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FXUS21 KWNC 071939 PMDTHR US HAZARDS ASSESSMENT NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT SEPTEMBER 07 2010 SYNOPSIS: AT THE BEGINNING OF THE PERIOD, THE REMNANT LOW ASSOCIATED WITH TROPICAL STORM HERMINE IS FORECAST TO TRACK ACROSS PORTIONS OF THE MIDWEST AND OHIO VALLEY. A LOW PRESSURE SYSTEM AND TRAILING COLD FRONT ARE EXPECTED TO SLOWLY PROGRESS ACROSS THE PLAINS AND MISSISSIPPI VALLEY. BROAD HIGH PRESSURE IS ANTICIPATED TO FOLLOW IN THE WAKE OF THIS SYSTEM ACROSS THE CENTRAL STATES. TOWARDS THE MIDDLE OF THE ASSESSMENT PERIOD, THIS COLD FRONT IS FORECAST TO MOVE OFF THE ATLANTIC COAST AND OUT OVER THE WESTERN ATLANTIC, FOLLOWED BY ANOTHER SURGE OF COOLER CANADIAN AIR MOVING SOUTHEASTWARD ACROSS THE GREAT LAKES REGION AND MIDWEST. A SERIES OF LOW PRESSURE SYSTEMS ARE FORECAST TO AFFECT THE ALEUTIANS AND WESTERN ALASKA DURING THIS PERIOD. HAZARDS HEAVY RAIN AND LOCALIZED FLOODING FOR EASTERN PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY AND ADJACENT PORTIONS OF THE LOWER OHIO VALLEY, SEPTEMBER 10. MUCH BELOW NORMAL TEMPERATURES FOR CENTRAL PORTIONS OF BOTH THE GREAT BASIN AND ROCKIES, SEPTEMBER 10. SEVERE DROUGHT FOR SOUTHERN OREGON, NORTHERN ARIZONA, MUCH OF HAWAII, PARTS OF THE UPPER AND LOWER MISSISSIPPI VALLEY, AND THE MID-ATLANTIC REGION. SOME RELIEF IS EXPECTED IN THE UPPER MISSISSIPPI VALLEY. DETAILED SUMMARY FOR FRIDAY SEPTEMBER 10 - SUNDAY SEPTEMBER 12: BY THE START OF THIS PERIOD, THE REMNANTS OF TROPICAL STORM HERMINE ARE EXPECTED TO MOVE ACROSS THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. ALONG THE PATH OF THIS REMNANT TROPICAL LOW, ABUNDANT MOISTURE IS EXPECTED TO HEIGHTEN THE RISK OF HEAVY RAIN (3 TO 4 INCHES) AND FLASH FLOODING. AT THE SAME TIME, AN OCCLUDED FRONTAL SYSTEM IS FORECAST TO MOVE INTO THE MISSISSIPPI VALLEY, WITH THE PRIMARY AREA OF LOW PRESSURE AND THE MAIN DYNAMICS ASSOCIATED WITH THE 500-HPA TROUGH HEADING INTO SOUTHERN CANADA. ACROSS NORTH DAKOTA AND NORTHWEST MINNESOTA, AN INCH OF RAIN IS ANTICIPATED. WET ANTECEDENT CONDITIONS IN THESE AREAS ELEVATE THE RISK FOR FLOODING WITH ANY HEAVY RAINFALL THAT OCCURS. FARTHER SOUTH, OVER EASTERN NEBRASKA AND WESTERN IOWA, A TRIPLE-POINT LOW PRESSURE CENTER ASSOCIATED WITH THIS OCCLUDED SYSTEM MAY HELP TO ENHANCE THE RISK OF STRONG TO SEVERE THUNDERSTORMS, THOUGH THERE IS NOT ENOUGH CONFIDENCE AT THIS TIME TO WARRANT A DEPICTION ON THE MAP. IN THE WAKE OF THIS OCCLUDED FRONTAL SYSTEM, MUCH BELOW-NORMAL TEMPERATURES ARE PREDICTED OVER THE WESTERN CONUS, WITH THE LARGEST NEGATIVE TEMPERATURE DEPARTURES (-12 TO -16 DEGREES F) IN THE CENTRAL GREAT BASIN. ON FRIDAY MORNING, SEPTEMBER 10TH, WIDESPREAD FREEZING TEMPERATURES CAN BE EXPECTED IN NORTHERN NEVADA. ACCORDING TO THE NATIONAL INTERAGENCY FIRE CENTER, 2.6 MILLION ACRES HAVE BURNED SINCE JANUARY 1, WELL BELOW THE 10-YEAR AVERAGE OF 5.8 MILLION ACRES. LATER IN THE WEEK, COOLER TEMPERATURES AND LIGHTER WINDS ARE EXPECTED TO LOWER THE WILDFIRE DANGER. FOR MONDAY SEPTEMBER 13 - FRIDAY SEPTEMBER 17: THE 500-HPA FLOW PATTERN DURING THIS FORECAST PERIOD IS EXPECTED TO TRANSITION FROM RELATIVELY FAST ZONAL FLOW TO A LOW-AMPLITUDE PATTERN FEATURING TROUGHS NEAR BOTH COASTS, AND A WEAK RIDGE OVER THE SOUTH-CENTRAL CONUS. MOST OF ALASKA IS PREDICTED TO BE DOMINATED BY A RIDGE. ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES ARE FORECAST ACROSS THE SOUTH-CENTRAL U.S. AND ALASKA, WHILE ENHANCED ODDS FOR BELOW NORMAL TEMPERATURES ARE FORECAST IN THE WEST. ENHANCED ODDS FOR ABOVE MEDIAN PRECIPITATION ARE EXPECTED IN THE NORTHWEST, THE UPPER MISSISSIPPI VALLEY, AND THE WESTERN COAST OF ALASKA. FOR SATURDAY SEPTEMBER 18 - TUESDAY SEPTEMBER 21: NO SPECIFIC HAZARDS CAN BE DEFINED AT THIS TIME RANGE, EXCEPT THE AREAS OF PERSISTENT, LONG-TERM DROUGHT. SEVERE DROUGHT CONTINUES IN PARTS OF THE MID-ATLANTIC, UPPER MISSISSIPPI VALLEY, LOUISIANA, NORTHERN ARIZONA AND SOUTHERN OREGON. SOME DROUGHT RELIEF IS ANTICIPATED IN THE UPPER MISSISSIPPI VALLEY. WITHOUT RAINFALL FROM A TROPICAL SYSTEM, SEVERE DROUGHT IS EXPECTED TO PERSIST IN NORTHERN LOUISIANA AND THE MID-ATLANTIC. RAINFALL ASSOCIATED WITH THE NORTH AMERICAN MONSOON TYPICALLY DECREASES SIGNIFICANTLY BY MID-SEPTEMBER. EASTERLY WAVES EMERGING FROM WEST AFRICA INTO AN AREA OF WEAK VERTICAL WIND SHEAR AND ABOVE NORMAL SSTS INCREASE THE CHANCE FOR TROPICAL CYCLONE DEVELOPMENT IN THE TROPICAL ATLANTIC. FORECASTER: ANTHONY ARTUSA $$
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FXUS21 KWNC 071939
PMDTHR
US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT SEPTEMBER 07 2010

