021  
FXUS21 KWNC 012120  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST MARCH 01 2018  
 
SYNOPSIS: AREAS OF MID-LEVEL LOW PRESSURE ARE FORECAST TO PLAY A LARGE ROLE  
OVER TO THE CONTIGUOUS U.S. OVER THE NEXT TWO WEEKS, BRINGING AN ACTIVE PERIOD  
FOR MUCH OF THE LOWER 48 FOR THE DAYS 3-7 PERIOD AND MORE LOCALIZED ACTIVITY  
FOR WEEK-2. AN ANOMALOUS MID-LEVEL LOW PRESSURE CENTER IS EXPECTED TO PROPAGATE  
EASTWARD ACROSS THE CONTIGUOUS U.S. DURING WEEK-1, FAVORING DEVELOPMENT OF A  
SURFACE LOW-PRESSURE SYSTEM IN THE WEST. THE ASSOCIATED COLD FRONT WITH THIS  
SYSTEM IS LIKELY TO CAUSE DISTURBANCES AS IT MOVES EASTWARD ACROSS THE CENTRAL  
AND EASTERN U.S. AS THE MID-LEVEL LOW PRESSURE MOVES OUT THE WEST, SURFACE  
HIGH-PRESSURE IS LIKELY TO FILL THE AREA, BRINGING COLDER AIR FROM CANADA  
SOUTHWARD. FOR WEEK-2, MID-LEVEL LOW PRESSURE OFF THE WESTERN COAST IS LIKELY  
TO BRING AN UNSETTLED PATTERN TO CALIFORNIA AND THE COAST. ALASKA IS FORECAST  
TO EXPERIENCE A SERIES OF SURFACE LOW PRESSURE SYSTEMS IN DAYS 3-7, THOUGH NONE  
THAT ARE LIKELY TO BE VERY IMPACTFUL. FOR WEEK-2, A MID-LEVEL LOW PRESSURE  
SYSTEM IS EXPECTED TO MOVE OVER THE MAINLAND AND REMAIN THROUGHOUT THE WEEK.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY AND THE SOUTHERN  
PLAINS, MON-TUE, MAR 5-MAR 6.  
 
HEAVY SNOW ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS, SUN-MON, MAR 4-MAR 5.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHEAST, THE GREAT LAKES, THE OHIO  
VALLEY, AND THE TENNESSEE VALLEY.  
 
FLOODING OCCURRING OR IMMINENT 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.  
 
HIGH WINDS ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE CENTRAL ROCKIES, THE  
SOUTHERN PLAINS, AND THE CENTRAL PLAINS, SUN-MON, MAR 4-MAR 5.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF CALIFORNIA, THE CENTRAL GREAT  
BASIN, THE PACIFIC NORTHWEST, THE NORTHERN GREAT BASIN, AND THE SOUTHWEST,  
SUN-TUE, MAR 4-MAR 6.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE ROCKIES, THE CENTRAL  
PLAINS, THE NORTHERN PLAINS, SUN-WED, MAR 4-MAR 7.  
 
ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE CENTRAL  
PLAINS, AND THE SOUTHERN PLAINS, SUN, MAR 4.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF MAINLAND ALASKA, MON-WED, MAR  
5-MAR 7.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHEAST,  
THE MID-ATLANTIC, THE SOUTHERN APPALACHIANS, AND THE TENNESSEE VALLEY, FRI-SAT,  
MAR 9-MAR 10.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE ALASKA  
PANHANDLE AND MAINLAND ALASKA, SUN-THU, MAR 11-MAR 15.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF MAINLAND  
ALASKA, MON-WED, MAR 12-MAR 14.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA, THE CENTRAL  
GREAT BASIN, THE PACIFIC NORTHWEST, THE NORTHERN GREAT BASIN, AND THE  
SOUTHWEST, FRI-TUE, MAR 9-MAR 13.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL GREAT BASIN,  
CALIFORNIA, AND THE SOUTHWEST, FRI-SUN, MAR 9-MAR 11.  
 
