892  
FXUS21 KWNC 121819  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT OCTOBER 12 2018  
 
SYNOPSIS: THE DAY 3-7 PERIOD IS FORECAST TO FEATURE UPPER LEVEL LOW PRESSURE  
ACROSS THE EASTERN US AND UPPER LEVEL HIGH PRESSURE EXPANDING INTO THE PLAINS.  
THE MOST PROMINENT SENSIBLE WEATHER DURING THE PERIOD IS FORECAST TO BE THE  
POTENTIAL FOR HEAVY RAIN ALONG THE TROUGH AXIS EARLY NEXT WEEK, WITH AN UPPER  
LEVEL DISTURBANCE OVER THE SOUTHWEST CONUS ENHANCING RAINFALL OVER TEXAS.  
MULTIPLE PIECES OF SHORTWAVE ENERGY ARE FORECAST TO ROTATE AROUND THE UPPER  
LEVEL LOW IN THE EAST, USHERING IN A COLDER AIR MASS, AND RESULTANT MUCH BELOW  
NORMAL TEMPERATURES FOR THE REGION. WEEK-2 IS FORECAST TO BE GENERALLY QUIET AS  
SURFACE HIGH PRESSURE BUILDS INTO THE MIDWEST. WHILE SOME MODERATION OF THE  
BELOW NORMAL TEMPERATURES IS FORECAST IN THE NORTHEAST, SEASONALLY CHILLY  
WEATHER IS STILL FAVORED AS UPPER LEVEL NORTHWEST FLOW IS FORECAST TO BRING  
COOLER TEMPERATURES DOWN FROM CANADA.  
 
HAZARDS  
 
HEAVY RAIN ACROSS PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY, THE  
CENTRAL AND SOUTHERN APPALACHIANS, THE TENNESSEE VALLEY, THE SOUTHERN PLAINS,  
AND THE OHIO VALLEY, MON-TUE, OCT 15-OCT 16.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, THE  
CENTRAL AND SOUTHERN APPALACHIANS, THE MIDDLE MISSISSIPPI VALLEY, AND THE  
MID-ATLANTIC.  
 
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN  
PLAINS, THE GREAT LAKES, THE UPPER AND MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN  
APPALACHIANS, THE SOUTHEAST, AND THE OHIO VALLEY.  
 
FLOODING LIKELY ACROSS PORTIONS OF THE NORTHERN PLAINS, THE SOUTHERN PLAINS,  
THE UPPER AND MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, AND THE SOUTHEAST.  
 
MUCH BELOW NORMAL TEMPERATURES ACROSS A LARGE AREA OF THE CENTRAL AND EASTERN  
CONUS, MON-FRI, OCT 15-OCT 19.  
 
ENHANCED WILDFIRE RISK ACROSS PORTIONS OF SOUTHERN CALIFORNIA, MON, OCT 15.  
 
HEAVY RAIN ACROSS PORTIONS OF THE ALASKA PANHANDLE AND SOUTHERN MAINLAND  
ALASKA, MON-TUE, OCT 15-OCT 16.  
 
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE GREAT LAKES,  
THE MID-ATLANTIC, THE NORTHEAST, THE CENTRAL APPALACHIANS, AND THE OHIO VALLEY,  
THU-FRI, OCT 25-OCT 26.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN  
PLAINS, THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL GREAT BASIN, AND THE  
SOUTHWEST, SAT-FRI, OCT 20-OCT 26.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE ALASKA PANHANDLE AND  
SOUTHERN MAINLAND ALASKA, SAT-MON, OCT 20-OCT 22.  
 
SEVERE DROUGHT ACROSS THE PLAINS, THE ROCKIES, THE NORTHEAST, THE NORTHERN AND  
CENTRAL GREAT BASIN, THE UPPER AND MIDDLE MISSISSIPPI VALLEY, CALIFORNIA, THE  
ALASKA PANHANDLE, THE PACIFIC NORTHWEST, AND THE SOUTHWEST.  
 
