606  
FXUS21 KWNC 272133  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EST NOVEMBER 27 2017  
 
SYNOPSIS: AT THE START OF THE PERIOD, LOW-PRESSURE IS EXPECTED TO MOVE ACROSS  
THE GREAT LAKES AND NORTHEAST, WITH ANOTHER LOW-PRESSURE SYSTEM PREDICTED TO  
IMPACT THE PACIFIC NORTHWEST. THAT SYSTEM FROM THE PACIFIC NORTHWEST IS  
FORECAST TO MOVE TO THE ROCKIES AND EVENTUALLY THE CENTRAL GREAT PLAINS. HIGH  
PRESSURE IS FORECAST OVER THE U.S., EAST OF THE MISSISSIPPI RIVER, FOR MUCH OF  
THE PERIOD. A DEEP AND PERSISTENT LOW-PRESSURE SYSTEM IS FORECAST WEST OF  
ALASKA, WITH SMALLER IMPULSES WRAPPING ABOUT THE MAIN SYSTEM, WITH IMPACTS  
MAINLY OVER THE ALEUTIANS, SOUTHERN ALASKA, AND THE ALASKA PANHANDLE.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THU, NOV 30.  
 
HEAVY SNOW ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND THE NORTHERN GREAT  
BASIN, THU, NOV 30.  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF CALIFORNIA, THE CENTRAL AND NORTHERN  
GREAT BASIN, AND THE PACIFIC NORTHWEST, SAT-SUN, DEC 2-DEC 3.  
 
HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN PLAINS, THE NORTHERN ROCKIES, AND  
THE NORTHERN GREAT BASIN, SAT, DEC 2.  
 
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES AND THE CENTRAL GREAT BASIN,  
SUN, DEC 3.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE PACIFIC NORTHWEST.  
 
HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE LOWER AND MIDDLE MISSISSIPPI  
VALLEYS, THE OHIO VALLEY, AND THE TENNESSEE VALLEY, TUE-WED, DEC 5-DEC 6.  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE ALASKA PANHANDLE AND MAINLAND  
ALASKA, SUN-MON, DEC 3-DEC 4.  
 
HIGH WINDS ACROSS PORTIONS OF MAINLAND ALASKA AND THE ALEUTIANS, THU-FRI, NOV  
30-DEC 1.  
 
HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF MAINLAND ALASKA AND THE  
ALEUTIANS, THU, NOV 30.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL AND  
SOUTHERN ROCKIES, THE CENTRAL GREAT BASIN, CALIFORNIA, THE SOUTHERN PLAINS, AND  
THE SOUTHWEST, TUE-WED, DEC 5-DEC 6.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FROM THE SOUTHERN GREAT PLAINS TO  
THE SOUTHEAST AND CAROLINAS, SAT-MON, DEC 9-DEC 11.  
 
SEVERE DROUGHT ACROSS THE LOWER MISSISSIPPI VALLEY, THE NORTHERN PLAINS,  
HAWAII, THE NORTHERN ROCKIES, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN  
PLAINS, AND THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR THURSDAY NOVEMBER 30 - MONDAY DECEMBER 04: A LOW-PRESSURE SYSTEM IS  
FORECAST OVER THE GREAT LAKES AND NORTHEAST, WITH SOME WIDE RANGING IMPACTS.  
OVER THE GREAT LAKES, WINDS ARE FORECAST TO BE APPROXIMATELY 30 KNOTS. SOME  
LAKE ENHANCED PRECIPITATION IS FORECAST, BUT TEMPERATURES ARE FORECAST TO BE  
NEAR TO JUST SLIGHTLY BELOW FREEZING, SO LARGE ACCUMULATIONS ARE NOT PREDICTED.  
SOME HIGHER (LIKELY IN EXCESS OF 40 MPH) WINDS ARE PREDICTED OVER THE HIGHER  
TERRAIN OF THE NORTHEAST BY FRIDAY, AND EASTERN MAINE BY SATURDAY NIGHT. NO  
HAZARD IS SPECIFICALLY DEPICTED AS THE THREAT IS LIKELY TO BE ISOLATED TO THE  
HIGHEST TERRAIN, AND THERE IS MODEL DISAGREEMENT, EVEN AT THE SHORT LEAD TIME.  
ALONG THE SOUTHERN END OF THE ASSOCIATED COLD FRONT, HIGH WINDS AND MARGINAL  
CONDITIONS FOR CRITICAL FIRE WEATHER ARE POSSIBLE, THURSDAY, OVER THE SOUTHERN  
PLAINS.  
 
