580  
FXUS21 KWNC 192019  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 19 2018  
 
SYNOPSIS: AT THE START OF THE PERIOD, A STATIONARY FRONTAL SYSTEM IS EXPECTED  
TO STRETCH FROM EASTERN TEXAS NORTHEASTWARD ACROSS THE LOWER MISSISSIPPI,  
TENNESSEE AND OHIO VALLEYS TO THE EASTERN GREAT LAKES. COLD SURFACE HIGH  
PRESSURE IS FORECAST OVER THE NORTHWESTERN AND NORTH-CENTRAL PARTS OF THE  
NATION. AREAS OF MID-LEVEL LOW PRESSURE ARE ANTICIPATED TO MOVE ACROSS THE  
NORTHWEST U.S. FEB 23-25. HIGH PRESSURE IS FORECAST OVER THE GULF OF ALASKA  
WHILE FRONTAL SYSTEMS ARE EXPECTED TO CROSS THE ALEUTIANS FEB 22-26. DURING  
WEEK-2, MID-LEVEL LOW PRESSURE IS PREDICTED OVER THE WESTERN U.S., WHILE AREAS  
OF MID-LEVEL HIGH PRESSURE ARE ANTICIPATED OVER WESTERN ALASKA/THE ALEUTIANS  
AND THE EAST-CENTRAL U.S.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN PLAINS, THE LOWER AND MIDDLE  
MISSISSIPPI VALLEYS, THE CENTRAL AND SOUTHERN APPALACHIANS, THE TENNESSEE AND  
OHIO VALLEYS, AND THE GREAT LAKES, THU-SUN, FEB 22-FEB 25.  
 
SEVERE WEATHER POSSIBLE FOR PARTS OF THE SOUTHERN PLAINS, AND LOWER MISSISSIPPI  
AND TENNESSEE VALLEYS, SAT, FEB 24.  
 
HEAVY SNOW FOR PARTS OF THE CASCADES, FRI-SUN, FEB 23-25.  
 
HEAVY SNOW FOR PARTS OF THE BITTERROOTS, NORTHERN ROCKIES, AND BLUE MOUNTAINS,  
SAT-SUN, FEB 24-25.  
 
PERIODS OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE PACIFIC NORTHWEST,  
CALIFORNIA, GREAT BASIN, NORTHERN AND CENTRAL ROCKIES, SOUTHWEST, NORTHERN  
PLAINS, AND UPPER MISSISSIPPI VALLEY, THU-MON, FEB 22-26.  
 
HIGH WINDS FOR PARTS OF COASTAL SECTIONS OF NORTHERN AND CENTRAL CALIFORNIA,  
THU-FRI, FEB 22-23.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF MAINLAND ALASKA, THU, FEB 22.  
 
HIGH WINDS FOR PARTS OF THE ALASKA PENINSULA, SOUTHWESTERN AND SOUTH COASTAL  
MAINLAND ALASKA, KODIAK ISLAND, AND THE KENAI PENINSULA, THU-FRI, FEB 22-23.  
 
PERIODS OF HIGH WINDS FOR PARTS OF THE ALEUTIANS, FRI-SUN, FEB 23-25.  
 
PERIODS OF HIGH SIGNIFICANT WAVE HEIGHTS FOR PARTS OF THE ALEUTIANS, FRI-MON,  
FEB 23-26.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHERN PLAINS, MISSISSIPPI VALLEY,  
THE OHIO VALLEY AND GREAT LAKES.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE WESTERN AND  
NORTH-CENTRAL CONUS, TUE-MON, FEB 27-MAR 5.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE PACIFIC  
NORTHWEST, NORTHERN CALIFORNIA, GREAT BASIN, NORTHERN AND CENTRAL ROCKIES, AND  
NORTHERN AND CENTRAL PLAINS, TUE-MON, FEB 27-MAR 5.  
 
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN ROCKIES  
AND NORTHERN PLAINS, TUE-WED, FEB 27-28.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHERN CALIFORNIA AND THE  
SOUTHWEST, TUE-SAT, FEB 27-MAR 3.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHERN CALIFORNIA AND  
THE SOUTHWEST, TUE-SAT, FEB 27-MAR 3.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS,  
TUE-THU, FEB 27-MAR 1.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS,  
TUE-THU, FEB 27-MAR 1.  
 
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 THURSDAY FEBRUARY 22 - MONDAY FEBRUARY 26: AT THE START OF THE PERIOD, A  
VERY SLOW MOVING FRONTAL SYSTEM IS FORECAST TO STRETCH FROM EAST TEXAS  
NORTHEASTWARD TO THE LOWER MISSISSIPPI, TENNESSEE AND OHIO VALLEYS. AREAS OF  
LOW PRESSURE ARE EXPECTED TO RIPPLE ALONG THE FRONT CAUSING HEAVY RAIN (AMOUNTS  
IN EXCESS OF 1 INCH IN 24 HOURS) ACROSS PORTIONS OF THE SOUTHERN PLAINS, THE  
LOWER AND MIDDLE MISSISSIPPI VALLEYS, THE CENTRAL AND SOUTHERN APPALACHIANS,  
THE TENNESSEE AND OHIO VALLEYS, AND THE GREAT LAKES FEB 22-25. IN ADDITION,  
SEVERE WEATHER IS POSSIBLE FOR PARTS OF THE SOUTHERN PLAINS, AND LOWER  
MISSISSIPPI AND TENNESSEE VALLEYS FEB 24.  
 