DETAILED SUMMARY  
 
FOR MONDAY OCTOBER 15 - FRIDAY OCTOBER 19: AN UPPER LEVEL LOW OVER THE  
SOUTHWEST COMBINED WITH FRONTOGENIC FORCING FROM A TROUGH DIGGING INTO THE  
PLAINS WILL FAVOR HEAVY RAIN DEVELOPMENT OVER TEXAS EXTENDING NORTHEAST THROUGH  
THE MISSISSIPPI AND TENNESSEE VALLEYS, AND POSSIBLY INTO THE OHIO VALLEY ON THE  
15TH. BY THE 16TH, THE TROUGH IS FORECAST TO MOVE FAR ENOUGH TO THE EAST  
FAVORING RAIN TO TAPER OFF IN PLACES DISPLACED FROM THE UPPER LEVEL LOW.  
HOWEVER, PORTIONS OF TEXAS ARE STILL FAVORED TO HAVE HEAVY RAIN ON THE 16TH.  
THE HIGHEST RAINFALL AMOUNTS ARE FAVORED OVER TEXAS WHERE TOTALS FOR THE  
15TH-16TH ARE IN THE 1-2 INCH RANGE BASED ON ENSEMBLE GUIDANCE FROM TODAY'S 00Z  
ECMWF AND 06Z GEFS. FOR AREAS FARTHER NORTHEAST, TOTALS ARE LESS WITH AMOUNTS  
GENERALLY IN THE 0.5-1.5 INCH RANGE, WITH THE GEFS BEING THE WETTEST, AND MOST  
RAIN PROJECTED TO OCCUR ON THE 15TH.  
 
THE POSITIVELY TILTED TROUGH FORECAST TO BE IN PLACE AT THE START OF THE PERIOD  
RESULTS IN MUCH BELOW NORMAL TEMPERATURES FAVORED FOR THE PLAINS AND INTO THE  
ROCKIES, WITH LOW TEMPERATURES 10-15 DEGREES F BELOW AVERAGE. TEMPERATURES IN  
THESE REGIONS ARE FORECAST TO MODERATE LATER IN THE PERIOD AS THE TROUGH SHIFTS  
EASTWARD, WITH THE CHANCES FOR MUCH BELOW NORMAL TEMPERATURES SPREADING INTO  
THE NORTHEAST. THE TEMPERATURE ANOMALIES ARE FORECAST TO NOT BE AS LOW BY THE  
TIME THE COLD AIR MASS REACHES THE NORTHEAST BY THE END OF NEXT WEEK, BUT THE  
THREAT FOR FIRST FROSTS AND FREEZES EXISTS, AND THEREFORE WILL CONTINUE TO  
HIGHLIGHT THE POTENTIAL IN TODAY'S OUTLOOK.  
 
SURFACE LOW PRESSURE IS FORECAST TO BE LOCATED OVER THE BERING SEA ON THE 15TH  
AND 16TH FAVORING A THREAT FOR HEAVY RAIN AND MOUNTAIN SNOW ACROSS THE SOUTHERN  
PART OF THE MAINLAND AND INTO THE PANHANDLE AS CYCLONIC FLOW AROUND THE LOW  
RESULTS IN A MOISTURE FLUX OUT OF THE GULF OF ALASKA. THE REMAINDER OF THE DAY  
3-7 PERIOD IS FORECAST TO CONTINUE TO HAVE HEAVY RAIN THREATS FOR THOSE SAME  
AREAS IN ASSOCIATION WITH AN ACTIVE STORM TRACK, BUT THERE IS LESS CONFIDENCE  
ON THE TIMING AND PLACEMENT OF THE HEAVIEST PRECIPITATION.  
 
GUSTY OFFSHORE WINDS ARE FORECAST TO DEVELOP EARLY NEXT WEEK OVER SOUTHERN  
CALIFORNIA. THOSE WINDS COMBINED WITH DRY SOILS FAVOR AN ENHANCED WILDFIRE  
THREAT FOR MONDAY. THESE CONDITIONS MAY LINGER THROUGH THE EARLY PART OF NEXT  
WEEK, BUT MONDAY IS HIGHLIGHTED DUE TO HAVING HIGHER CONFIDENCE.  
 