OVER THE WESTERN CONUS, A TROUGH MOVING IN BY THE WEEKEND IS LIKELY TO BRING  
HEAVY PRECIPITATION TO THE PACIFIC NORTHWEST, WITH HEAVY SNOWS IN THE CASCADES.  
THROUGH THE WEEKEND, THE HEAVY PRECIPITATION THREAT IS FORECAST TO SHIFT TO  
OREGON AND NORTHERN CALIFORNIA AS THE TROUGH IS PREDICTED TO DIG SOUTHWARD  
ALONG THE WEST COAST. CORRESPONDINGLY, THE HEAVY SNOWFALL THREAT SHIFTS EAST  
AND SOUTH, WITH HEAVY SNOWS LIKELY IN UTAH AND COLORADO, AND LOWER ODDS FOR  
SNOWFALL IN NORTHERN ARIZONA AND NEW MEXICO.  
 
SOUTH OF THE TROUGH OVER THE WESTERN CONUS, HIGH PRESSURE IS PREDICTED.  
OFFSHORE WINDS ARE FORECAST OVER SOUTHERN CALIFORNIA, NOV 30, GIVING RISE TO  
CONDITIONS APPROACHING CRITICAL FIRE WEATHER CONDITIONS.  
 
AS THE WESTERN TROUGH MOVES EASTWARD, SOME RETURN FLOW IS LIKELY OVER THE  
SOUTHERN GREAT PLAINS. UNCERTAINTY ABOUT THE EXACT AMOUNT OF MOISTURE IS TOO  
HIGH TO DEPICT A THREAT, BUT THE MOST LIKELY AREAS ARE FROM TEXAS TO KANSAS,  
AND EASTWARD TO ARKANSAS, DURING MONDAY, DEC 4.  
 
AN ACTIVE PATTERN IS FORECAST FOR WESTERN AND SOUTHERN ALASKA. A 976 LOW IS  
FORECAST OVER THE EASTERN ALEUTIANS ON THURSDAY, NOV 30. HIGH WINDS (IN EXCESS  
OF 40 KNOTS) ARE LIKELY FOR MUCH OF THE ALEUTIANS AND SOUTHERN MAINLAND ALASKA.  
CORRESPONDINGLY, HIGH WAVES ARE LIKELY FOR THE SAME REGION, THOUGH THE THREAT  
OF SIGNIFICANT WAVE HEIGHTS ABOVE 20 FEET HAS DROPPED SINCE FRIDAY. AN  
LOW-PRESSURE IS FORECAST TO SPIN OFF OF THE PARENT LOW, AND MOVE ALONG THE  
SOUTHERN COAST OF ALASKA, BRINGING HEAVY PRECIPITATION (COASTAL RAIN, INLAND  
SNOW) TO SOUTHERN ALASKA AND THE ALASKA PANHANDLE. QPF TOTALS ARE LIKELY TO  
EXCEED 2 INCHES, SO HIGH SNOWFALL AMOUNTS ARE THE LIKELIEST THREAT.  
 
FOR TUESDAY DECEMBER 05 - MONDAY DECEMBER 11: THE PREVIOUSLY MENTIONED TROUGH  
PREDICTED ACROSS THE WEST IS LIKELY TO BRING COLDER AIR WITH IT. A SLIGHT RISK  
OF MINIMUM TEMPERATURES BEING BELOW THE 15TH PERCENTILE IS INDICATED FROM  
CALIFORNIA TO NORTHERN NEW MEXICO DURING DEC 5-6. TEMPERATURES ARE LIKELY TO  
FALL BELOW 40 DEG F, AND POTENTIALLY BRING FROSTS TO PORTIONS OF CALIFORNIA.  
 
ANOTHER SHOT OF COLDER AIR IS FORECAST TO DROP OVER THE SOUTHEAST LATER IN  
WEEK-2, IN A PREDICTED PATTERN CHANGE. MODEL OUTPUT FROM THE GEFS INDICATES THE  
POTENTIAL FOR A HEAVY RAIN EVENT IN THE TENNESSEE VALLEY EARLY IN WEEK-2. THE  
MODEL OUTPUT HAS SOME INDICATIONS OF BEING ASSOCIATED WITH CONVECTION,  
POTENTIALLY STRONG STORMS, AS PART OF THE PREDICTED PATTERN CHANGE.  
 
THE U.S. DROUGHT MONITOR, VALID ON NOV 21, INDICATES THAT SEVERE TO EXCEPTIONAL  
(D2-D4) DROUGHT COVERS 4.14 PERCENT OF THE CONTINENTAL U.S., WHICH IS A SLIGHT  
 
INCREASE FROM 3.52 PERCENT LAST WEEK. SEVERE DROUGHT HAS EXPANDED THIS MONTH  
ACROSS ARKANSAS AND MISSOURI.  
 
FORECASTER: MATTHEW ROSENCRANS  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page