Climate Prediction Center

US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT SEPTEMBER 15 2008

SYNOPSIS: AFTER A VERY ACTIVE PATTERN ACROSS THE US DURING THE PAST FEW WEEKS, THE ASSESSMENT PERIOD WILL FEATURE RELATIVELY TRANQUIL CONDITIONS ACROSS MUCH OF THE COUNTRY AS HIGH PRESSURE WILL DOMINATE MUCH OF THE PERIOD. HEAVY RAINFALL ASSOCIATED WITH RECENT TROPICAL CYCLONE ACTIVITY WILL CONTINUE THE THREAT FOR FLOODING STRETCHING FROM THE SOUTH-CENTRAL PLAINS ACROSS THE MIDDLE MISSISSIPPI VALLEY TO THE SOUTHWESTERN GREAT LAKES. A RIDGE OF HIGH PRESSURE ACROSS THE NORTH-CENTRAL US WILL RESULT IN ABOVE-AVERAGE TEMPERATURES ACROSS THE NORTHERN PLAINS, UPPER-MISSISSIPPI VALLEY AND WESTERN GREAT LAKES.

HAZARDS

ONGOING RIVER FLOODING FROM THE SOUTH-CENTRAL PLAINS TO THE SOUTHWESTERN GREAT LAKES THROUGHOUT THE PERIOD.
RIVER FLOODING FOR SOUTHWESTERN TEXAS SEP 18-19.
LINGERING FLOODING FOR EAST-CENTRAL FLORIDA SEP 18-20.
RIVER FLOODING FOR SOUTHERN ARKANSAS SEP 18-19.
RIVER FLOODING FOR SOUTHWESTERN LOUISIANA SEP 18-20.
MUCH ABOVE AVERAGE TEMPERATURES FOR THE NORTHERN PLAINS AND UPPER-MISSISSIPPI VALLEY SEP 18-21
SEVERE DROUGHT WILL CONTINUE FOR PARTS OF CALIFORNIA, OREGON, NEVADA, WYOMING, NORTH DAKOTA, MONTANA, TEXAS, OKLAHOMA, KANSAS, COLORADO, SOUTH CAROLINA, GEORGIA, TENNESSEE, AND NORTH CAROLINA

