269
FXUS64 KMRX 011805
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
205 PM EDT SAT AUG 1 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 156 PM EDT SAT AUG 1 2026
- SHOWERS AND STORMS WILL MOVE IN TODAY AND CONTINUE TONIGHT INTO
SUNDAY. A FEW STORMS MAY BECOME STRONG TO SEVERE, ESPECIALLY OVER
THE PLATEAU AND THE SOUTHERN TENNESSEE VALLEY LATE SATURDAY INTO
SATURDAY NIGHT. LOCALIZED FLOODING WILL ALSO BE POSSIBLE.
- SCATTERED SHOWERS AND STORMS CAN BE EXPECTED EACH DAY MONDAY
THROUGH FRIDAY, ESPECIALLY DURING THE AFTERNOON HOURS.
DISCUSSION
ISSUED AT 129 AM EDT SAT AUG 1 2026
MODEL RUN TO RUN AGREEMENT IS STILL POOR OVERALL, SO THE DETAILS
EVEN IN THE SHORT TERM ARE NOT AS CERTAIN AS WOULD BE PREFERRED.
HOWEVER, THE BASIC PATTERN IS NOT MUCH IN DOUBT WITH AN UPPER LOW
MOVING OUT OF THE MID MISSISSIPPI VALLEY AND INTO THE OHIO RIVER
VALLEY/SOUTHERN GREAT LAKES REGION THROUGH SUNDAY. A COLD FRONT WILL
APPROACH US FROM THE WEST AND EVENTUALLY MOVE INTO/THROUGH OUR AREA
SATURDAY NIGHT AND/OR SUNDAY. THE DETAILS OF HOW STRONG AND THE
EXACT TRACK OF BOTH THE LOW PRESSURE SYSTEM AND HOW QUICKLY THE
FRONT WILL MOVE INTO AND THROUGH OUR AREA HAVE BEEN HANDLED VERY
INCONSISTENTLY BY THE MODELS. HOWEVER, THERE IS HIGH CONFIDENCE
THAT SHOWERS AND THUNDERSTORMS WILL MOVE INTO OUR AREA LATER TONIGHT
AND THIS MORNING AS MOISTURE SURGES IN WITH THE INCREASING SOUTHERLY
FLOW AND DIVERGENCE ALOFT AHEAD OF THE UPPER TROUGH. THIS
THUNDERSTORM ACTIVITY IS EXPECTED TO BE SUB-SEVERE, AS CAPE WILL BE
MODEST AND THE CONVECTION LIKELY ELEVATED AT FIRST.
CLOUDS AND CONVECTION DURING THE DAY SATURDAY WILL IMPACT HOW MUCH
INSTABILITY DEVELOPS, BUT IT CURRENTLY LOOKS LIKE AT LEAST MODERATE
MLCAPE OF 1000 TO 1500 J/KG WILL DEVELOP OVER WESTERN AREAS DURING
THE AFTERNOON. BY LATE TODAY/THIS EVENING THE FRONT WILL BE MOVING
INTO MIDDLE TN, AND THE CAMS GENERALLY SHOW ADDITIONAL CONVECTION
FIRING AHEAD OF THE FRONT AND MOVING EAST TOWARD OUR AREA. MODELS
HAVE AROUND 20 TO 30 KTS OF EFFECTIVE SHEAR WHICH GIVEN AT LEAST
MODERATE INSTABILITY WOULD SUPPORT ORGANIZATION OF THE CONVECTION
AND THE POTENTIAL FOR SOME STRONG TO SEVERE STORMS WITH DAMAGING
WINDS THE PRIMARY THREAT. THE BEST LOW LEVEL SHEAR LOOKS TO STAY TO
OUR NORTH AND NORTHWEST, BUT THERE IS SUFFICIENT LOW LEVEL SHEAR AND
CLOCKWISE CURVATURE OF THE HODOGRAPH THAT A TORNADO CANNOT BE RULED
OUT ESPECIALLY IF THE CAPE AND SHEAR POTENTIAL IS MAXIMIZED. THE
SEVERE POTENTIAL SHOULD BE HIGHEST FOR OUR PLATEAU AND SOUTHERN
VALLEY COUNTIES WHERE THE CONVECTION WILL ARRIVE FIRST AND SURFACE
CAPE WILL HAVE LESS TIME TO DECREASE FROM LOSS OF SOLAR HEATING. THE
LOW LEVEL JET WILL BE OUT OF THE SOUTH AND SOUTHEAST ACROSS THE
MOUNTAINS SATURDAY AND SATURDAY NIGHT, WITH DOWNSLOPE FLOW INTO THE
VALLEY. IN FACT, WE WILL LIKELY SEE GUSTY WINDS IN THE USUAL HIGHER
MOUNTAIN ELEVATION AND FOOTHILL AREAS WITH SOME MOUNTAIN WAVE
ENHANCEMENT OF THE WINDS, ALTHOUGH IT GENERALLY SHOULD STAY SUB-WIND
ADVISORY LEVEL. GIVEN THIS DOWNSLOPE FLOW AS WELL AS THE LATER
ARRIVAL OF THE CONVECTION IN OUR CENTRAL AND NORTHERN/EASTERN AREAS,
IT IS NOT SURPRISING THAT THE CAMS QUICKLY WEAKEN THE CONVECTION AS
IT PROGRESSES FURTHER EAST ACROSS OUR AREA.
