789  
FXUS21 KWNC 021957  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST MARCH 02 2018  
 
SYNOPSIS: AN ACTIVE PATTERN IS PREDICTED DURING THE TWO WEEK PERIOD FOR MUCH OF  
THE LOWER 48 STATES. A MID-LEVEL LOW PRESSURE CENTER IS EXPECTED TO IMPACT THE  
CENTRAL AND EASTERN U.S. DURING DAYS 3-7. SURFACE LOW PRESSURE AND AN  
ASSOCIATED COLD FRONT ARE LIKELY TO BRING UNSETTLED WEATHER TO A FEW REGIONS  
THROUGHOUT THE PERIOD. THE WEEK-2 PERIOD IS FORECAST TO BE CHARACTERIZED BY TWO  
MID-LEVEL LOW PRESSURE CENTERS MOVING QUICKLY EASTWARD. SEVERAL STORM SYSTEMS  
ARE EXPECTED OVER ALASKA FOR WEEK-1 BEFORE MID-LEVEL LOW PRESSURE MOVES OVER  
THE MAINLAND, GIVING WAY TO COOLER TEMPERATURES.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHEAST AND THE GREAT LAKES,  
WED-THU, MAR 7-MAR 8.  
 
HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE LOWER MISSISSIPPI VALLEY, THE  
SOUTHERN PLAINS, AND THE TENNESSEE VALLEY, MON-TUE, MAR 5-MAR 6.  
 
HEAVY SNOW ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND THE NORTHERN  
PLAINS, MON, MAR 5.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHEAST.  
 
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.  
 
FLOODING LIKELY ACROSS PORTIONS OF THE GREAT LAKES.  
 
HIGH WINDS ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE NORTHERN PLAINS, MON,  
MAR 5.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL AND NORTHERN  
PLAINS, THE GREAT BASIN AND THE NORTHERN ROCKIES, MON-WED, MAR 5-MAR 7.  
 
MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF NORTHERN ALASKA, MON-WED, MAR  
5-MAR 7.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHEAST,  
SAT, MAR 10.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE ALASKA  
PANHANDLE, MAINLAND ALASKA, AND THE ALEUTIANS, MON-FRI, MAR 12-MAR 16.  
 
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF SOUTHERN  
ALASKA, SAT-THU, MAR 10-MAR 15.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA, THE WEST COAST  
AND THE GREAT BASIN, SAT-MON, MAR 10-MAR 12.  
 
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA, SAT-SUN, MAR  
10-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 MONDAY MARCH 05 - FRIDAY MARCH 09: A 500-HPA TROUGH IS FORECAST TO MOVE  
EASTWARD OVER THE CENTRAL AND EASTERN CONUS THROUGH THE DAY 3-7 PERIOD, GIVING  
WAY TO AN IMPACTFUL SURFACE LOW PRESSURE SYSTEM MOVING THROUGH THE SAME  
REGIONS. THE WESTERN CONUS IS LIKELY TO EXPERIENCE MID-LEVEL RIDGING AND  
SURFACE HIGH PRESSURE IN THE WAKE OF THE MID-LEVEL TROUGH THAT WILL HAVE  
VACATED THE WESTERN CONUS PRIOR TO THE BEGINNING OF THIS PERIOD. COLD AIR FROM  
CANADA IS EXPECTED TO DESCEND INTO THE WESTERN US AT THE START OF WEEK-1,  
BRINGING MUCH BELOW NORMAL TEMPERATURES (ANOMALIES GREATER THAN -20 DEGREES F)  
TO THE GREAT BASIN AND PARTS OF THE NORTHERN PLAINS FOR MARCH 5-7, WITH THE  
COLDEST ANOMALIES IN THE GREAT BASIN ON THE 5TH AND 6TH. THERE COULD BE SOME  
RESIDUAL COLD TEMPERATURES OVER THE NORTHERN PLAINS FOR MARCH 8, BUT MOST OF  
THE COLDER AIR WILL HAVE MOVED OUT OF THE AREA BY THAT POINT.  
 
