Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 231920 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 320 PM EDT THU MAY 23 2013 .SHORT TERM (TONIGHT AND FRIDAY)...
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CURRENT SURFACE ANALYSIS SHOWS A WEAK COLD FRONT GENERALLY ALONG THE CUMBERLAND PLATEAU...WITH RADARS REVEALING SCATTERED CONVECTION DEVELOPING OVER EASTERN KY AND SOUTHWEST VA. A MARGINALLY UNSTABLE AIR MASS WILL CONTINUE OVER THE FORECAST AREA INTO THIS EVENING...AS A BROAD UPPER-LEVEL TROUGH AMPLIFIES OVER THE EASTERN HALF OF THE NATION. MODELS INDICATE THAT THIS UPPER TROUGH WILL CONTINUE TO PRODUCE SCATTERED SHOWERS AFTER MIDNIGHT...WITH MUCH COOLER AND DRIER AIR MOVING INTO THE FORECAST AREA BEHIND THE FRONTAL BOUNDARY ON FRIDAY. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS ARE IN GENERAL AGREEMENT FOR TONIGHT AND FRIDAY...BUT WILL COMPROMISE WHERE SOME SLIGHT DIFFERENCES ARE NOTED. .LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)...HIGH PRESSURE IN NW FLOW PATTERN TO DROP TEMPERATURES MUCH BELOW NORMAL FRIDAY NIGHT WITH FROST POSSIBLE NE SECTIONS AND NORTHERN AND CENTRAL MOUNTAINS. SW NORTH CAROLINA VALLEYS COULD ALSO DROP TO UPPER 30S. REFERRED TO FROST IN HAZARDOUS WEATHER OUTLOOK AND COULD ISSUE AN ADVISORY AS EARLY AS FRIDAY MORNING IF CONFIDENCE IS HIGH. WILL GENERALLY FOLLOW COOLER MAV NUMBERS FRIDAY NIGHT. SATURDAYS HIGHS ONLY A FEW DEGREES WARMER THAN FRIDAY AS SURFACE HIGH MOVES SOUTHEAST FROM THE UPPER MIDWEST INTO THE EASTERN GREAT LAKES AND OHIO AND TENNESSEE VALLEYS. STILL SLIGHT COLD AIR ADVECTION WITH NORTHERLY FLOW. DEW POINTS WILL BE IN THE 30S TO LOWER 40S WHICH WILL KEEP RH VALUES LOW FOR THIS TIME OF YEAR. UPPER RIDGE OVER THE CENTRAL STATES SATURDAY BEGINS TO SHIFT EAST WITH MOISTURE RETURNING TO THE MID MS VALLEY AS WESTERN PART OF COLD FRONT MOVES BACK NORTH AS WARM FRONT. WITH FLOW AROUND THE RIDGE CLOUDS BEGIN TO INCREASE SUNDAY AND SUNDAY NIGHT SHORTWAVE ENERGY MOVING AROUND RIDGE AND INCREASED MOISTURE WILL BRING CHANCE OF SHOWERS AND THUNDERSTORMS TO THE REGION MAINLY AFTERNOON AND EVENINGS MONDAY AND TUESDAY AND TO A LESSER EXTENT WEDNESDAY AND THURSDAY AS RIDGE STRENGTHENS OVER THE GULF COAST AND TN VALLEY. TEMPERATURES WILL BE ON A SLOW WARMING TREND AS WARMER AIR FROM RIDGE SETTLES OVER THE TN VALLEY. LOWS WILL RISE BACK TO THE MID 50S TO LOWER 60S TUESDAY THROUGH THURSDAY WITH HIGHS BACK TO THE UPPER 70S TO LOWER 80S NORTH AND LOWER TO MID 80S SOUTH.
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&& .PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN 56 74 46 78 50 / 20 0 0 0 0 KNOXVILLE AIRPORT, TN 54 70 43 75 49 / 30 0 0 0 0 OAK RIDGE, TN 54 69 42 74 48 / 30 0 0 0 0 TRI CITIES AIRPORT, TN 51 66 35 72 42 / 30 0 0 0 10
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DMG/TD

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