FOR SATURDAY OCTOBER 20 - FRIDAY OCTOBER 26: A RELATIVELY QUIET PATTERN IS  
FORECAST DURING THE WEEK-2 PERIOD AS SURFACE HIGH PRESSURE ESTABLISHES ITSELF  
OVER THE CENTRAL CONUS. SEASONABLY CHILLY WEATHER IS FAVORED FOR THE EASTERN  
CONUS. LATE IN WEEK-2 THERE IS SOME POTENTIAL FOR A MORE ROBUST SURGE OF COLD  
AIR PENETRATING SOUTHWARD. A SLIGHT RISK OF BELOW NORMAL TEMPERATURES IS  
INTRODUCED ON THE 25TH AND 26TH WHERE GEFS REFORECAST TOOLS BEGIN TO SHOW  
HIGHER PROBABILITIES FOR TEMPERATURES IN THE BOTTOM 15TH PERCENTILE.  
 
A WEAKNESS IN THE UPPER LEVEL FLOW ACROSS THE SOUTHWEST CONUS IS FORECAST TO  
PRODUCE ELEVATED PRECIPITATION CHANCES THROUGHOUT THE ENTIRE PERIOD. THE  
PROBABILISTIC PRECIPITATION REFORECAST TOOLS FROM THE ECMWF AND GEFS SUGGEST AT  
LEAST A 20% CHANCE OF PRECIPITATION VALUES GREATER THAN 85% OF CLIMATOLOGY  
THROUGHOUT THE PERIOD, WITH THE ECMWF REFORECAST TOOL FAVORING THE HIGHEST  
PROBABILITIES.  
 
THERE ARE SOME HINTS AT ELEVATED PRECIPITATION CHANCES OVER THE EASTERN CONUS  
AS ENERGY ROUNDING THE TROUGH IN THE EAST MAY TRIGGER CYCLOGENESIS OFF THE  
COAST AT SOME POINT DURING THE WEEK-2 PERIOD. HOWEVER, CONFIDENCE REMAINS TOO  
LOW AT THIS TIME TO INCLUDE IN TODAY'S OUTLOOK. NORTHWESTERLY FLOW MAY ALSO  
FAVOR LAKE EFFECT SNOW SHOWERS DURING THE PERIOD.  
 
A PERSISTENT TROUGH AXIS CENTERED OVER WESTERN ALASKA WILL CONTINUE TO FAVOR AN  
ACTIVE STORM TRACK WITH PERSISTENT SOUTHERLY FLOW FAVORED TO PRODUCE MULTIPLE  
ROUNDS OF PRECIPITATION FOR THE PANHANDLE AND SOUTHERN MAINLAND. THE ECMWF  
REFORECAST TOOL SHOWS HIGHER PRECIPITATION PROBABILITIES AT THE START OF THE  
WEEK-2 PERIOD THAN THE GEFS REFORECAST TOOL, WHICH NO LONGER EXCEEDS THE TOP  
15% PERCENTILE FOR PRECIPITATION. HOWEVER, BECAUSE OF THE SIMILAR PATTERN FROM  
THE DAY 3-7 PERIOD, A SLIGHT RISK OF HEAVY PRECIPITATION IS FAVORED FOR THE  
START OF WEEK-2 AS ANY CYCLONE THAT APPROACHES HAS THE POTENTIAL TO PRODUCE  
OVER 2 INCHES OF PRECIPITATION IN A 24 HOUR PERIOD. ADDITIONAL MODEL AGREEMENT  
IS DESIRED BEFORE EXTENDING THE HAZARD FURTHER.  
 
 
 
THE U.S. DROUGHT MONITOR, VALID OCTOBER 9TH, INDICATES A DECREASE IN SEVERE TO  
EXCEPTIONAL DROUGHT (D2 TO D4) COVERAGE FROM 17.03% TO 14.40% DURING THE PAST  
WEEK. SOME IMPROVEMENT IN DROUGHT CONDITIONS WAS NOTED OVER PARTS OF EASTERN  
KANSAS, MISSOURI, WEST TEXAS, AND UTAH. SOME DETERIORATION WAS NOTED IN PARTS  
OF THE NORTHERN PLAINS. NO CHANGES IN THE DROUGHT DEPICTION WERE RENDERED TO  
ALASKA OR PUERTO RICO. A SMALL AREA OF D0 WAS REMOVED OVER HAWAII.  
 
FORECASTER: THOMAS COLLOW  
 

 
 
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