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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