US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300
PM EDT MAY 05 2009
SYNOPSIS: FROM FRIDAY INTO SATURDAY, LOW
PRESSURE SHOULD TRACK EAST ALONG A FRONTAL BOUNDARY FROM THE SOUTHERN PLAINS
INTO THE TENNESSEE VALLEY AND CENTRAL APPALACHIANS. ON SUNDAY, LOW PRESSURE
EXITS THE NORTHEAST AS HIGH PRESSURE BUILDS SOUTH AND THE AFOREMENTIONED
FRONTAL BOUNDARY SHIFTS SOUTH TOWARDS THE GULF COAST. AN UPPER-LEVEL RIDGE
SHOULD REMAIN DOMINANT OVER THE SOUTHWEST.
HAZARDS - FROM
MAY 8 - 9, HEAVY RAIN CAN BE EXPECTED ACROSS THE OZARKS, TENNESSEE VALLEY, AND
CENTRAL APPALACHIANS.
- ON MAY 8, SEVERE WEATHER IS FORECAST IN EASTERN OKLAHOMA, NORTHEAST TEXAS,
AND ARKANSAS.
- FROM MAY 8 - 11, MUCH ABOVE NORMAL TEMPERATURES ARE EXPECTED IN THE
SOUTHWEST.
- ONGOING FLOODING FOR PORTIONS OF THE NORTHERN PLAINS AND UPPER MIDWEST
INCLUDING THE RED RIVER VALLEY OF THE NORTH, THE SHEYENNE RIVER AND THE JAMES
RIVER.
- ONGOING FLOODING FOR THE ILLINOIS RIVER.
- ONGOING RIVER FLOODING IN PARTS OF ALASKA.
- SEVERE DROUGHT PERSISTS ACROSS PARTS OF CALIFORNIA, NEVADA, NEW MEXICO,
TEXAS, WISCONSIN, AND FLORIDA.
DETAILED SUMMARYFOR FRIDAY MAY 08 - SUNDAY MAY 10: A LOW AMPLITUDE SHORTWAVE
TROUGH SHOULD RAPIDLY TRACK FROM THE PLAINS INTO THE NORTHEAST. ON FRIDAY,
ABUNDANT MOISTURE, STRONG INSTABILITY, AND SUFFICIENT SHEAR SHOULD SUPPORT
SEVERE THUNDERSTORM DEVELOPMENT IN THE EASTERN PARTS OF THE SOUTHERN PLAINS.
MODEL GUIDANCE SUGGESTS THAT A MESOSCALE CONVECTIVE SYSTEM (MCS) MAY TRACK FROM
THE OZARKS INTO THE TENNESSEE VALLEY ON FRIDAY NIGHT. HEAVY RAINFALL IN EXCESS
OF 3 INCHES AND ADDITIONAL FLOODING CAN BE EXPECTED IN ARKANSAS AND TENNESSEE.
LOCALLY HEAVY RAIN AND RIVER FLOODING MAY ALSO AFFECT PARTS OF THE CENTRAL
APPALACHIANS AND MID-ATLANTIC.
DESPITE RECENT DRYNESS, RIVER FLOODING ALONG THE RED, SHEYENNE, AND JAMES
RIVERS IN THE NORTHERN PLAINS CONTINUES AND SHOULD LINGER INTO NEXT WEEK.
FLOODING WILL ALSO PERSIST ALONG THE ILLINOIS RIVER.
ACROSS THE SOUTHERN FLORIDA PENINSULA, EXTREME DROUGHT HAS EXPANDED AND
NUMEROUS WILDFIRES HAVE DEVELOPED IN RECENT WEEKS. IN THE BIG CYPRESS NATIONAL
PRESERVE IN SOUTHWEST FLORIDA, A LARGE WILDFIRE (MORE THAN 30,000 ACRES BURNT)
SPARKED BY LIGHTNING IN LATE APRIL IS 95% CONTAINED.
