820  
FXUS21 KWNC 232055  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT OCTOBER 23 2017  
 
SYNOPSIS: A LOW-PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE NORTHERN PLAINS  
AND MOVE TOWARD THE GREAT LAKES, WITH THE ASSOCIATED COLD FRONT PUSHING  
SOUTHWARD TO THE WESTERN GULF COAST. BEHIND THAT FRONT, HIGH PRESSURE IS  
FORECAST TO BUILD IN OVER THE GREAT PLAINS. DURING NEXT WEEKEND, A WAVE OF  
LOW-PRESSURE IS FORECAST TO DEVELOP ALONG THAT FRONT AND MOVE TOWARD THE  
NORTHEAST. A LOW-PRESSURE SYSTEM IS FORECAST TO IMPACT SOUTHERN ALASKA LATER  
NEXT WEEK, WITH A BRIEF LULL THEN ANOTHER ACTIVE PERIOD BEGINNING EARLY IN  
WEEK-2.  
 
HAZARDS  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE GREAT LAKES, THU, OCT 26.  
 
HEAVY RAIN ACROSS PORTIONS OF FLORIDA, SAT-SUN, OCT 28-OCT 29.  
 
HEAVY RAIN ACROSS PORTIONS OF THE MID-ATLANTIC AND NORTHEAST, SUN, OCT 29.  
 
HIGH WINDS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS, THE NORTHERN  
ROCKIES, AND THE UPPER AND MIDDLE MISSISSIPPI VALLEYS, THU-FRI, OCT 26-OCT 27.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE SOUTHERN AND CENTRAL  
PLAINS, THE MIDDLE AND LOWER MISSISSIPPI VALLEYS, AND THE TENNESSEE VALLEY,  
FRI-SUN, OCT 27-OCT 29.  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE ALASKA PANHANDLE AND SOUTHERN  
MAINLAND ALASKA, THU-FRI, OCT 26-OCT 27.  
 
HIGH WINDS ACROSS PORTIONS OF THE ALASKA PANHANDLE AND SOUTHERN MAINLAND  
ALASKA, THU-FRI, OCT 26-OCT 27.  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF THE ALASKA PANHANDLE AND SOUTHWESTERN  
MAINLAND ALASKA, MON-TUE, OCT 30-31.  
 
HIGH WINDS ACROSS PORTIONS OF SOUTHWESTERN MAINLAND ALASKA, MON-TUE, OCT 30-31.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL  
PLAINS, THE LOWER MISSISSIPPI VALLEY, THE CENTRAL APPALACHIANS, THE TENNESSEE  
VALLEY, THE GREAT LAKES, THE MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE  
SOUTHERN APPALACHIANS, THE UPPER MISSISSIPPI VALLEY, THE SOUTHEAST, THE  
SOUTHERN PLAINS, AND THE OHIO VALLEY, TUE-WED, OCT 31-NOV 1.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST, THE PACIFIC  
NORTHWEST, AND THE NORTHERN GREAT BASIN.  
 
FLOODING LIKELY ACROSS PORTIONS OF THE SOUTHERN PLAINS AND THE PACIFIC  
NORTHWEST.  
 
SEVERE DROUGHT ACROSS THE MIDDLE MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE  
NORTHERN ROCKIES, AND HAWAII.  
 
DETAILED SUMMARY  
 
FOR THURSDAY OCTOBER 26 - MONDAY OCTOBER 30: LOW-PRESSURE OVER THE NORTHERN  
GREAT PLAINS IS FORECAST TO MOVE TOWARD THE GREAT LAKES, WITH THE ASSOCIATED  
COLD FRONT MOVING SOUTHWARD OVER THE GREAT PLAINS. WITH THE LOW-PRESSURE  
SYSTEM, SOME LOCALLY HEAVY PRECIPITATION IS LIKELY OVER THE UPPER GREAT LAKES  
REGION, WITH SOME POTENTIAL FOR MIXED PRECIPITATION, THOUGH LITTLE ACCUMULATION  
IS PREDICTED. BEHIND THE FRONT, HIGH WINDS (40MPH SUSTAINED) ARE LIKELY OVER  
THE NORTHERN PLAINS, EXTENDING TOWARD THE UPPER GREAT LAKES. ALSO, MUCH BELOW  
NORMAL TEMPERATURES ARE LIKELY FROM THE SOUTHERN GREAT PLAINS TO THE TENNESSEE  
VALLEY, WITH THE AREA HIGHLIGHTED ON THE MAP INDICATING WHERE TEMPERATURES ARE  
LIKELY TO SUPPORT FROSTS AND FREEZES. EAST OF THE COLD FRONT, LOCALLY STRONG,  
BORDERLINE SEVERE STORMS ARE POSSIBLE ACROSS TEXAS, THE OZARK PLATEAU AND THE  
TENNESSEE VALLEY.  
 
