444  
FXUS21 KWNC 222131  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 22 2018  
 
SYNOPSIS: ACTIVE WEATHER IS FORECAST OVER THE U.S. DURING THE FINAL FOUR DAYS  
OF FEBRUARY. AN EXTENSIVE COLD FRONT ASSOCIATED WITH A LOW PRESSURE SYSTEM  
SITUATED OVER THE GREAT LAKES REGION IS EXPECTED TO BRING HEAVY RAIN TO THE  
SOUTHEASTERN U.S. IN THE BEGINNING OF THE 3-7 DAY PERIOD, FOLLOWED BY MORE  
RAINFALL AT THE END OF THE PERIOD CAUSED BY ANOTHER LOW PRESSURE SYSTEM THAT  
EMERGES FROM JUST EAST OF THE ROCKIES. COOL TEMPERATURES ARE EXPECTED TO  
PREVAIL OVER MUCH OF THE WESTERN U.S. DURING THE ENTIRE FORECAST PERIOD, WITH A  
SLIGHT MODERATION DURING WEEK-2 OVER SOUTHERN CALIFORNIA.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF CALIFORNIA, THE PACIFIC NORTHWEST, AND THE  
NORTHERN GREAT BASIN, SUN-TUE, FEB 25-FEB 27.  
 
HEAVY RAIN ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE TENNESSEE  
VALLEY, THE MID-ATLANTIC, THE SOUTHERN APPALACHIANS, THE SOUTHEAST, AND THE  
SOUTHERN PLAINS, SUN-MON, FEB 25-FEB 26.  
 
HEAVY RAIN ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE TENNESSEE  
VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN APPALACHIANS, THE  
SOUTHEAST, AND THE SOUTHERN PLAINS, WED, FEB 28.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE CENTRAL  
APPALACHIANS, THE TENNESSEE VALLEY, THE GREAT LAKES, THE MIDDLE MISSISSIPPI  
VALLEY, THE SOUTHERN PLAINS, AND THE OHIO VALLEY.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE GREAT LAKES, THE MIDDLE  
MISSISSIPPI VALLEY, THE LOWER MISSISSIPPI VALLEY, THE SOUTHERN PLAINS, AND THE  
UPPER MISSISSIPPI VALLEY.  
 
FLOODING LIKELY ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE TENNESSEE  
VALLEY, THE GREAT LAKES, THE MIDDLE MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI  
VALLEY, THE SOUTHERN PLAINS, AND THE OHIO VALLEY.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS MOST OF THE WESTERN HALF OF THE CONUS,  
SUN-THU, FEB 25-MAR 1.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MOST OF THE WESTERN HALF OF  
THE CONUS, FRI-THU, MAR 2-MAR 8.  
 
MODERATE 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, CALIFORNIA, THE NORTHERN GREAT BASIN, THE PACIFIC NORTHWEST,  
AND THE SOUTHWEST, FRI-THU, MAR 2-MAR 8.  
 
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHERN  
PLAINS, THE NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN, FRI-THU, MAR 2-MAR  
8.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA, THE CENTRAL  
GREAT BASIN, THE PACIFIC NORTHWEST, THE NORTHERN GREAT BASIN, AND THE  
SOUTHWEST, FRI-SUN, MAR 2-MAR 4.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE LOWER MISSISSIPPI  
VALLEY, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC,  
THE SOUTHERN APPALACHIANS, THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO  
VALLEY, FRI-TUE, MAR 2-MAR 6.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL PLAINS, THE  
MIDDLE MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN  
PLAINS, SAT-SUN, MAR 3-MAR 4.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF MAINLAND ALASKA, FRI-SAT,  
MAR 2-MAR 3.  
 
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 SUNDAY FEBRUARY 25 - THURSDAY MARCH 01: A SURFACE CYCLONE IS EXPECTED TO BE  
CENTERED OVER WISCONSIN AT THE START OF THE FORECAST PERIOD, BRINGING  
PRECIPITATION TO THE GREAT LAKES REGION AND SPREADING SOUTHEAST THROUGH THE  
MID-ATLANTIC AND TENNESSEE VALLEY. THE CYCLONE IS EXPECTED TO PULL OUT OF THE  
REGION OVER THE WEEKEND, BUT ITS ASSOCIATED COLD FRONT IS EXPECTED TO LAG  
BEHIND AND CONTINUE TO BRING HEAVY RAIN TO THE SOUTHEASTERN U.S. THROUGH  
MONDAY. AFTER THAT FRONT MOVES OUT, A FAST MOVING UPPER-LEVEL TROUGH WILL  
LIKELY BRING MORE RAIN TO THE SAME REGION ON THE LAST DAY OF THE MONTH.  
THEREFORE, A HEAVY RAIN HAZARD IS IDENTIFIED FOR FEB. 28.  
 
