Climate Prediction Center

US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST NOVEMBER 06 2009

SYNOPSIS: THE ASSESSMENT PERIOD IS EXPECTED TO FEATURE ACTIVE WEATHER ACROSS THE GULF COAST, SOUTHEAST, PACIFIC NORTHWEST, AND PORTIONS OF ALASKA. A WEAK LOW-PRESSURE SYSTEM IS EXPECTED TO TRAVERSE THE NORTHERN TIER OF THE COUNTRY WITH AN ASSOCIATED COLD FRONT MOVING FROM THE GREAT PLAINS TO THE EASTERN SEABOARD BY THE MIDDLE OF NEXT WEEK. LATE SEASON INFLUENCES OF A TROPICAL NATURE COULD AFFECT THE SOUTHEAST. ANOTHER, MORE POTENT LOW-PRESSURE SYSTEM, IS EXPECTED TO MOVE ONSHORE ACROSS THE PACIFIC NORTHWEST. DURING THE MIDDLE PORTIONS OF THE ASSESSMENT PERIOD, THE PRIMARY AREA OF UNSETTLED WEATHER IS EXPECTED TO SHIFT TO THE CENTRAL PORTIONS OF THE COUNTRY, AS A LOW-PRESSURE SYSTEM DEVELOPS EAST OF THE CENTRAL ROCKIES AND MOVES NORTHEAST ACROSS THE GREAT PLAINS. THE EASTERN THIRD OF THE COUNTRY SHOULD COME UNDER THE CALMING INFLUENCE OF HIGH PRESSURE. THE FOCUS OF ACTIVE WEATHER ACROSS ALASKA IS EXPECTED TO SHIFT FROM SOUTHEAST ALAKSA TO WESTERN ALASKA AND THE ALEUTIANS.

HAZARDS

ONGOING FLOODING FOR PARTS OF THE CENTRAL AND SOUTHERN MISSISSIPPI VALLEY, AS WELL AS FOR EASTERN PORTIONS OF TEXAS.
HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST, NOV 9.
PERIODS OF HEAVY PRECIPITATION FOR SOUTHEAST ALASKA, NOV 9-10, 12-13.
HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHEAST, NOV 9-12.
HEAVY PRECIPITATION FOR WESTERN ALASKA, NOV 11-12.
SEVERE DROUGHT CONTINUES IN PARTS OF WISCONSIN, TEXAS, ARIZONA, NEW MEXICO, CALIFORNIA, NEVADA, AND WASHINGTON. SOME RELIEF IS EXPECTED ACROSS WISCONSIN, WASHINGTON, NORTHERN CALIFORNIA, AND SOUTH CAROLINA.

DETAILED SUMMARY

FOR MONDAY NOVEMBER 09 - WEDNESDAY NOVEMBER 11: A RIDGE OF HIGH PRESSURE IS FORECAST ALONG THE EAST COAST. ON THE SOUTHERN FLANK OF THIS RIDGE, STRONG EASTERLIES ACROSS MOST OF THE EAST COAST OF FLORIDA AND PORTIONS OF GEORGIA ARE EXPECTED TO PERSIST THROUGH MONDAY, NOVEMBER 9. WINDS RANGING FROM 20-30 MPH ARE POSSIBLE, WITH THE HIGHEST WINDS FURTHER SOUTH. THIS TYPE OF WEATHER PATTERN IS ALSO ASSOCIATED WITH DANGEROUS RIP CURRENTS, MINOR COASTAL EROSION, AND RED FLAG WARNINGS ACROSS FLORIDA. CONCERNED PARTIES SHOULD CONTACT THE LOCAL WEATHER FORECAST OFFICE FOR MORE INFORMATION.

A SURGE OF TROPICAL MOISTURE, INTERACTING WITH THE COLD FRONT THAT IS EXPECTED TO MOVE INTO THE SOUTHEAST, SHOULD PROVIDE SIGNIFICANT RAINFALL TO PORTIONS OF THE SOUTHEAST. ADDITIONALLY, MOISTURE ASSOCIATED WITH TROPICAL STORM IDA SHOULD PROVIDE A SECOND MOISTURE SURGE. CONSULT FORECAST PRODUCTS FROM THE NATIONAL HURRICANE CENTER (WWW.NHC.NOAA.GOV) FOR MORE INFORMATION ON THE TRACK AND INTENSITY OF TROPICAL STORM IDA.

HIGH PRESSURE TO THE NORTH SHOULD LIMIT THE NORTHWARD PROGRESSION OF THE MOISTURE ACROSS THE SOUTHEAST, POTENTIALLY CAUSING FLOODING RAINS ACROSS ALABAMA, GEORGIA, AND FLORIDA. CONTACT YOUR LOCAL WEATHER FORECAST OFFICE AND HEED WARNINGS FROM LOCAL AUTHORITIES.

