601  
FXUS21 KWNC 061920  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST FEBRUARY 06 2018  
 
SYNOPSIS: A COLD FRONT IS FORECAST TO SLOWLY PUSH SOUTHEAST ACROSS THE EASTERN  
U.S. THIS WEEKEND WITH SURFACE HIGH PRESSURE SHIFTING SOUTH FROM CANADA. DURING  
THE EARLY PART OF WEEK-2, AN AREA OF MID-LEVEL LOW PRESSURE IS EXPECTED TO  
DEVELOP OVER THE WESTERN U.S., WHILE AN AREA OF MID-LEVEL HIGH PRESSURE  
STRENGTHENS OVER THE GULF OF MEXICO, FLORIDA, AND SOUTHWEST ATLANTIC. MULTIPLE  
SURFACE LOW PRESSURE SYSTEMS ARE FORECAST TO ENTER THE BERING SEA AND AFFECT  
THE ALEUTIANS AND SOUTHWESTERN MAINLAND ALASKA THROUGH MID-FEBRUARY.  
 
HAZARDS  
 
MUCH BELOW-NORMAL TEMPERATURES FOR THE NORTHERN AND CENTRAL GREAT PLAINS,  
FRI-SAT, FEB 9-10.  
 
HEAVY SNOW FOR PARTS OF THE CENTRAL ROCKIES, FRI-SAT, FEB 9-10.  
 
HEAVY RAIN FOR PARTS OF THE SOUTHEAST, FRI-SAT, FEB 9-10.  
 
HIGH WINDS ACROSS PORTIONS OF SOUTHWEST ALASKA AND THE ALEUTIANS, FRI-SAT, FEB  
9-10.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND  
IDAHO.  
 
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE NORTHERN HIGH PLAINS  
AND NORTHERN ROCKIES, WED-TUE, FEB 14-20.  
 
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN AND  
CENTRAL GREAT PLAINS, NORTHERN ROCKIES, AND PACIFIC NORTHWEST, WED-TUE, FEB  
14-20.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE LOWER TO MIDDLE MISSISSIPPI  
VALLEY, OHIO VALLEY, AND TENNESSEE VALLEY, WED-TUE, FEB 14-20.  
 
SEVERE DROUGHT ACROSS PARTS OF CALIFORNIA, THE CENTRAL AND SOUTHERN  
INTERMOUNTAIN REGION, THE CENTRAL AND SOUTHERN ROCKIES, THE GREAT PLAINS, THE  
MIDDLE AND LOWER MISSISSIPPI VALLEY, THE SOUTHEAST, AND THE MID-ATLANTIC.  
 
DETAILED SUMMARY  
 
FOR FRIDAY FEBRUARY 09 - TUESDAY FEBRUARY 13: AN ARCTIC SURFACE FRONT IS  
FORECAST TO PROGRESS SOUTH ACROSS THE GREAT PLAINS ON FEB 9 AND 10 WITH A 1036  
TO 1040-HPA SURFACE HIGH BUILDING OUT OF CANADA. MUCH BELOW-NORMAL TEMPERATURES  
(NEGATIVE DAILY ANOMALIES OF 20 TO 30 DEGREES F) ACROSS THE NORTHERN AND  
CENTRAL GREAT PLAINS ARE EXPECTED TO ACCOMPANY THE SURFACE HIGH ON FEB 9 AND  
10. UPSLOPE FLOW BEHIND THE FRONT IS LIKELY TO BRING MODERATE TO HEAVY SNOW (4  
TO 8 INCHES) ACROSS THE FRONT RANGE OF THE CENTRAL ROCKIES ON FEB 9 AND 10. A  
LOW PRESSURE SYSTEM MAY TRACK EAST ACROSS THE CENTRAL GREAT PLAINS AND MIDWEST  
THIS WEEKEND, BUT SNOWFALL AMOUNTS ASSOCIATED WITH THIS LOW PRESSURE SYSTEM  
REMAIN HIGHLY UNCERTAIN DUE TO POOR MODEL CONTINUITY.  
 
A COLD FRONT WITH WAVES OF LOW PRESSURE IS FORECAST TO PUSH SLOWLY SOUTHEAST  
FROM THE CENTRAL U.S. ON FEB 9 TO OFFSHORE OF THE EAST COAST BY FEB 12.  
MODERATELY STRONG INFLOW FROM THE GULF OF MEXICO COUPLED WITH THE SLOW-MOVING  
FRONT IS LIKELY TO BRING HEAVY RAIN (1 TO 3 INCHES) TO THE TENNESSEE VALLEY AND  
SOUTHERN APPALACHIANS ON FEB 9 AND 10. MODERATE RAINFALL AMOUNTS OF 0.5 TO 1.0  
INCH ARE FORECAST ACROSS THE REMAINDER OF THE SOUTHEAST AND MID-ATLANTIC THIS  
WEEKEND.  
 
