064
FXUS64 KMRX 310530
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
130 AM EDT FRI JUL 31 2026
..NEW DISCUSSION, AVIATION
KEY MESSAGES
UPDATED AT 118 AM EDT FRI JUL 31 2026
- DRY WEATHER WITH SEASONABLE TEMPERATURES AND RELATIVELY
COMFORTABLE HUMIDITY FRIDAY.
- A LOW CHANCE FOR A FEW STRONG STORMS SATURDAY EVENING/NIGHT, WITH
LOCALIZED FLOODING ALSO POSSIBLE.
- THE WET PATTERN THAT SETS UP THIS WEEKEND MAY CONTINUE WELL INTO
NEXT WEEK.
DISCUSSION
ISSUED AT 118 AM EDT FRI JUL 31 2026
SURFACE HIGH PRESSURE CENTERED TO OUR NORTH WILL PROVIDE US WITH
ANOTHER DRY DAY FRIDAY AS IT SLIDES SLOWLY EAST. A MOSTLY SUNNY SKY
AND RELATIVELY COMFORTABLE TEMPERATURES/HUMIDITY FOR LATE JULY CAN
BE EXPECTED FRIDAY, ALTHOUGH HIGH TEMPERATURES WILL BE A COUPLE
DEGREES WARMER THAN THEY WERE THURSDAY.
MODELS ARE STRUGGLING WITH THE WEEKEND SYSTEM, WITH A SOMEWHAT
UNEVEN BUT NOTICEABLE TREND TO KEEP THE LOW PRESSURE SYSTEM AND
BETTER FORCING A BIT FURTHER NORTH. WITH THE POOR MODEL CONSISTENCY,
THE CONFIDENCE LEVEL IN THE DETAILS IS STILL LACKING. AT THIS TIME,
MODELS GENERALLY SHOW DEEP MOISTURE INCREASING SATURDAY WITH PWAT
VALUES APPROACHING OR EXCEEDING 2 INCHES ACROSS MUCH OF THE AREA AS
A LOW PRESSURE SYSTEM TRACKS INTO THE OHIO VALLEY AND/OR SOUTHERN
GREAT LAKES REGION. THIS SYSTEM PULLS A COLD FRONT TOWARD US DURING
THE DAY, WITH IT LIKELY MOVING THROUGH OUR AREA SATURDAY NIGHT/EARLY
SUNDAY. THIS SCENARIO WOULD LIKELY RESULT IN AN INITIAL ROUND OF
SHOWERS/STORMS THAT MOVES IN DURING THE MORNING WITH THE PASSAGE OF
A SHORTWAVE TROUGH, WITH THIS CONVECTION POSSIBLY ELEVATED AND
LIKELY SUB-SEVERE. A LINE OF CONVECTION THEN WOULD FORM IN THE
AFTERNOON TO OUR WEST NEAR THE COLD FRONT AND CLOSER TO THE MAIN
UPPER TROUGH AXIS. THE NAM (WHICH HAS MUCH MORE CAPE THAN THE GFS)
IS QUITE VIGOROUS IN DEVELOPING THIS CONVECTION AS IT CROSSES MIDDLE
TN, BUT BY THE TIME THE CONVECTION REACHES OUR AREA (WELL AFTER
SUNSET) THE NAM SHOWS A SIGNIFICANT WEAKENING TREND AS IT MOVES INTO
OUR AREA WITH THE DECREASING CAPE, THE MAIN UPPER JET SUPPORT WELL
TO OUR NORTH, AND DOWNSLOPE LOW LEVEL FLOW OFF THE EASTERN
MOUNTAINS. WHILE THERE IS SOME DEEP LAYER SHEAR PRESENT, THE
NIGHTTIME ARRIVAL WOULD LIMIT SURFACE-BASED INSTABILITY. ENSEMBLE
JOINT PROBABILITY OF CAPE > 500 J/KG AND EFFECTIVE SHEAR > 30 KT IS
UNDER 20% IN OUR AREA SATURDAY EVENING INTO SATURDAY NIGHT. THUS,
THE SEVERE RISK APPEARS STILL APPEARS TO BE LOW AT THIS TIME.
FLOODING MAY BE MORE OF A CONCERN ESPECIALLY IF HEAVY RAIN OCCURS
WITH THE MORNING ROUND, FOLLOWED BY ADDITIONAL HEAVY RAIN IN THE
SAME AREAS DURING THE EVENING/OVERNIGHT ROUND GIVEN THE ABUNDANT
DEEP MOISTURE.
THE ENSEMBLE APPROACH OF THE NBM STILL HAS HIGH CHANCES FOR SHOWERS
AND STORMS SUNDAY WITH JUST A GRADUAL LOWERING OF CHANCES AS WE MOVE
THROUGH THE MONDAY THROUGH THURSDAY TIME FRAME. THIS WET PATTERN IS
FAVORED BY MANY OF THE MODELS WHICH HAVE BEEN LEAVING BEHIND A WEAK
UPPER LOW AS THE MAIN TROUGH EXITS. THIS UPPER LOW THEN MEANDERS
SLOWLY AND EVENTUALLY FILLS OVER THE REGION. HOWEVER, IT SHOULD BE
NOTED THAT THE MODELS TYPICALLY STRUGGLE WITH THE LOCATION OF THESE
TYPES OF WEAK CUTOFF LOWS SEVERAL DAYS OUT. A SOMEWHAT DRIER
SCENARIO IS FAVORED BY SOME MODELS, WITH THE CUTOFF UPPER LOW
LOCATED FURTHER TO THE NORTH AND/OR NORTHEAST OR THE UPPER TROUGH
CLEANLY EXITING WITH UPPER RIDGE EDGING SLOWLY IN FROM THE WEST. WE
WILL HAVE TO SEE WHICH SCENARIO PLAYS OUT, BUT FOR NOW THE FORECAST
WILL BE LOW CONFIDENCE BUT STILL FOLLOWING THE WETTER NBM FOR NEXT
WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 118 AM EDT FRI JUL 31 2026
SOME PATCHY FOG IS POSSIBLE AT TRI IN THE EARLY MORNING HOURS BUT
CONFIDENCE IS LOW. OTHERWISE, VFR CONDITIONS ARE EXPECTED. LIGHT
WINDS WILL BECOME MORE SOUTHERLY LATE IN THE PERIOD.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 90 70 85 71 / 0 50 90 90
KNOXVILLE MCGHEE TYSON AIRPORT, TN 89 67 86 71 / 0 30 60 80
OAK RIDGE, TN 87 67 84 70 / 0 30 70 90
TRI CITIES AIRPORT, TN 84 63 85 68 / 0 0 30 70
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...99
AVIATION...99
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