IN ADDITION TO THE SEVERE THREAT, GIVEN THE ABUNDANT MOISTURE WITH
PWAT VALUES NEAR OR EXCEEDING 2 INCHES FOR SATURDAY INTO SATURDAY
NIGHT VERY HEAVY RAINFALL AND LOCALIZED FLOODING WILL ALSO BE
POSSIBLE, ESPECIALLY ACROSS THE PLATEAU AND SOUTHERN PORTIONS OF OUR
AREA.
DEPENDING ON HOW QUICKLY THE FRONT CLEARS OUR AREA, A MARGINAL
SEVERE STORM THREAT MAY CONTINUE INTO SUNDAY OVER OUR NORTHEAST
COUNTIES AHEAD OF THE BOUNDARY WHERE SIGNIFICANT EFFECTIVE SHEAR AND
INSTABILITY WILL BE LINGERING AHEAD OF THE FRONT. BEHIND THE FRONT,
ANY SHOWERS AND STORMS SHOULD BE MORE ISOLATED TO SCATTERED AND
WEAKER SUNDAY.
THE LATER PERIODS CONTINUE TO FEATURE SIGNIFICANT CHANCES FOR
SHOWERS AND STORMS EACH DAY MONDAY THROUGH FRIDAY BUT WITH THE
HIGHEST CHANCES EARLY IN THE WEEK IN RESPONSE TO A MEANDERING WEAK
UPPER LOW THAT MOST MODELS LEAVE BEHIND OVER THE REGION. MODELS
STILL DISAGREE ON PLACEMENT AND MOVEMENT OF THE UPPER LOW, AND SOME,
WHILE IN THE MINORITY, WOULD SUGGEST A QUICKER RETURN TO DRIER AND
WARMER CONDITIONS. WE WILL HAVE TO SEE AS WE GET CLOSER.
AVIATION
(18Z TAFS)
ISSUED AT 156 PM EDT SAT AUG 1 2026
RAIN SHIELD IS MOVING FROM THE CENTRAL TO EASTERN PORTIONS OF THE
FORECAST AREA AT THIS TIME. THE BACK EDGE SHOULD BE THROUGH TYS
WITHIN THE NEXT HOUR OR SO, AND ESTIMATED AROUND 20/21Z FOR TRI.
REDUCED VISIBILITY AND OCCASIONAL CIG REDUCTIONS CANNOT BE RULED
OUT WITH THIS ACTIVITY. UNSETTLED PATTERN CONTINUES AS ADDITIONAL
SHOWERS AND STORMS DEVELOP AND ADVECT WEST TO EAST THIS EVENING
INTO THE OVERNIGHT HOURS. THUNDERSTORM CHANCES ARE GREATEST AT
CHA/TYS. LINGERING MVFR CONDITIONS ARE POSSIBLE BEHIND THE
ACTIVITY OVERNIGHT. HOWEVER, THE LOWEST UNCERTAINTY IS AT TRI DUE
TO EXPECTED DOWNSLOPING. MOS AND LAMP GUIDANCE IS AGGRESSIVE WITH
LOW CIGS WHILE HREF PROBABILITIES ARE LESS THAN 20% AT TRI.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 72 86 70 85 / 90 50 10 50
KNOXVILLE MCGHEE TYSON AIRPORT, TN 72 86 70 84 / 80 60 40 60
OAK RIDGE, TN 71 85 69 84 / 90 70 30 60
TRI CITIES AIRPORT, TN 69 85 67 82 / 70 90 60 50
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...99
AVIATION...KRS
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