FURTHER NORTH, ON THE EASTERN FLANK OF THE HIGH PRESSURE THAT IS FORECAST TO BUILD IN BEHIND THE COLD FRONT, WINDY CONDITIONS ARE LIKELY ACROSS THE NORTHEAST WEDNESDAY NOVEMBER 11.

ACROSS THE PACIFIC NORTHWEST, A POTENT LOW-PRESSURE SYSTEM IS FORECAST TO MOVE ONSHORE IN BRITISH COLUMBIA DURING THE DAY ON NOVEMBER 9. RAINFALL AMOUNTS COULD EXCEED 3 INCHES ACROSS SOME PARTS OF WASHINGTON AND OREGON, BEFORE THE RAINS ABATE DURING THE DAY ON NOVEMBER 10.

MULTIPLE STORM SYSTEMS ARE FORECAST TO IMPACT ALASKA WITH A STRONG COLD FRONT FORECAST TO MOVE ACROSS WESTERN ALASKA AND THE ALEUTIANS NOVEMBER 10. BEHIND THAT COLD FRONT, WIND SPEEDS BETWEEN 30 AND 40 MPH ARE POSSIBLE IN ISOLATED PLACES, WITH MOST WIND SPEEDS NOT MEETING HAZARD CRITERIA. A SECOND LOW-PRESSURE SYSTEM IS FORECAST TO DEVELOP ON THE WESTERN END OF THAT COLD FRONT, BRINGING SIGNIFICANT PRECIPITATION AND BLOWING SNOW ACROSS WESTERN ALASKA THROUGH NOVEMBER 12.

FOR THURSDAY NOVEMBER 12 - MONDAY NOVEMBER 16: A SHORTWAVE IS FORECAST TO MOVE SOUTHWARD ALONG THE PACIFIC COAST DURING THE MIDDLE OF NEXT WEEK. UNCERTAINTY ABOUT THE STRENGTH OF SURFACE REFLECTION OF THAT SHORTWAVE IS HIGH, AS THE 12Z ECMWF SOLUTION DEPICTS A 1006MB LOW JUST WEST OF PUGET SOUND WHILE THE 12Z GFS SOLUTION DEPICTS RIDGING, AND A MUCH WEAKER SHORTWAVE. PRECIPITATION AMOUNTS INDICATED IN THE MODEL SOLUTIONS VARY GREATLY AS A RESULT OF THE VARIANCE IN STRUCTURE, THEREFORE NO HAZARD IS DEPICTED DUE TO HIGH UNCERTAINTY IN THE TIMING OF THE FEATURES.

BOTH MODELS DO COME INTO BETTER AGREEMENT ON THE DEVELOPMENT OF A LOW-PRESSURE SYSTEM ACROSS THE CENTRAL ROCKIES DURING THE MIDDLE OF NEXT WEEK. BOTH MODELS INDICATE THAT THE LOW-PRESSURE SYSTEM SHOULD MOVE INTO THE CENTRAL GREAT PLAINS, BUT VARY WIDELY ON THE AMOUNT OF PRECIPITATION. GIVEN THE LOCATION OF THE LOW-PRESSURE SYSTEM AND WIND DIRECTION, SIGNIFICANT OROGRAPHIC ENHANCEMENT OF PRECIPITATION IS LIKELY ACROSS WYOMING , IDAHO AND NORTHERN COLORADO, BUT A BROADER HAZARD CANNOT BE DEPICTED DUE TO UNCERTAINTY IN THE FORECAST.

THE SECOND LOW-PRESSURE SYSTEM MOVING ACROSS ALASKA IS EXPECTED TO MOVE INTO THE GULF OF ALASKA LATE NEXT WEEK, AND SHOULD BRING ANOTHER ROUND OF HEAVY PRECIPITATION TO SOUTHEAST ALASKA AND THE ALASKAN PANHANDLE.

FOR TUESDAY NOVEMBER 17 - FRIDAY NOVEMBER 20: A STRONG TROUGH IS FORECAST TO EXTEND FROM CENTRAL ALASKA TO THE EASTERN PACIFIC WITH RIDGING PRESENT FROM THE FOUR CORNERS REGION TO THE GREAT LAKES. THIS PATTERN IS EXPECTED TO SUPPORT WET CONDITIONS ACROSS SOUTHEASTERN ALASKA, THE WEST COAST AND FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC. WARMER THAN AVERAGE CONDITIONS ARE EXPECTED ACROSS THE NORTHERN TIER OF THE COUNTRY.

SEVERE DROUGHT IS EXPECTED TO PERSIST ACROSS CALIFORNIA, NEVADA, ARIZONA, AND NEW MEXICO. SOME DROUGHT RELIEF IS EXPECTED ACROSS WISCONSIN, TEXAS, NORTHERN CALIFORNIA, AND SOUTH CAROLINA.

FORECASTER: MATT ROSENCRANS

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