THE GFS AND ECMWF MODELS INDICATE A SURFACE LOW (AROUND 972-HPA) NEAR THE  
ALEUTIANS AND A 1042-HPA SURFACE HIGH OVER NORTHWEST CANADA LATER THIS WEEK. A  
TIGHT PRESSURE GRADIENT IS LIKELY TO PROMOTE HIGH WINDS (SPEEDS OF 40 KNOTS OR  
HIGHER) ACROSS THE ALEUTIANS, ALASKA PENINSULA, KODIAK ISLAND, AND SOUTHWEST  
MAINLAND ALASKA ON FEB 9 AND 10. WAVE HEIGHTS ARE EXPECTED TO REMAIN BELOW THE  
HAZARDOUS THRESHOLD.  
 
FOR WEDNESDAY FEBRUARY 14 - TUESDAY FEBRUARY 20: THE ENSEMBLE MEANS SEEM TO BE  
CONVERGING ON A 500-HPA LONGWAVE PATTERN DURING MID-FEBRUARY THAT FEATURES AN  
AMPLIFYING TROUGH EXTENDING FROM NEAR HUDSON BAY SOUTHWEST TO THE NORTHERN  
ROCKIES AND NORTHERN PLAINS WITH A STRONG SUBTROPICAL RIDGE CENTERED OVER THE  
GULF OF MEXICO AND FLORIDA. DESPITE THE CONVERGING MODEL SOLUTIONS AMONG  
ENSEMBLE MEANS, FORECAST CONFIDENCE DURING WEEK-2 REMAINS TEMPERED BY MODERATE  
TO LARGE SPREAD AMONG THE GFS AND ECMWF MEMBERS.  
 
THE DETERMINISTIC GFS AND ECMWF MODEL RUNS FAVOR ANOTHER OUTBREAK OF ARCTIC AIR  
ENTERING THE NORTHERN GREAT PLAINS EARLY IN WEEK-2. THE GEFS TEMPERATURE TOOL  
INDICATES THAT MINIMUM TEMPERATURES HAVE A 50 TO 60 PERCENT OF FALLING BELOW  
THE 15TH CLIMATOLOGICAL PERCENTILE ACROSS THE NORTHERN GREAT PLAINS ON FEB 15.  
BASED ON THE EVOLVING LONGWAVE PATTERN AND TEMPERATURE GUIDANCE FROM THE GEFS,  
A SLIGHT TO MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES IS POSTED  
THROUGHOUT WEEK-2 FOR PARTS OF THE PACIFIC NORTHWEST, NORTHERN ROCKIES, AND  
NORTHERN AND CENTRAL GREAT PLAINS. ALTHOUGH PERIODS OF UPSLOPE SNOW ARE LIKELY  
TO AFFECT THE NORTHERN HIGH PLAINS DURING MID-FEBRUARY, SNOWFALL AMOUNTS ARE  
EXPECTED TO REMAIN BELOW HAZARDS CRITERIA.  
 
AN INCREASING THERMAL GRADIENT IS EXPECTED TO DEVELOP FROM THE HIGHER LATITUDES  
OF NORTH AMERICA TO THE GULF COAST DURING WEEK-2. SHORTWAVE TROUGHS EMBEDDED  
WITHIN SOUTHWEST FLOW ALOFT ALONG WITH MORE PERSISTENT FLOW FROM THE GULF OF  
MEXICO SUPPORT AT LEAST A SLIGHT RISK OF HEAVY PRECIPITATION OVER THE OHIO AND  
TENNESSEE VALLEYS THROUGH WEEK-2.  
 
THE U.S. DROUGHT MONITOR, VALID ON JANUARY 30, 2018 INDICATES A SUBSTANTIAL  
INCREASE IN THE COVERAGE OF SEVERE TO EXCEPTIONAL DROUGHT (D2-D4) FROM 13.60%  
LAST WEEK TO 17.21% THIS WEEK. DRYNESS AND DROUGHT HAVE INCREASED IN SPATIAL  
COVERAGE AND/OR INTENSIFIED OVER PORTIONS OF CALIFORNIA AND THE SOUTHWEST THIS  
WEEK. SOME DETERIORATION IN CONDITIONS IS ALSO NOTED OVER THE SOUTHERN PLAINS.  
 
FORECASTER: BRAD PUGH  
 

 
 
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