349  
FXUS64 KHUN 201113 AAA  
AFDHUN  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE HUNTSVILLE AL  
613 AM CDT MON MAY 20 2013  
   
UPDATE
 
 
FOR 12Z TAFS  
 

 
   
DISCUSSION
 
 
/ISSUED 402 AM CDT MON MAY 20 2013/  
AN UNSEASONABLY DEEP MID/UPPER LOW OVER THE NORTHERN PLAINS HELPED  
TO PRODUCE AN EPISODE OF SEVERE WEATHER ACROSS THE GREAT PLAINS. A  
REPEAT IS EXPECTED TODAY A BIT FURTHER EAST...AS THIS LOW SLOWLY  
TRACKS TO THE EAST. HOWEVER...BROAD UPPER RIDGING OVER THE EAST COAST  
WAS HELPING TO BRING WARM CONDITIONS ACROSS THE MOST OF THE DEEP  
SOUTH. A WEAK DISTURBANCE IN THIS RIDGE...NOTED FROM GEORGIA TO  
VIRGINIA WAS RESPONSIBLE FOR THUNDERSTORMS AND HEAVY RAINFALL...  
MAINLY JUST TO OUR EAST. YESTERDAY...DOPPLER RADAR INDICATED THIS  
SYSTEM LIKELY PRODUCED OVER 5 INCHES ACROSS PARTS OF EASTERN TN...NW  
GA...AND FAR NE AL. RESIDUAL MOISTURE FROM THAT RAIN HAS RESULTED IN  
AREAS OF FOG...SOME LOCALLY DENSE AFFECTING PARTS OF NE ALABAMA.  
LIGHTER FOG/MIST WAS DEVELOPING ELSEWHERE. OVERNIGHT LOWS SO FAR HAVE  
FALLEN INTO THE UPPER 50S TO UPPER 60S WITH LIGHT WINDS.  
 
THE UPPER DISTURBANCE EAST OF THE REGION SHOULD PROGRESS FURTHER TO  
THE EAST TODAY...HELPING TO END RAIN CHANCES ACROSS THIS PART OF THE  
TENNESSEE VALLEY TODAY. WITH UPPER RIDGING IN PLACE...AND SURFACE  
HIGH PRESSURE TO OUR EAST...MORE WARM/MUGGY CONDITIONS ARE EXPECTED  
TODAY. HIGHS SHOULD WARM INTO THE MID/UPPER 80S UNDER PARTLY CLOUDY  
SKIES. SOMEWHAT WARMER CONDITIONS ARE FORECAST FOR TUE...WITH HIGHS  
NEARING 90 ACROSS PARTS OF NW ALABAMA. A SOUTHERLY 5-15 MPH FLOW WILL  
CONTINUE A FEED OF MOISTURE ACROSS THE REGION. SURFACE DEWPOINTS ARE  
EXPECTED TO RISE INTO THE MID/UPPER 60S TODAY...AND MID 60S ON TUE...  
WITH CORRESPONDING HEAT INDICES INTO THE UPPER 80S/LOWER 90S.  
 
THE SYSTEM FORECAST TO BRING MORE STRONG STORMS TO THE GREAT PLAINS  
TODAY AND ON TUE. AS A COLD FRONT WITH THIS SYSTEM NEARS...RAIN  
CHANCES WILL RETURN TO THIS REGION TUE AFTERNOON...WITH A SLIGHT  
CHANCE OF SHOWERS/THUNDERSTORMS. CHANCES FOR CONVECTION WILL INCREASE  
FOR THE ENTIRE AREA TUE NIGHT INTO THUR...AS THE FRONT GETS EVER  
CLOSER. GIVEN THE PRECIP WILL BE MORE SHOWERY IN CHARACTER...WILL  
HOLD OFF ON LIKELY POPS THIS GO AROUND FOR WED. SOME OF THE STORMS  
PRECEDING THE COLD FRONT COULD BECOME STRONG...WITH GUSTY WINDS...  
SMALL HAIL AND HEAVY RAINFALL THE PRIMARY THREATS. THE STRONGER SHEAR  
AND OTHER DYNAMICS WITH THIS SYSTEM SHOULD REMAIN TO OUR NORTH.  
 
THE FRONT EAST OF THE VALLEY THU/FRI WILL RESULT IN RAIN CHANCES  
DECREASING BY THE TIME THE NEXT WEEKEND ARRIVES. CANADIAN HIGH  
PRESSURE FOLLOWING THE FRONT WILL BRING BRING SLIGHTLY COOLER HI/LO  
TEMPS FOR THE WEEKEND...WITH VALUES CLOSE TO SEASONABLE LEVELS.  
 
RSB  
 

 
   
AVIATION... FOR 12Z TAFS
 
 
LOW CLOUDS RAPIDLY DEVELOPING/ADVECTING ACROSS NRN AL WITH CIGS  
GENERALLY BETWEEN 008-015 AGL. BELIEVE MVFR CIGS /1000-2000FT/ WILL  
PREVAIL...BUT COULD SEE PERIODIC DIPS TO IFR CAT (NOT ENOUGH TO  
MENTION AT EITHER TERMINAL). SHORT RANGE /RAP/ MODELS SHOWING  
MOISTURE AND LOW CIGS COULD HANG AROUND THROUGH 15-17Z. BY 17Z...SRLY  
WINDS WILL PICK UP AND HEATING WILL DISSIPATE MAJORITY OF SHALLOW LOW  
CLOUDS. VFR CONDITIONS WILL THEN PREVAIL THROUGH 12Z/TUES...THOUGH  
LOW CLOUDS AND SHALLOW FOG COULD REDEVELOP BRIEFLY ONCE AGAIN TOWARD  
DAYBREAK.  
 
DJN.83  
 

 
   
HUN WATCHES/WARNINGS/ADVISORIES
 
 
AL...NONE.  
TN...NONE.  

 
 

 
 
FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE  
AT WEATHER.GOV/HUNTSVILLE.  
 
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