SYNOPSIS: AT THE BEGINNING OF THE PERIOD, THE REMNANT LOW ASSOCIATED WITH 
TROPICAL STORM HERMINE IS FORECAST TO TRACK ACROSS PORTIONS OF THE MIDWEST AND 
OHIO VALLEY. A LOW PRESSURE SYSTEM AND TRAILING COLD FRONT ARE EXPECTED TO 
SLOWLY PROGRESS ACROSS THE PLAINS AND MISSISSIPPI VALLEY. BROAD HIGH PRESSURE 
IS ANTICIPATED TO FOLLOW IN THE WAKE OF THIS SYSTEM ACROSS THE CENTRAL STATES. 
TOWARDS THE MIDDLE OF THE ASSESSMENT PERIOD, THIS COLD FRONT IS FORECAST TO 
MOVE OFF THE ATLANTIC COAST AND OUT OVER THE WESTERN ATLANTIC, FOLLOWED BY 
ANOTHER SURGE OF COOLER CANADIAN AIR MOVING SOUTHEASTWARD ACROSS THE GREAT 
LAKES REGION AND MIDWEST. A SERIES OF LOW PRESSURE SYSTEMS ARE FORECAST TO 
AFFECT THE ALEUTIANS AND WESTERN ALASKA DURING THIS PERIOD.

HAZARDS

HEAVY RAIN AND LOCALIZED FLOODING FOR EASTERN PORTIONS OF THE MIDDLE 
MISSISSIPPI VALLEY AND ADJACENT PORTIONS OF THE LOWER OHIO VALLEY, SEPTEMBER 10.

MUCH BELOW NORMAL TEMPERATURES FOR CENTRAL PORTIONS OF BOTH THE GREAT BASIN AND 
ROCKIES, SEPTEMBER 10.

SEVERE DROUGHT FOR SOUTHERN OREGON, NORTHERN ARIZONA, MUCH OF HAWAII, PARTS OF 
THE UPPER AND LOWER MISSISSIPPI VALLEY, AND THE MID-ATLANTIC REGION. SOME 
RELIEF IS EXPECTED IN THE UPPER MISSISSIPPI VALLEY.

