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

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS64 KMRX 222024 AFDMRX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MORRISTOWN TN 324 PM EST MON DEC 22 2014 .SHORT TERM (TODAY THROUGH WEDNESDAY)...
-- Changed Discussion --
INCREASING LOW-LEVEL JET ACROSS THE TENNESSEE VALLEY IN RESPONSE TO AN UPPER WAVE MOVING ACROSS THE AREA WILL ENHANCE THE ISENTROPIC LIFT. INCREASING DYNAMICS IS ALREADY INCREASING CONVECTION OVER THE PLATEAU AND ALABAMA. FORECAST SOUNDING SHOWS ELEVATED INSTABILITY...SO HAVE INCLUDED THUNDERSTORMS FOR THE SOUTHERN HALF OF THE AREA. PLENTY OF LOW-LEVEL MOISTURE PULLING INTO THE SOUTHERN VALLEY WILL ALSO PRODUCE EXTENSIVE FOG AND DRIZZLE OVERNIGHT ACROSS THE CHA AREA. FOR TUESDAY...DOWNSLOPING WINDS WILL HELP CLEAR OUT THE CLOUDS OVER THE NORTHERN HALF OF THE VALLEY WHILE THE SOUTHERN HALF STAYS WITHIN LOW-CLOUDS AND MORNING FOG/DRIZZLE. A STRONG JET OVER THE OHIO VALLEY AND JET ASSOCIATED WITH INCOMING UPPER TROUGH WILL PRODUCE STRONG UPPER DIVERGENCE OVER THE AREA LATE TUESDAY AND TUESDAY NIGHT. AGAIN...GIVEN ELEVATED INSTABILITY EXPECTED WIDE SPREAD SHOWERS AND CHANCE OF THUNDERSTORMS. SOME OF THE RAIN COULD BE HEAVY OVER THE AREA...ESPECIALLY PLATEAU AND SOUTHEAST TENNESSEE FOR TUESDAY NIGHT. FOR WEDNESDAY...COLD FRONT MOVES THROUGH THE AREA PRODUCING WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS. CONVECTION WILL END FROM WEST TO EAST AS FRONTAL BOUNDARY MOVES ACROSS THE REGION. .LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY)...A BRIEF SHOT AT LIGHT SNOW STILL POSSIBLE LATE CHRISTMAS EVE INTO EARLY CHRISTMAS MORNING. NO ACCUMULATION EXPECTED EXCEPT FOR MAYBE UP TO AN INCH OR SO ACROSS THE HIGHEST ELEVATIONS. THEN A WEEKEND SYSTEM APPROACHES THAT THE MODELS STILL AREN`T HANDLING WELL. BY WEDNESDAY EVENING THE BULK OF THE PRECIPITATION WILL HAVE PASSED TO OUR EAST AS WE AWAIT THE PASSAGE OF THE COLD FRONT. THE GFS AND THE NAM BOTH SHOW A DRY SLOT BETWEEN THE FRONTAL PASSAGE AND THE FINAL PUSH OF PRECIP INTO THE AREA. THIS MEANS THERE WILL LIKELY BE A BREAK BETWEEN THE LIQUID PRECIP AND ANY SNOW THAT OCCURS. THE WRAP AROUND MOISTURE AND ASSOCIATED SHORTWAVE COMES IN CLOSE TO MIDNIGHT. AS OF NOW...IT LOOKS LIKE LOCATIONS NORTH OF 1-40 MAY BE THE ONLY ONES TO SEE ANY SNOW. THE LOWER ELEVATIONS ACROSS THE SOUTHERN VALLEY APPEAR TO BE TOO WARM FROM THE LATEST GUIDANCE. AREAS NORTH OF I-40 MAY SEE LIGHT SCATTERED SNOW SHOWERS/FLURRIES AFTER MIDNIGHT AND INTO EARLY CHRISTMAS MORNING...THE BEST CHANCES WILL BE ACROSS NETN AND SWVA. PRECIP QUICKLY MOVES OFF TO THE NORTHEAST DURING THE MID TO LATE MORNING HOURS OF CHRISTMAS DAY AND SOME AREAS MAY EVEN SEE A CHANGE OVER BACK TO LIGHT RAIN/DRIZZLE BEFORE THE PRECIP COMPLETELY EXITS. AS THE DAY PROGRESSES THE CLOUDS SHOULD ERODE FROM SW TO NE...BRINING SUNSHINE TO MOST AREAS BY MID TO LATE AFTERNOON. WE SHOULD STAY DRY FROM THURSDAY EVENING THROUGH MOST OF THE DAY FRIDAY WITH SUNSHINE BRIEFLY RETURNING. BRING PRECIP BACK IN FRIDAY NIGHT AND KEEP IT INTO MONDAY. MODELS STILL DOING A VERY POOR JOB HANDLING THIS NEXT SYSTEM. THE ECMW LOOKS WET WITH A POTENT SHORTWAVE SWINGING THROUGH WHILE THE GFS IS MUCH DRIER WITH NOTHING MORE THAN A WEAK FRONT CRUISING THROUGH. WILL GO WITH A BLEND OF POPS BETWEEN THE GFS AND ECMW UNTIL THEY BETTER AGREE. DURING THIS TIME FRAME...IT MAY BE COLD ENOUGH TO SEE SOME LIGHT SNOW ACROSS ACROSS THE HIGHER TERRAIN.
-- End Changed Discussion --
&& .PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
CHATTANOOGA AIRPORT, TN 45 55 53 62 / 70 90 100 90 KNOXVILLE MCGHEE TYSON AIRPORT, TN 43 61 50 65 / 60 80 100 100 OAK RIDGE, TN 43 58 52 63 / 60 80 100 90 TRI CITIES AIRPORT, TN 37 60 48 65 / 50 50 80 100
-- End Changed Discussion --
&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.