| Link to detailed discussion with graphics maps: http://www.cpc.noaa.gov/products/predictions/threats/threats.php Valid Monday, September 27, 2010 - Friday, October 08, 2010 Summary of Forecasts & Hazards US HAZARDS ASSESSMENT NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT SEPTEMBER 24 2010 SYNOPSIS: THE UPPER-LEVEL PATTERN ACROSS THE U.S. IS FORECAST TO AMPLIFY BY EARLY NEXT WEEK, LEADING TO THE POTENTIAL FOR HEAVY RAIN ACROSS THE MID-ATLANTIC/ SOUTHEASTERN STATES AND ABOVE-AVERAGE TEMPERATURES IN THE WEST. AN ACTIVE WEATHER PATTERN IS EXPECTED FOR PARTS OF SOUTHERN ALASKA THIS WEEKEND INTO NEXT WEEK. CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT IN THE WESTERN AND CENTRAL CARIBBEAN THROUGH NEXT WEEK. HAZARDS * HEAVY RAIN FOR THE MID-ATLANTIC, THE CENTRAL/SOUTHERN APPALACHIANS AND THE SOUTHEAST SEP 27-29. * HEAVY RAIN AND POSSIBLE FLOODING FOR FLORIDA AND THE SOUTHEAST U.S. COAST SEP 30-OCT 1. * MUCH ABOVE-AVERAGE TEMPERATURES FOR PARTS OF THE ROCKIES AND GREAT BASIN SEP 28-29. * RIVER FLOODING FOR THE UPPER MISSISSIPPI RIVER BASIN SEP 27-28. * ONGOING RIVER FLOODING FOR PARTS OF THE MIDDLE MISSISSIPPI VALLEY AND CENTRAL PLAINS. * SEVERE DROUGHT FOR SOUTHERN OREGON, NORTHERN ARIZONA, MUCH OF HAWAII, PARTS OF THE UPPER GREAT LAKES, THE MIDDLE AND LOWER MISSISSIPPI VALLEY, THE OHIO VALLEY, THE SOUTHEAST, AND THE MID-ATLANTIC. SOME RELIEF IS EXPECTED FOR MOST AREAS EXCEPT IN THE WEST. DETAILED SUMMARY FOR MONDAY SEPTEMBER 27 - WEDNESDAY SEPTEMBER 29: THE LONGWAVE PATTERN IS EXPECTED TO AMPLIFY THROUGH THIS PERIOD, WITH AN UPPER-LEVEL TROUGH PREDICTED TO DEEPEN OVER THE LOWER MISSISSIPPI VALLEY AND UPPER-LEVEL RIDGING FORECAST TO BECOME ESTABLISHED OVER THE INTERIOR WESTERN CONUS. DOWNSTREAM OF THE TROUGH, INCREASING MOISTURE IS EXPECTED TO CONTRIBUTE TO A HEAVY RAINFALL RISK FOR THE EASTERN CONUS. A RIVER FLOODING HAZARD IS DESIGNATED FOR THE UPPER MISSISSIPPI RIVER BASIN FOR MONDAY AND TUESDAY. HEAVY RAINS THAT HAVE FALLEN PRIOR TO THE ASSESSMENT PERIOD HAS LED TO RAPID RIVER RISES IN THIS REGION. THE BEGINNING OF A PROLONGED PERIOD OF WET WEATHER FOR THE EASTERN CONUS IS EXPECTED TO COMMENCE ON MONDAY. AN AREA OF LOW PRESSURE IS FORECAST TO MOVE NORTHWARD INTO THE CENTRAL APPALACHIANS ON MONDAY. SHOWERS AND THUNDERSTORMS CAPABLE OF HEAVY RAIN ARE LIKELY TO DEVELOP ACROSS THE MID-ATLANTIC, TENNESSEE VALLEY AND THE SOUTHERN/CENTRAL APPALACHIANS ON MONDAY, WITH THIS ACTIVITY EXPECTED TO SPREAD INTO THE