SEVERE DROUGHT ACROSS THE CENTRAL PLAINS, THE CENTRAL ROCKIES, THE CENTRAL  
GREAT BASIN, THE NORTHERN PLAINS, THE SOUTHERN ROCKIES, CALIFORNIA, THE  
SOUTHERN PLAINS, AND THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR SUNDAY MARCH 04 - THURSDAY MARCH 08: THE WEEK-1 PERIOD IS FORECAST TO BE AN  
ACTIVE PERIOD, SPECIFICALLY IN THE WESTERN AND CENTRAL CONUS. A 500-HPA TROUGH  
IS EXPECTED TO BUILD INTO THE NORTHWESTERN CONUS. AT THE BEGINNING OF THE  
PERIOD AND PROPAGATE EASTWARD THROUGH DAY 7. A SECOND TROUGH IS LIKELY TO PUSH  
SOUTH OVER THE GREAT LAKES REGION IN THE MIDDLE OF THE PERIOD, COMBINING WITH  
THE FIRST TROUGH, AND PROPAGATING EASTWARD. LEE CYCLOGENESIS IS FORECAST OVER  
THE CENTRAL PLAINS NEAR THE START OF THE FORECAST PERIOD. THE SURFACE LOW  
PRESSURE SYSTEM IS EXPECTED TO DEEPEN SLIGHTLY AS IT MOVES INTO THE UPPER  
MIDWEST AND GREAT LAKES REGION. A RISK FOR HEAVY SNOW (ABOVE 6 INCHES IN 24  
HOURS) HAS BEEN FORECAST FOR PARTS OF THE UPPER MIDWEST AND NORTH CENTRAL  
PLAINS ASSOCIATED WITH THE ADVANCING COLD FRONT FOR MARCH 3-4. AS THE SURFACE  
SYSTEM CONTINUES TO MOVE EASTWARD, HEAVY RAIN IS POSSIBLE IN THE LOWER  
MISSISSIPPI RIVER VALLEY FOR MARCH 5-6. MODEL GUIDANCE IS UNCERTAIN ON THE  
ONSET OF THIS EVENT, THOUGH ECMWF AND GFS MODELS SUPPORT 24 HOUR TOTALS OVER 1  
INCH. RISK FOR THIS AREA IS HIGHLIGHTED DUE TO RECENT FLOODING CONCERNS.  
 
ALSO IN ASSOCIATION WITH THE MID-LEVEL TROUGH IS THE POTENTIAL FOR ENHANCED  
RISK OF FIRE WEATHER OVER THE SOUTHERN AND CENTRAL PLAINS ON MARCH 4 AND HIGH  
WINDS (30 KNOTS OR GREATER) ACROSS A SIMILAR REGION ON THE 4TH AND 5TH. WITH  
THIS SETUP, STRONG MID-LEVEL FLOW IS LIKELY TO BE MIXED DOWN TO THE SURFACE,  
COUPLED WITH LOCALIZED DOWNSLOPE EFFECTS TO FURTHER DECREASE LOW-LEVEL HUMIDITY  
AND RAISE TEMPERATURES. THIS SETUP FAVORS WARM, DRY CONDITIONS CONDUCIVE FOR  
FIRE POTENTIAL ON THE 4TH. AS THE SURFACE SYSTEM MOVES NORTHEAST ON MARCH 5,  
THE HIGH WINDS ARE FORECAST TO EXTEND INTO NEBRASKA AND KANSAS.  
 
FOLLOWING THE PATH OF THE MID-LEVEL TROUGH, COLD AIR IS LIKELY TO DESCEND FROM  
CANADA INTO THE WEST. TWO REGIONS HAVE BEEN HIGHLIGHTED FOR MUCH BELOW NORMAL  
TEMPERATURES; THE GREAT BASIN FOR MARCH 4-6 AND THE NORTHERN PLAINS FOR MARCH  
4-7. TEMPERATURES ANOMALIES ARE FORECAST TO BE THE GREATEST ON THE 5TH, OVER  
-20 DEGREES F. HOWEVER, AS OFFSHORE MID-LEVEL TROUGH BEGINS TO MOVE TOWARD THE  
COAST, THE COLD AIR IS EXPECTED TO RETREAT FROM THE GREAT BASIN ON THE 6TH,  
WHILE CONTINUING OVER THE NORTHERN PLAINS THROUGH THE 7TH.  
 
ALASKA IS FORECAST TO BE IMPACTED BY MULTIPLE SURFACE DISTURBANCES IN THE  
BERING SEA AND GULF OF ALASKA, WITH EACH SYSTEM RELATIVELY WEAK BY ALASKAN  
STANDARDS. GIVEN THE MODEST INTENSITIES FORECAST FOR EACH OF THESE SYSTEMS, NO  
PRECIPITATION, WIND, OR WAVE HAZARDS ARE CURRENTLY ANTICIPATED. MUCH ABOVE  
NORMAL TEMPERATURES ARE LIKELY FOR NORTHERN ALASKA FOR MARCH 5-7 (TEMPERATURE  
ANOMALIES GREATER THAN 40 DEGREES F).  
 