IN ASSOCIATION WITH THE MID-LEVEL TROUGH, THERE IS A POTENTIAL FOR HIGH WINDS  
(30KTS OR GREATER) ACROSS THE CENTRAL PLAINS FOR MARCH 5. THE ENHANCED RISK OF  
FIRE WEATHER OVER THIS REGION HAS BEEN POSTED PREVIOUS TO THIS PERIOD; HOWEVER,  
LOW RELATIVE HUMIDITY AND STRONG MID-LEVEL FLOW IS STILL LIKELY OVER THIS  
REGION FOR MARCH 5.  
 
THE AFOREMENTIONED SURFACE LOW PRESSURE SYSTEM IS FORECAST TO FORM OVER THE  
CENTRAL PLAINS AT THE BEGINNING OF THE PERIOD AND PROPAGATE EASTWARD TOWARD THE  
GREAT LAKES, AND THEN MOVE OVER THE NORTHEAST DURING WEEK-1. THIS SYSTEM IS NOT  
FORECAST TO BE PARTICULARLY STRONG (994-HPA OVER THE CENTRAL PLAINS), THOUGH IT  
MAY INTENSIFY AS IT MOVES ALONG THE NORTHEAST; HOWEVER, IT IS EXPECTED TO BRING  
PRECIPITATION TO SEVERAL REGIONS ALONG ITS PATH. A HEAVY SNOW (ABOVE 6 INCHES  
IN 24 HOURS) THREAT HAS BEEN POSTED OVER THE NORTHERN PLAINS, CONCENTRATING IN  
THE DAKOTAS, FOR MARCH 5, AS THE ASSOCIATED COLD FRONT PASSES THROUGH THE  
REGION. AS THE SURFACE SYSTEM CONTINUES TO MOVE EASTWARD, HEAVY RAIN IS  
POSSIBLE IN THE LOWER MISSISSIPPI RIVER VALLEY FOR MARCH 5-6. BOTH THE ECMWF  
AND GFS MODELS SUPPORT 24 HOUR TOTALS OVER 1 INCH AND NOW ARE IN AGREEMENT  
ABOUT THE TIMING OF THIS EVENT. RISK FOR THIS AREA IS HIGHLIGHTED DUE TO RECENT  
FLOODING CONCERNS. TOWARD THE END OF THE PERIOD, THE SAME SYSTEM IS FORECAST TO  
BRING HEAVY PRECIPITATION TO THE NORTHEAST FOR MARCH 7-8. MOST OF THIS IS  
LIKELY TO BE SNOW (5 INCHES IN 24 HOURS), WITH SOME RAIN OR MIXED PRECIPITATION  
(EXCEEDING 1 INCH LIQUID EQUIVALENT IN 24 HOURS) ALONG THE COAST.  
 
A SERIES OF SURFACE LOW PRESSURE SYSTEMS ARE LIKELY TO IMPACT ALASKA OVER THE  
WEEK-1 PERIOD, THOUGH MOST IMPACTS ARE EXPECTED TO STAY BELOW HAZARDOUS  
THRESHOLDS. THE EXCEPTION WOULD BE A STRONG LOW PRESSURE SYSTEM THAT IS  
EXPECTED TO INTENSIFY (968-HPA HEIGHTS) AS IT MOVES OVER SOUTHWEST ALASKA ON  
MARCH 9-10. HIGH WINDS ARE POSSIBLE ON MARCH 9 AS THIS SYSTEM MOVES OVER  
SOUTHERN ALASKA AND PARTS OF THE ALEUTIANS, THOUGH ARE LIKELY TO REMAIN BELOW  
HAZARDOUS CRITERIA. MUCH ABOVE NORMAL TEMPERATURES ARE EXPECTED TO CONTINUE  
OVER NORTHERN ALASKA FOR MARCH 6-7. ANOMALIES ARE LIKELY TO REACH 40 DEGREES F  
OR GREATER.  
 