CAROLINAS AND THE SOUTHEAST ON TUESDAY AND WEDNESDAY. A MUCH ABOVE-AVERAGE TEMPERATURE HAZARD IS DESIGNATED FOR THE ROCKIES AND GREAT BASIN ON TUESDAY AND WEDNESDAY. DAYTIME TEMPERATURE ANOMALIES OF 16 TO 20 DEGREES FAHRENHEIT ABOVE AVERAGE ARE EXPECTED ACROSS THIS REGION ON TUESDAY, CORRESPONDING TO HIGHS IN THE UPPER 80S TO THE MID 90S. ON WEDNESDAY, MUCH ABOVE-AVERAGE TEMPERATURES ARE EXPECTED TO BE LIMITED TO THE GREAT BASIN. HOT AND DRY CONDITIONS MAY ALSO LEAD TO ENHANCED FIRE DANGER IN THE REGION. A CONTINUED UNSETTLED WEATHER PATTERN IS EXPECTED FOR SOUTHERN ALASKA THROUGH THE PERIOD. A STORM SYSTEM POSSIBLY ENHANCED BY REMNANT ENERGY FROM A TROPICAL CYCLONE CURRENTLY IN THE WESTERN PACIFIC MAY BRING HEAVY RAIN AND/OR HIGH WINDS TO SOUTHERN ALASKA AND THE ALEUTIANS EARLY NEXT WEEK. MODEL UNCERTAINTY PRECLUDES DESIGNATING THESE HAZARDS AT THIS TIME. CONDITIONS ARE EXPECTED TO BE FAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT IN THE ATLANTIC BASIN. WHILE TROPICAL CYCLONE LISA IS NOT EXPECTED TO AFFECT LAND, TROPICAL CYCLONE MATTHEW IS EXPECTED TO MAKE LANDFALL IN BELIZE AND BECOME A REMNANT LOW OVER THE YUCATAN EARLY IN THIS PERIOD. MODEL GUIDANCE INDICATES ADDITIONAL DEVELOPMENT IS POSSIBLE IN THE NORTHWEST CARIBBEAN LATE IN THE PERIOD. PLEASE SEE THE LATEST FORECASTS ISSUED BY THE NATIONAL HURRICANE CENTER AT HTTP://WWW.NHC.NOAA.GOV. FOR THURSDAY SEPTEMBER 30 - MONDAY OCTOBER 04: A LARGE DEGREE OF UNCERTAINTY EXISTS DURING THIS PERIOD, WHICH STEMS FROM INTERACTION BETWEEN AN EASTERN CONUS UPPER-LEVEL TROUGH AND POTENTIAL WESTERN CARIBBEAN TROPICAL CYCLONE ACTIVITY. HEAVY RAIN AND FLOODING FOR FLORIDA AND THE SOUTHEAST U.S. COAST LATE NEXT WEEK APPEARS LIKELY AT THIS TIME, BUT ADDITIONAL HEAVY RAIN AND/OR HIGH WIND HAZARDS MAY ALSO EXTEND FURTHER NORTH LATER IN THE PERIOD. WITH CONTINUED FORECASTS OF AN AMPLIFIED RIDGE IN THE WEST, ABOVE-AVERAGE TEMPERATURES ARE EXPECTED TO CONTINUE. FOR TUESDAY OCTOBER 05 - FRIDAY OCTOBER 08: THE PATTERN FEATURING UPPER-LEVEL TROUGHING ACROSS THE EASTERN STATES ALONG WITH WESTERN CONUS UPPER-LEVEL RIDGING IS FORECAST TO CONTINUE IN THIS PERIOD. HEAVY RAINFALL IN THE EASTERN STATES AND ABOVE-AVERAGE TEMPERATURES ACROSS THE WESTERN CONUS ARE POTENTIAL HAZARDS. THE ATLANTIC TROPICS WILL ALSO NEED TO BE MONITORED FOR TROPICAL DEVELOPMENT. THE DROUGHT AREAS ARE EXPECTED TO REMAIN, THOUGH SOME RELIEF IS EXPECTED IN ALL AREAS EXCEPT IN THE WEST. FORECASTER: ANDREW LOCONTO |