DETAILED SUMMARY

FOR THURSDAY SEPTEMBER 18 - SATURDAY SEPTEMBER 20: RECENT VERY HEAVY AND EXTENSIVE RAINFALL ASSOCIATED WITH TROPICAL SYSTEMS IKE AND LOWELL AND A FRONTAL SYSTEM PRODUCED LARGE RAINFALL TOTALS ACROSS PORTIONS OF THE CENTRAL US. THE PRECIPITATION TOTALS DURING THE PAST 7 DAYS RANGED FROM 3-10 INCHES WITH LOCALLY HEAVIER AMOUNTS OVER A LARGE AREA STRETCHING FROM KANSAS TO SOUTHERN MICHIGAN. EXTENSIVE FLOODING IS EXPECTED TO CONTINUE WELL INTO THE ASSESSMENT PERIOD FROM THE SOUTH-CENTRAL PLAINS TO THE SOUTHERN GREAT LAKES. MOREOVER, LINGERING FLOODING IS EXPECTED TO CONTINUE FOR SECTIONS OF EAST-CENTRAL FLORIDA, SOUTHERN ARKANSAS, SOUTHWEST LOUISIANA, AND SOUTHWEST TEXAS DUE TO PREVIOUS TROPICAL SYSTEMS. HIGH PRESSURE WILL PREVAIL OVER MUCH OF THE COUNTRY DURING THE PERIOD SO FURTHER SUBSTANTIAL RAINFALL IS NOT EXPECTED DURING THE PERIOD AT THIS TIME SO FLOODING RELIEF EFFORTS WILL NOT BE INHIBITED SIGNIFICANTLY. AN UPPER-LEVEL RIDGE WILL RESULT IN SUFFICIENTLY HIGH POSITIVE 500-HPA HEIGHT ANOMALIES ACROSS THE NORTHERN PLAINS EARLY DURING THE PERIOD TO RESULT IN MUCH ABOVE-NORMAL TEMPERATURES IN THIS REGION. TEMPERATURES IN THIS REGION WILL REACH 12-16 DEGREES ABOVE AVERAGE IN MANY LOCATIONS ESPECIALLY ACROSS THE NORTHERN PLAINS. THE AREA IS LIKELY TO SLOWLY SHIFT EASTWARD DURING THE PERIOD BUT TEMPERATURES WILL LIKELY ONLY RANGE 8-12 DEGREES ABOVE AVERAGE. AN AREA OF DISTURBED WEATHER WILL PERSIST OFF THE SOUTHEAST COAST DURING THE FORECAST PERIOD AND INTERESTS ALONG THE SOUTHEAST COAST FROM GEORGIA TO NORTH CAROLINA SHOULD MONITOR FOR STRONG WAVE ACTION AND POTENTIAL BEACH EROSION AND COASTAL FLOODING. SEVERE DROUGHT WILL REMAIN ACROSS PARTS OF CALIFORNIA, THE INTER-MOUNTAIN WEST, NORTHERN PLAINS, SOUTH CENTRAL PLAINS AND SOUTHEAST. MOST AREAS WILL NOT SEE ANY RELIEF DURING THE PERIOD. DUE TO RECENT RAINFALL FROM TROPICAL SYSTEMS THE SEVERE DROUGHT AREA IN SOUTHERN TEXAS WILL SEE SOME RELIEF. IN PART ASSOCIATED WITH THE CURRENT PHASE OF THE MADDEN-JULIAN OSCILLATION (MJO), THE DEEP TROPICAL ATLANTIC SHOULD CONTINUE TO SEE GENERALLY SUPPRESSED TROPICAL CYCLONE ACTIVITY.

FOR SUNDAY SEPTEMBER 21 - THURSDAY SEPTEMBER 25: THIS FORECAST PERIOD WILL SEE THE CONTINUATION OF GENERAL HIGH PRESSURE ACROSS MUCH OF THE COUNTRY. FLOODING WILL REMAIN A CONCERN DURING THE PERIOD ACROSS A LARGE REGION OF THE CENTRAL US ESPECIALLY THE UPPER-MISSISSIPPI VALLEY. CONTINUED GENERALLY QUIET CONDITIONS WILL LIMIT ANY DROUGHT RELIEF FOR CURRENT SEVERE DROUGHT AREAS. DURING THIS FORECAST PERIOD, THE ENHANCED PHASE OF THE MJO IS EXPECTED TO CONTINUE SHIFTING EASTWARD AND THE LIKELIHOOD OF TROPICAL DEVELOPMENT ACROSS THE EASTERN PACIFIC AND FAR WESTERN GULF OF MEXICO AND CARIBBEAN INCREASES.

FOR FRIDAY SEPTEMBER 26 - MONDAY SEPTEMBER 29: THE ENHANCED PHASE OF THE MJO IS EXPECTED TO CONTINUE SHIFTING EASTWARD DURING THIS FORECAST PERIOD AND THE LIKELIHOOD OF TROPICAL DEVELOPMENT ACROSS THE DEEP TROPICAL ATLANTIC INCREASES. THE THREAT FOR DEVELOPMENT IS EXPECTED TO REMAIN ELEVATED ACROSS THE FAR EASTERN PACIFIC, GULF OF MEXICO AND CARIBBEAN DURING THE PERIOD. THE LACK OF PREDICTABILITY AT THIS TIME RANGE PRECLUDES THE FORECAST OF SPECIFIC HAZARDS ACROSS THE CONUS.

FORECASTER: JON GOTTSCHALCK

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