FOR SATURDAY MARCH 10 - FRIDAY MARCH 16: A FEW SHORTWAVE MID-LEVEL TROUGHS ARE  
EXPECTED TO MOVE ACROSS THE CONUS DURING WEEK-2. MUCH BELOW NORMAL TEMPERATURES  
ARE EXPECTED IN THE SOUTHEAST AT THE BEGINNING OF THE PERIOD, IN THE WAKE OF  
THE 500-HPA TROUGH FROM WEEK-1. A SLIGHT RISK HAS BEEN FORECAST FOR THE REGION  
FOR MARCH 10. FOR PARTS OF THE SOUTHEAST (SOUTH CAROLINA, GEORGIA AND ALABAMA),  
A LATE FREEZE IS POSSIBLE. THE GEFS REFORECAST TOOL SUPPORTS 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 THIS  
DATE (40% FOR PARTS OF FLORIDA). FLORIDA IS EXPECTED TO STAY WELL ABOVE  
FREEZING, WITH MOST OF THE PENINSULA STAYING ABOVE 50 DEGREES F, SO ONLY A  
SLIGHT RISK IS POSTED AT THIS TIME. A SECOND 500-HPA TROUGH IS FORECAST TO MOVE  
OVER THE CONUS THROUGH WEEK-2, WITH SOME ASSOCIATED LEE CYCLOGENESIS LIKELY AT  
THE BEGINNING OF THE PERIOD. THE SURFACE SYSTEM IS FORECAST TO QUICKLY  
PROPAGATE EASTWARD, POSSIBLY CAUSING SOME HEAVY RAIN ALONG THE LOWER  
MISSISSIPPI RIVER VALLEY. MODEL GUIDANCE IS IN DISAGREEMENT OVER THIS SYSTEM,  
WITH THE ECMWF FORECASTING A MUCH STRONGER EVENT THAN THE GEFS. DUE TO THIS  
DISPARITY, THE RISK REMAINS OFF THE HAZARDS MAP AT THIS TIME.  
 
ANOMALOUS MID-LEVEL TROUGHING OFF THE WEST COAST IS LIKELY TO BRING UNSETTLED  
WEATHER TO THE REGION, PARTICULARLY CALIFORNIA, DURING WEEK-2. A MODERATE RISK  
OF HEAVY PRECIPITATION IS FORECAST FOR PARTS OF NORTHERN CALIFORNIA FOR MARCH  
10-11, WITH A BROADER REGION OF A SLIGHT RISK ALONG THE CENTRAL AND SOUTHERN  
WEST COAST FROM MARCH 10-12. THE ENSEMBLE FORECASTS HAVE WEAKENED ON THE  
IMPACTS OF THIS SYSTEM WHEN COMPARED WITH YESTERDAY'S MODEL GUIDANCE, WITH  
ENSEMBLE MEAN LIQUID EQUIVALENT TOTALS UNDER 1 INCH IN 24 HOURS. HOWEVER, THE  
DETERMINISTIC MODELS CONTINUE TO SHOW UP TO 2.5 INCHES OF PRECIPITATION IN 24  
HOURS FOR PARTS OF CENTRAL AND NORTHERN CALIFORNIA.  
 
A MID-LEVEL TROUGH OVER ALASKA IS LIKELY TO BRING MUCH BELOW-NORMAL  
TEMPERATURES TO THE MAINLAND AND PARTS OF THE PANHANDLE FOR THE WEEK-2 PERIOD.  
A SLIGHT RISK HAS BEEN HIGHLIGHTED FOR MAR 10-16, WITH A MODERATE RISK FOR  
SOUTHWESTERN MAINLAND ALASKA FOR MAR 10-15. ENSEMBLE MEAN TEMPERATURE ANOMALIES  
IN THE MODERATE RISK AREA APPEAR ON TRACK TO EXCEED -20 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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