DUE TO RIDGING ALOFT, MUCH ABOVE NORMAL TEMPERATURES ARE FORECAST IN MUCH
OF THE SOUTHWEST. ON FRIDAY, MAXIMUM TEMPERATURES WILL RANGE FROM 95 – 105 °F
IN SOUTHEAST NEW MEXICO AND WESTERN TEXAS BEFORE RELIEF FROM THE HEAT ARRIVES
THIS WEEKEND. HOT TEMPERATURES, WITH MAXIMUM TEMPERATURES REACHING 100 °F,
SHOULD CONTINUE ACROSS THE DESERT SOUTHWEST.
DURING THE PAST WEEK, SNOWMELT TRIGGERED RIVER FLOODING IN PARTS OF ALASKA.
FLOODING CONTINUES ALONG THE CHENA AND TANANA RIVERS AT OR OUTSIDE OF
FAIRBANKS. ADDITIONAL RIVER FLOODING REMAINS POSSIBLE.
FOR MONDAY MAY 11
- FRIDAY MAY 15: THE GREATEST UNCERTAINTY IS THE LOCATION OF A FRONTAL
BOUNDARY THAT HAS RECENTLY PLAGUED THE MID-SOUTH WITH FREQUENT PERIODS OF HEAVY
RAIN AND FLOODING. THE OPERATIONAL RUN OF THE 0Z ECMWF CONTINUES THE LIKELIHOOD
OF HEAVY RAINFALL IN THE OZARKS AND TENNESSEE VALLEY, WHILE THE OPERATIONAL RUN
OF THE 0Z GFS INDICATES A DRIER WEATHER PATTERN. DUE TO CONFLICTING SIGNALS
FROM THE MODELS, A HEAVY RAINFALL HAZARD IS NOT DEPICTED BEYOND MAY 9. HOWEVER,
THE POTENTIAL FOR HEAVY RAINFALL AND ADDITIONAL FLOODING SHOULD BE CLOSELY
MONITORED IN THE OZARKS AND TENNESSEE VALLEY.
LATER NEXT WEEK, AN INCREASE IN 500-HPA HEIGHTS ACROSS THE SOUTH-CENTRAL
CONUS SHOULD RESULT IN A GRADUAL DRYING TREND FOR THE EXCESSIVELY WET AREAS OF
THE MID-SOUTH, AND EXPAND ABOVE NORMAL TEMPERATURES TO INCLUDE THE SOUTHERN
PLAINS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. IT SHOULD BE NOTED THAT THE
OPERATIONAL RUN OF THE 12Z GFS INDICATES A HIGHLY AMPLIFIED PATTERN WITH 500
H-PA HEIGHTS GREATER THAN 588 DM IN THE SOUTHEAST BY THE MIDDLE PART OF NEXT
WEEK. THIS UPPER-LEVEL PATTERN COULD BRING A SPELL OF MUCH ABOVE NORMAL
TEMPERATURES TO THE SOUTHEAST.
FOR SATURDAY MAY 16 - TUESDAY MAY
19: THE EXPECTED LONGWAVE PATTERN OF ZONAL FLOW NEAR THE U.S./CANADA BORDER
WOULD SHIFT THE PRIMARY STORM TRACK INTO THE UPPER MIDWEST. THE INCREASE IN
500-HPA HEIGHTS NOTED IN THE 0Z AND 6Z GFS ENSEMBLE MEAN SOLUTIONS AT D+11
SHOULD BRING ABOVE NORMAL TEMPERATURES TO MUCH OF THE CENTRAL AND EASTERN U.S.
NO DROUGHT RELIEF IS EXPECTED IN FLORIDA AND WILDFIRE DANGER WILL REMAIN
ELEVATED. THE MEDIAN ONSET OF THE RAINY SEASON IN FLORIDA IS MAY 21.
FORECASTER: BRAD PUGH
$$