUCH OF THE WESTERN CONUS. HOWEVER, THE  
TEMPERATURE DEPARTURES ARE FORECAST TO RANGE ONLY FROM ABOUT 12 TO 16 DEGREES F  
BELOW NORMAL, MAKING FOR LESS EXTREME CONDITIONS AS COMPARED TO THOSE EAST OF  
THE DIVIDE. FINALLY, HIGH WINDS (ABOUT 30 KNOTS) ARE PREDICTED BY THE 0Z ECMWF  
AND 6Z GFS BOUNDARY LAYER WIND FORECASTS OVER AND EAST OF THE FOUR CORNERS  
REGION ON FEB 19. THIS HAZARD CORRESPONDS WITH THE APPROXIMATE EXPECTED ARRIVAL  
TIME OF THE ARCTIC FRONT FROM CANADA.  
 
IN NORTHERN AND WESTERN ALASKA, TEMPERATURES FROM THE ECMWF AND GFS RUNS ARE  
FORECAST TO RANGE FROM 20-40 DEGREES F ABOVE NORMAL, FEB 19-21. THE LARGEST  
TEMPERATURE DEPARTURES ARE ANTICIPATED OVER THE NORTH SLOPE. THIS MUCH MILDER  
PATTERN IS DUE TO AN EXTENSIVE SOUTHERLY FETCH OF LOW-LEVEL AIR FROM THE NORTH  
PACIFIC, AIDED BY DOWNSLOPE WINDS ACROSS THE NORTHERN SLOPES OF THE BROOKS  
RANGE. SEVERAL BERING SEA CYCLONIC SYSTEMS ARE FORECAST TO BRING HIGH WINDS  
(ABOUT 40 KNOTS) TO THE WEST COAST OF ALASKA, FEB 19-21, INCLUDING ST. LAWRENCE  
ISLAND WELL OFFSHORE. INCIDENTALLY, THOUGH NOT A SPECIFIC HAZARD TO PUT ON THE  
MAP, THERE IS CONSIDERABLY LESS ICE THAN NORMAL IN THE BERING SEA AT THIS TIME.  
THE ICE EDGE IS FAR TO THE NORTH FOR THIS TIME OF YEAR, AND OPEN WATER IS NOW  
BEING ANALYZED WITHIN THE ICE EDGE, EVEN CLOSE TO SHORE AND IN THE  
CHUKCHI/BERING STRAIT REGION. THIS MEANS REPETITIVE SURF COULD BE PROBLEMATIC  
FOR PARTS OF ALASKA'S WEST COAST.  
 
FOR SATURDAY FEBRUARY 24 - FRIDAY MARCH 02: THE WEEK-2 MID-LEVEL FLOW PATTERN  
ACROSS THE FORECAST DOMAIN IS EXPECTED TO FEATURE A RIDGE OVER THE NORTH  
PACIFIC/WESTERN ALASKA, A TROUGH OVER MOST OF WESTERN NORTH AMERICA, AND A  
RIDGE OVER EASTERN NORTH AMERICA. A SLIGHT RISK OF MUCH ABOVE NORMAL  
TEMPERATURES IS INDICATED FOR MUCH OF ALASKA (EXCLUDING THE SOUTHEAST MAINLAND  
AND THE PANHANDLE REGION), DUE TO A PREDICTED MID-TROPOSPHERIC RIDGE, FEB  
24-26. IN CONTRAST, THERE IS A SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES  
ACROSS THE ALASKA PANHANDLE FOR THE WEEK-2 PERIOD. THIS SLIGHT RISK OF MUCH  
BELOW NORMAL TEMPERATURES ALSO INCORPORATES MUCH OF THE WESTERN AND  
NORTH-CENTRAL CONUS, FEB 24-MAR 2, ASSOCIATED WITH A MID-LEVEL TROUGH. A  
MODERATE RISK AREA IS INDICATED OVER THE NORTHERN ROCKIES AND NORTHERN HIGH  
PLAINS FOR THE FULL WEEK-2 PERIOD. ANOTHER MODERATE RISK AREA IS INDICATED OVER  
CALIFORNIA, BUT ONLY FOR FEB 24-25. ACROSS EAST-CENTRAL PORTIONS OF THE LOWER  
48 STATES, THERE IS A SLIGHT RISK OF HEAVY PRECIPITATION FROM CENTRAL TEXAS  
EASTWARD AND NORTHEASTWARD ACROSS THE LOWER AND MIDDLE MISSISSIPPI VALLEY, THE  
OHIO AND TENNESSEE VALLEYS, AND THE SOUTHERN APPALACHIANS, FEB 24-26. THERE ARE  
SUBSTANTIAL DIFFERENCES BETWEEN THE ECMWF ENSEMBLE MEAN AND GEFS PEO  
(PROBABILISTIC OF EXTREMES OUTLOOK) PRECIPITATION TOOLS, THOUGH THE MAIN AXIS  
OF THE EXPECTED HEAVY PRECIPITATION APPEARS CONSISTENT WITH YESTERDAY'S OUTLOOK.  
 
 
 
THE U.S. DROUGHT MONITOR, VALID ON FEB 13, 2018 INDICATES A SLIGHT DECREASE IN  
THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 18.44% LAST WEEK TO  
18.04% THIS WEEK. A FEW OF THE MORE SUBSTANTIAL REVISIONS MADE TO THE MAP THIS  
WEEK INCLUDE AN INCREASE IN D2 COVERAGE ACROSS SOUTHERN CALIFORNIA, THE  
ELIMINATION OF ALL D2 AREAS ACROSS THE GULF COAST STATES FROM LOUISIANA TO  
FLORIDA, AND SIGNIFICANT 1-CATEGORY IMPROVEMENTS RENDERED ACROSS THE CAROLINAS,  
MID-ATLANTIC, AND NORTHEAST.  
 
FORECASTER: ANTHONY ARTUSA  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page