FOR FRIDAY MARCH 09 - THURSDAY MARCH 15: THE WEEK-2 PERIOD IS FORECAST TO BEGIN  
WITH SOME MID-LEVEL ACTIVITY AND STABILIZE INTO A MUCH QUIETER PATTERN  
MID-WEEK. THE PREVIOUSLY DISCUSSED 500-HPA TROUGH IS EXPECTED TO PASS OVER THE  
EASTERN HALF OF THE CONUS AT THE BEGINNING OF THE PERIOD. A SLIGHT RISK FOR  
MUCH BELOW NORMAL TEMPERATURE HAS BEEN POSTED FOR THE SOUTHEAST, WITH  
TEMPERATURE ANOMALIES OF 12 DEGREES F, FOR MARCH 9-10. FOR PARTS OF THE  
SOUTHEAST, A LATE FREEZE IS POSSIBLE DOWN INTO NORTHERN GEORGIA AND ALABAMA.  
THE CALIBRATED GEFS SUPPORTS AT LEAST A 20% CHANCE FOR PARTS OF THE HIGHLIGHTED  
REGION TO DROP BELOW 40 DEGREES F, WHILE ALSO GIVING A 20% CHANCE OF THE AREA  
BEING BELOW THE 15TH CLIMATOLOGICAL PERCENTILE ON THESE DATES.  
 
ANOMALOUS MID-LEVEL TROUGHING IS FORECAST OFF THE WESTERN COAST OF THE CONUS  
FOR MUCH OF THE WEEK-2 PERIOD. THIS SCENARIO FAVORS UNSETTLED WEATHER FOR MUCH  
OF THE WEST COAST, PARTICULARLY ACROSS CALIFORNIA. A MODERATE RISK OF HEAVY  
PRECIPITATION IS FORECAST FOR MUCH OF NORTHERN CALIFORNIA FOR MARCH 9-10, WITH  
A BROADER REGION OF A SLIGHT RISK OF HEAVY PRECIPITATION FOR THE CENTRAL AND  
SOUTHERN WEST COAST FROM MARCH 9-12. MODEL GUIDANCE SHOWS DISAGREEMENT IN THE  
ONSET OF THIS EVENT. THE CALIBRATED ECMWF SOLUTION SHOWS AN EARLIER ONSET FOR  
THE 9TH AND 10TH, WHILE THE BULK OF PRECIPITATION IN THE GEFS IS SEEN ON THE  
10TH AND 11TH. BOTH MODELS SHOW LOCALIZED AREAS HAVING A GREATER THAN 60%  
CHANCE OF EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE OF PRECIPITATION AT THE  
PEAK OF THE EVENT. ACROSS THE MODERATE RISK AREA DAILY ENSEMBLE MEAN LIQUID  
EQUIVALENT TOTALS ARE GENERALLY AROUND AN INCH FROM BOTH THE GFS AND ECMWF,  
WITH LOCALLY HIGHER VALUES UP TO 2.5 INCHES IN A DAY FROM THEIR DETERMINISTIC  
RUNS.  
 
A MID-LEVEL TROUGH OVER ALASKA IS LIKELY TO BRING MUCH BELOW-NORMAL  
TEMPERATURES TO THE MAINLAND FOR MUCH OF THE WEEK-2 PERIOD. A SLIGHT RISK HAS  
BEEN HIGHLIGHTED FOR MAR 11-15, WITH A MODERATE RISK FOR WESTERN MAINLAND  
ALASKA FOR MAR 12-14. ENSEMBLE MEAN TEMPERATURE ANOMALIES IN THE MODERATE RISK  
AREA APPEAR ON TRACK TO EXCEED -16 DEGREES F, WHILE THE CALIBRATED GEFS GIVES A  
40% CHANCE OF MINIMUM TEMPERATURES BEING BELOW THE 15TH CLIMATOLOGICAL  
PERCENTILE.  
 
THE U.S. DROUGHT MONITOR, VALID ON FEB 27, 2018 INDICATES A DECREASE IN THE  
COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 17.76% LAST WEEK TO  
14.31% THIS WEEK. A FEW OF THE MORE SUBSTANTIAL REVISIONS MADE TO THE MAP THIS  
WEEK INCLUDE A DECREASE IN THE D1 COVERAGE OVER PENNSYLVANIA AND A DECREASE IN  
THE D2 COVERAGE OVER OKLAHOMA AND ARKANSAS.  
 
FORECASTER: CHRISTINA FINAN  
 

 
 
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