980
FXUS64 KMRX 091641
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
1241 PM EDT SAT AUG 9 2025
..NEW DISCUSSION, AVIATION
DISCUSSION
ISSUED AT 1231 PM EDT SAT AUG 9 2025
KEY MESSAGES:
1. WARM, MOSTLY DRY WEEKEND WITH NEAR NORMAL TEMPERATURES.
ISOLATED CONVECTION ACROSS THE MOUNTAINS.
2. INCREASING MOISTURE BY THE MIDDLE OF NEXT WEEK WITH INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS, ESPECIALLY DURING THE
AFTERNOON HOURS. HEAVY RAIN RATES POSSIBLE MID-WEEK.
DISCUSSION:
WE REMAIN UNDER THE INFLUENCE OF UPPER-LEVEL RIDGING ACROSS THE
APPALACHIANS WITH A TROPICAL LOW PRESSURE SYSTEM NEAR FLORIDA AND
THE FAR SOUTHEAST CONUS WITH TROUGHING ACROSS THE NORTHERN GREAT
PLAINS. THIS IS RESULTING IN NEAR NORMAL TEMPERATURES AND MOSTLY
DRY WEATHER ACROSS THE REGION. A FEW DIURNAL SHOWERS OR
THUNDERSTORMS WILL BE POSSIBLE, BUT MOST AREAS WILL REMAIN DRY
THIS WEEKEND.
RIDGING ACROSS THE WESTERN ATLANTIC WILL RETROGRADE TOWARDS THE
SOUTHEAST CONUS EARLY THIS WEEK. INCREASING SOUTHWESTERLY FLOW
AROUND THE WESTERN PERIPHERY OF THE RIDGE AND AHEAD OF A SHORTWAVE
TROUGH AND FRONTAL BOUNDARY WILL PLACE OUR REGION IN A MUCH MORE
HUMID, MOISTURE RICH ENVIRONMENT BY WEDNESDAY AND THURSDAY. THIS
WILL RESULT IN INCREASING RAIN CHANCES, MAINLY DURING THE
AFTERNOON HOURS. LREF GUIDANCE SHOWS A GREATER THAN 1 IN 4 CHANCE
OF PW VALUES ABOVE 2.0 INCHES, AND A GREATER THAN 80% CHANCE OF
PW VALUES GREATER THAN 1.8 INCHES. CONSIDERING THE LIMITED
RESOLUTION OF MUCH OF THE MODELS AND ENSEMBLES GOING INTO THE
BLEND AT THIS TIME STEP, IT'S LIKELY THAT HIGH PW VALUES WILL
OCCUR ACROSS THE TENNESSEE VALLEY. THIS APPEARS TO BE FROM A
TROPICAL PLUME OF MOISTURE MOVING NORTHWARD OUT OF THE GULF AND
INTO THE TENNESSEE AND OHIO VALLEYS. THE GFS SHOWS THIS MOISTURE
TO BE 2 TO 3 SIGMA ABOVE THE MEAN, AND NAEFS DATA IS PLACING IT
AROUND THE 97-99 PERCENTILE OF THE CLIMATOLOGY. THIS TROPICAL-
LIKE MOISTURE WILL RESULT IN MORE WIDESPREAD CONVECTION WITH
LOCALLY HEAVY RAIN RATES OF 2 TO 3 INCHES PER HOUR. LOCALIZED
FLASH FLOODING WILL BE POSSIBLE, ESPECIALLY FOR URBAN AND FLOOD
PRONE LOCATIONS. INSTABILITY WILL BE TRENDING UP WITH THE
INCREASING MOISTURE AS MLCAPE VALUES BEGIN TO REACH 2000 TO 2500
J/KG EACH AFTERNOON. HEAVY RAIN RATES, FREQUENT LIGHTNING, AND
GUSTY WINDS WOULD BE EXPECTED WITH THE STRONGER THUNDERSTORMS, BUT
WITH WEAK SHEAR AND LIMITED DCAPE, THE SEVERE THUNDERSTORM RISK
IS LOW.
LATE WEEK, UNCERTAINTY IS CONSIDERABLE; HOWEVER, AT THIS TIME, THE
MOST PROBABLE OUTCOME TAKES THE PLUME OF TROPICAL MOISTURE
NORTHEAST OF OUR AREA AS THE SHORTWAVE TROUGH ACROSS THE OHIO
VALLEY EJECTS EASTWARDS. IT WILL STILL BE HUMID ACROSS OUR AREA,
BUT PW VALUES WILL BE SLIGHTLY LOWER AND CLOSER TO NORMAL FOR THIS
TIME OF YEAR. NORMAL LATE-SUMMER DIURNAL CONVECTION IS STILL
EXPECTED ACROSS THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS
WITH HIGHEST PROBABILITIES ACROSS THE HIGHER ELEVATIONS OF THE
MOUNTAINS AND PLATEAU.
AVIATION
(18Z TAFS)
ISSUED AT 1231 PM EDT SAT AUG 9 2025
VFR CONDITIONS ARE FORECAST WITH ISOLATED CONVECTION NEAR THE
MOUNTAINS. STILL, THE MAJORITY OF THIS CONVECTION IS FORECAST TO
REMAIN AWAY FROM TERMINALS WITH ONLY A 20 PERCENT PROBABILITY OF
CONVECTION IN THE VICINITY OF TYS AND CHA. SCT CLOUDS AROUND 2500
TO 3500 FT MAY RESULT IN SOME BRIEF BKN MVFR CIGS NEAR TYS AND CHA
THIS AFTERNOON, BUT OTHERWISE, VFR CIGS PREVAIL. BECAUSE OF THE
VERY LOW PROBABILITIES FOR PRECIPITATION LESS THAN 20 PERCENT AT
CHA AND TYS, WILL NOT MENTION SHRA OR TSRA IN TAF. PATCHY FOG IS
EXPECTED OVERNIGHT AND EARLY SUNDAY, MAINLY NEAR TRI. WINDS
REMAINS LIGHT AND VARIABLE.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 69 89 71 88 / 0 20 10 40
KNOXVILLE MCGHEE TYSON AIRPORT, TN 67 90 69 90 / 0 10 10 30
OAK RIDGE, TN 67 90 69 90 / 0 10 0 30
TRI CITIES AIRPORT, TN 61 87 66 88 / 0 10 10 30
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
SHORT TERM...JB
LONG TERM....JB
AVIATION...JB
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