DETAILED SUMMARY

FOR FRIDAY SEPTEMBER 10 - SUNDAY SEPTEMBER 12: BY THE START OF THIS PERIOD, THE 
REMNANTS OF TROPICAL STORM HERMINE ARE EXPECTED TO MOVE ACROSS THE MIDDLE 
MISSISSIPPI AND OHIO VALLEYS. ALONG THE PATH OF THIS REMNANT TROPICAL LOW, 
ABUNDANT MOISTURE IS EXPECTED TO HEIGHTEN THE RISK OF HEAVY RAIN (3 TO 4 
INCHES) AND FLASH FLOODING. AT THE SAME TIME, AN OCCLUDED FRONTAL SYSTEM IS 
FORECAST TO MOVE INTO THE MISSISSIPPI VALLEY, WITH THE PRIMARY AREA OF LOW 
PRESSURE AND THE MAIN DYNAMICS ASSOCIATED WITH THE 500-HPA TROUGH HEADING INTO 
SOUTHERN CANADA. ACROSS NORTH DAKOTA AND NORTHWEST MINNESOTA, AN INCH OF RAIN 
IS ANTICIPATED. WET ANTECEDENT CONDITIONS IN THESE AREAS ELEVATE THE RISK FOR 
FLOODING WITH ANY HEAVY RAINFALL THAT OCCURS. FARTHER SOUTH, OVER EASTERN 
NEBRASKA AND WESTERN IOWA, A TRIPLE-POINT LOW PRESSURE CENTER ASSOCIATED WITH 
THIS OCCLUDED SYSTEM MAY HELP TO ENHANCE THE RISK OF STRONG TO SEVERE 
THUNDERSTORMS, THOUGH THERE IS NOT ENOUGH CONFIDENCE AT THIS TIME TO WARRANT A 
DEPICTION ON THE MAP.



IN THE WAKE OF THIS OCCLUDED FRONTAL SYSTEM, MUCH BELOW-NORMAL TEMPERATURES ARE 
PREDICTED OVER THE WESTERN CONUS, WITH THE LARGEST NEGATIVE TEMPERATURE 
DEPARTURES (-12 TO -16 DEGREES F) IN THE CENTRAL GREAT BASIN. ON FRIDAY 
MORNING, SEPTEMBER 10TH, WIDESPREAD FREEZING TEMPERATURES CAN BE EXPECTED IN 
NORTHERN NEVADA.



ACCORDING TO THE NATIONAL INTERAGENCY FIRE CENTER, 2.6 MILLION ACRES HAVE 
BURNED SINCE JANUARY 1, WELL BELOW THE 10-YEAR AVERAGE OF 5.8 MILLION ACRES. 
LATER IN THE WEEK, COOLER TEMPERATURES AND LIGHTER WINDS ARE EXPECTED TO LOWER 
THE WILDFIRE DANGER.

FOR MONDAY SEPTEMBER 13 - FRIDAY SEPTEMBER 17: THE 500-HPA FLOW PATTERN DURING 
THIS FORECAST PERIOD IS EXPECTED TO TRANSITION FROM RELATIVELY FAST ZONAL FLOW 
TO A LOW-AMPLITUDE PATTERN FEATURING TROUGHS NEAR BOTH COASTS, AND A WEAK RIDGE 
OVER THE SOUTH-CENTRAL CONUS. MOST OF ALASKA IS PREDICTED TO BE DOMINATED BY A 
RIDGE. ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES ARE FORECAST ACROSS THE 
SOUTH-CENTRAL U.S. AND ALASKA, WHILE ENHANCED ODDS FOR BELOW NORMAL 
TEMPERATURES ARE FORECAST IN THE WEST. ENHANCED ODDS FOR ABOVE MEDIAN 
PRECIPITATION ARE EXPECTED IN THE NORTHWEST, THE UPPER MISSISSIPPI VALLEY, AND 
THE WESTERN COAST OF ALASKA.

FOR SATURDAY SEPTEMBER 18 - TUESDAY SEPTEMBER 21: NO SPECIFIC HAZARDS CAN BE 
DEFINED AT THIS TIME RANGE, EXCEPT THE AREAS OF PERSISTENT, LONG-TERM DROUGHT. 
SEVERE DROUGHT CONTINUES IN PARTS OF THE MID-ATLANTIC, UPPER MISSISSIPPI 
VALLEY, LOUISIANA, NORTHERN ARIZONA AND SOUTHERN OREGON. SOME DROUGHT RELIEF IS 
ANTICIPATED IN THE UPPER MISSISSIPPI VALLEY. WITHOUT RAINFALL FROM A TROPICAL 
SYSTEM, SEVERE DROUGHT IS EXPECTED TO PERSIST IN NORTHERN LOUISIANA AND THE 
MID-ATLANTIC. RAINFALL ASSOCIATED WITH THE NORTH AMERICAN MONSOON TYPICALLY 
DECREASES SIGNIFICANTLY BY MID-SEPTEMBER. EASTERLY WAVES EMERGING FROM WEST 
AFRICA INTO AN AREA OF WEAK VERTICAL WIND SHEAR AND ABOVE NORMAL SSTS INCREASE 
THE CHANCE FOR TROPICAL CYCLONE DEVELOPMENT IN THE TROPICAL ATLANTIC.

FORECASTER: ANTHONY ARTUSA 

$$