SNOW MELT AND HEAVY RAINFALL DURING THE PERIOD ON AREAS THAT HAVE FROZEN GROUND  
LEAD TO POSSIBLE RIVER FLOODING ACROSS PORTIONS OF THE SOUTHERN PLAINS,  
MISSISSIPPI VALLEY, THE OHIO VALLEY AND GREAT LAKES.  
 
AREAS OF HIGH PRESSURE OVER THE GREAT BASIN ARE EXPECTED TO MOVE EASTWARD TO  
THE NORTH-CENTRAL CONUS. OFFSHORE FLOW LEADS TO HIGH WINDS (SPEEDS IN EXCESS OF  
30 KNOTS) FOR PARTS OF COASTAL SECTIONS OF NORTHERN AND CENTRAL CALIFORNIA FEB  
22-23. THE AREAS OF HIGH PRESSURE RESULT IN PERIODS OF MUCH-BELOW NORMAL  
TEMPERATURES (NEGATIVE ANOMALIES OF 20-25 DEGREES F) FOR PARTS OF THE PACIFIC  
NORTHWEST, CALIFORNIA, GREAT BASIN, NORTHERN AND CENTRAL ROCKIES, SOUTHWEST,  
NORTHERN PLAINS, AND UPPER MISSISSIPPI VALLEY FEB 22-26.  
 
AREAS OF MID-LEVEL LOW PRESSURE ARE FORECAST TO CROSS THE NORTHWEST CONUS.  
HEAVY SNOW (AMOUNTS IN EXCESS OF 6 INCHES IN 24 HOURS) IS FORECAST FOR PARTS OF  
THE CASCADES FEB 23-25, AND PARTS OF THE BITTERROOTS, NORTHERN ROCKIES, AND  
BLUE MOUNTAINS FEB 24-25.  
 
HIGH PRESSURE OVER THE GULF OF ALASKA LEADS TO STRONG SOUTHERLY FLOW ACROSS  
MUCH OF THE STATE. MUCH ABOVE NORMAL TEMPERATURES (POSITIVE TEMPERATURE  
ANOMALIES OF 20-30 DEGREES F) ARE EXPECTED ACROSS PORTIONS OF MAINLAND ALASKA  
FEB 22. THE TIGHT PRESSURE GRADIENT BETWEEN THE AREA OF HIGH PRESSURE AND LOW  
PRESSURE OVER THE BERING SEA IS PREDICTED TO CAUSE HIGH WINDS (SPEEDS IN EXCESS  
OF 40 KNOTS) FOR PARTS OF THE ALASKA PENINSULA, SOUTHWESTERN AND SOUTH COASTAL  
MAINLAND ALASKA, KODIAK ISLAND, AND THE KENAI PENINSULA FEB 22-23. A SERIES OF  
FRONTAL SYSTEMS CROSSING THE ALEUTIANS LEADS TO PERIODS OF HIGH WINDS (SPEEDS  
IN EXCESS OF 40 KNOTS) FEB 23-25, AND HIGH SIGNIFICANT WAVE HEIGHTS (IN EXCESS  
OF 20 FEET) FEB 23-26.  
 
FOR TUESDAY FEBRUARY 27 - MONDAY MARCH 05: THE WEEK-2 MID-LEVEL FLOW PATTERN  
ACROSS THE FORECAST DOMAIN IS EXPECTED TO FEATURE A  
 
TROUGH OVER THE WESTERN CONUS AND RIDGES OVER WESTERN ALASKA/THE ALEUTIANS AND  
THE EAST-CENTRAL CONUS. A ROBUST SOUTHERN JET STREAM IS FORECAST ACROSS THE  
SOUTHERN TIER OF THE U.S. BELOW NORMAL HEIGHTS LEAD TO A SLIGHT RISK OF MUCH  
BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE WESTERN AND NORTH-CENTRAL CONUS  
FEB 27-MAR 5, A MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF  
THE PACIFIC NORTHWEST, NORTHERN CALIFORNIA, GREAT BASIN, NORTHERN AND CENTRAL  
ROCKIES, AND NORTHERN AND CENTRAL PLAINS FEB 27-MAR 5, AND A HIGH RISK OF MUCH  
BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN ROCKIES AND NORTHERN PLAINS  
FEB 27-28.  
 
THE TROUGH OVER THE WESTERN CONUS IS EXPECTED TO CAUSE A SLIGHT RISK OF HEAVY  
PRECIPITATION FOR PORTIONS OF SOUTHERN CALIFORNIA AND THE SOUTHWEST FEB 27-MAR  
3, A MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHERN CALIFORNIA  
AND THE SOUTHWEST FEB 27-MAR 3, A SLIGHT RISK OF HEAVY PRECIPITATION FOR  
PORTIONS OF THE SOUTHERN PLAINS FEB 27-MAR 1, AND A MODERATE RISK OF HEAVY  
PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS FEB 27-MAR 1.  
 
 
 
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: RANDY SCHECHTER  
 

 
 
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