A SECONDARY WAVE OF LOW-PRESSURE IS FORECAST TO DEVELOP ALONG THE FRONT, THEN  
MOVE NORTHWARD ALONG THE EAST COAST. HEAVY RAINS ARE LIKELY TO OVERSPREAD THE  
NORTHEAST ON OCT 29, WITH TOTALS APPROACHING 2 INCHES IN 24 HOURS, AND SOME  
POTENTIAL FOR HEAVY FROZEN PRECIPITATION AT ELEVATION.  
 
AN INTENSE LOW-PRESSURE SYSTEM IS FORECAST NEAR THE EASTERN ALEUTIANS DURING  
THE LATTER PORTION OF NEXT WEEK, BEFORE IT MOVES TOWARD SOUTHERN COASTAL ALASKA  
AND THE PANHANDLE. HEAVY PRECIPITATION (WIDESPREAD 2 INCHES, WITH LOCALLY UP TO  
4 INCHES LIQUID EQUIVALENT) AND HIGH WINDS (IN EXCESS OF 45 MPH) ARE LIKELY TO  
SPREAD FROM WEST TO EAST, LEADING INTO THE WEEKEND. EARLY NEXT WEEK, ANOTHER  
LOW-PRESSURE SYSTEM IS FORECAST TO MOVE, FROM THE SOUTH, TOWARD THE CENTRAL  
ALEUTIANS. THIS SYSTEM WOULD FAVOR HIGH WINDS AND HEAVY PRECIPITATION FOR THE  
ALEUTIANS AND THE ALASKA PENINSULA, BEFORE THE SYSTEM MOVES EAST AND BRINGS  
THOSE HAZARDS TO SOUTH CENTRAL ALASKA, DURING THE MIDDLE OF NEXT WEEK.  
 
THE NATIONAL HURRICANE CENTER INDICATES A 40 PERCENT CHANCE OF TROPICAL CYCLONE  
FORMATION OVER THE WESTERN CARIBBEAN. THIS AREA WILL BE MONITORED FOR  
DEVELOPMENT AND ANY POTENTIALLY PREDICTABLE HAZARDS.  
 
FLOODING IS EXPECTED TO CONTINUE IN THE PACIFIC NORTHWEST AND IN FLORIDA.  
CONDITIONS IN THE PACIFIC NORTHWEST ARE LIKELY TO RETURN TO NORMAL WITHIN THE  
NEXT 3 DAYS.  
 
FOR TUESDAY OCTOBER 31 - MONDAY NOVEMBER 06: WHILE THE REFORECAST CALIBRATED  
GEFS OUTLOOK IMPLIES A MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES, THE  
SAME CALIBRATION APPLIED TO THE ECMWF ENSEMBLE RESULTS IN A MUCH WARMER  
OUTLOOK, SO ONLY A SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES IS INDICATED  
FOR DAYS 8-9 (OCT 31 - NOV 1).  
 
THE U.S. DROUGHT MONITOR, VALID ON OCTOBER 10, INDICATES THAT SEVERE TO  
EXCEPTIONAL (D2-D4) DROUGHT COVERS 2.98 PERCENT OF THE CONTINENTAL U.S., DOWN  
FROM 4.03 PERCENT OF THE CONUS. THE LARGEST CHANGES WERE OVER THE NORTHERN  
PLAINS AND MIDWEST.  
 
FORECASTER: MATTHEW ROSENCRANS  
 

 
 
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