A SERIES OF SHORTWAVES IS EXPECTED TO MOVE THROUGH THE PACIFIC NORTHWEST,  
RESULTING IN PERIODS OF MUCH-BELOW NORMAL TEMPERATURES FOR MOST OF THE WESTERN  
AND NORTH-CENTRAL CONUS DURING FEB. 25 - MAR. 1. HEAVY PRECIPITATION OVER  
WESTERN WASHINGTON AND OREGON IS FORECAST FROM FEB. 25-27 POTENTIALLY RESULTING  
IN 1.5 INCHES OF LIQUID EQUIVALENT OVER 24 HOURS.  
 
SNOW MELT AND HEAVY RAINFALL DURING THE PERIOD IN AREAS THAT HAVE FROZEN GROUND  
MAY CAUSE AREAS OF FLOODING ACROSS PORTIONS OF THE SOUTHERN PLAINS, MISSISSIPPI  
VALLEY, THE OHIO VALLEY AND GREAT LAKES REGION.  
 
AN OCCLUDED FRONTAL SYSTEM IS EXPECTED TO TRACK INTO THE GULF OF ALASKA ON FEB.  
25. THE PREDICTED WIND SPEEDS ASSOCIATED WITH THIS SYSTEM DO NOT APPEAR TO  
JUSTIFY A WIND HAZARD ON THE MAP BUT THERE COULD BE LOCALIZED STRONG GAP WINDS  
THROUGH THE SHELIKOF STRAIT (NEAR KODIAK) AND LOWER COOK INLET. ANOTHER CYCLONE  
IN THE BERING SEA IS LIKELY TO BRING STRONG WINDS TO THE ALEUTIAN ISLANDS AND  
ALASKA PENINSULA ON FEB. 25-26, BUT THESE WILL PROBABLY BE UNDER THE THRESHOLD  
TO WARRANT A SHAPE ON THE MAP.  
 
FOR FRIDAY MARCH 02 - THURSDAY MARCH 08: PERSISTENT TROUGHING OVER THE WESTERN  
U.S. IS EXPECTED TO DOMINATE THE 8-14 DAY TIME PERIOD, LEADING TO A LARGE AREA  
OF HIGH PROBABILITIES OF MUCH BELOW NORMAL TEMPERATURES. MODELS ARE IN GOOD  
AGREEMENT ABOUT COLD AIR IN NORTHERN IDAHO THROUGH MONTANA AND THE DAKOTAS,  
JUSTIFYING AN AREA OF HIGH RISK. MODELS ALSO HINT AT A SLIGHT RISK OF HEAVY  
PRECIPITATION OVER CALIFORNIA FROM MAR. 2-4. IN THE INTERIOR CONUS, SLIGHT  
RISKS OF HEAVY PRECIPITATION ARE FOUND OVER THE UPPER-MIDDLE MISSISSIPPI VALLEY  
FROM MAR. 3-4 AND THE SOUTHEASTERN U.S. FROM MAR. 2-6.  
 
THERE IS A SLIGHT CHANCE OF HEAVY PRECIPITATION OVER WESTERN ALASKA FROM MAR.  
2-3 DUE TO A MEAN STORM TRACK FORECAST TO STEER STORMS INTO THE REGION.  
HOWEVER, MODEL CONFIDENCE IS LOWER THAN IT WAS YESTERDAY, SO THIS WILL BE  
WATCHED CAREFULLY.  
 
THE U.S. DROUGHT MONITOR, VALID ON FEB 20, 2018 INDICATES A SLIGHT DECREASE IN  
THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 18.04% LAST WEEK TO  
17.76% THIS WEEK. A FEW OF THE MORE SUBSTANTIAL REVISIONS MADE TO THE MAP THIS  
WEEK INCLUDE AN INCREASE IN THE D1 COVERAGE OVER OREGON, A DECREASE IN THE D3  
COVERAGE OVER NORTHERN TEXAS AND THE ADDITION OF D3 COVERAGE OVER THE FOUR  
CORNERS REGION.  
 
FORECASTER: KYLE MACRITCHIE  
 

 
 
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