334
FXUS64 KMRX 201833
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
233 PM EDT MON JUL 20 2026
..NEW DISCUSSION
KEY MESSAGES
UPDATED AT 232 PM EDT MON JUL 20 2026
- ISOLATED SHOWERS AND STORMS THROUGH THIS EVENING. A FEW STRONG
TO MARGINALLY SEVERE STORMS ARE POSSIBLE, SOME OF WHICH COULD
PRODUCE GUSTY WINDS AND LOCALIZED FLOODING.
- COLD FRONTAL PASSAGE TOMORROW INTO WEDNESDAY MAY BRING SEVERAL
ROUNDS OF SHOWERS AND STORMS, WITH A WIDE RANGE OF POTENTIAL
HAZARD OUTCOMES. SEE DISCUSSION BELOW.
- BELOW NORMAL TEMPERATURES AND DRIER AIR WILL FOLLOW BEYOND
WEDNESDAY. PRECIPITATION RETURNS NEXT WEEKEND.
DISCUSSION
ISSUED AT 232 PM EDT MON JUL 20 2026
ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED THROUGH THIS
EVENING. A FEW STORMS COULD BE STRONG TO MARGINALLY SEVERE. THE MAIN
IMPACTS WITH ANY STRONGER STORMS WILL BE GUSTY WINDS TO 40 MPH AND
AN ISOLATED FLOODING POTENTIAL.
THE BULK OF THIS DISCUSSION WILL FOCUS ON THE TUESDAY THROUGH
WEDNESDAY TIMEFRAME. THERE IS A HIGH LEVEL OF UNCERTAINTY REGARDING
THE TIMING AND POTENTIAL IMPACTS DURING THIS TIMEFRAME AS THERE ARE
VARIOUS MODEL SOLUTIONS. GENERALLY THOUGH, WE ARE LOOKING AT THE
POSSIBILITY OF SEVERAL ROUNDS OF SHOWERS AND STORMS WITH THE
POTENTIAL OF STRONG TO SEVERE STORMS FROM TUESDAY MORNING THROUGH
WENDESDAY MORNING.
TUESDAY MORNING:
WE HAVE AN UPPER LEVEL TROUGH AND ADVANCING COLD FRONT COMING IN
FROM THE OHIO RIVER VALLEY. TO OUR SOUTHEAST WE HAVE HIGH PRESSURE
OUT IN THE ATLANTIC AND TO OUR SOUTH A TROPICAL DISTURBANCE ALONG
THE GULF COAST. MOST MODELS KEEP US DRY DURING THE EARLY PORTION OF
THE DAY BUT THE 06Z AND 12Z RUN OF THE HRRR ARE INSISTENT ON FIRING
CONVECTION ACROSS NORTHEAST TN AND SOUTHWEST VA TUESDAY MORNING. IF
CONVECTION FIRES, IT WILL DO SO WITHIN AN ENVIRONMENT THAT IS
SUPPORTIVE OF A FEW STRONG TO SEVERE STORMS. THE MAIN THREATS WILL
BE ISOLATED DAMAGING WIND GUSTS AND FLOODING. THE PROBABILITY OF
THIS SCENARIO IS LOW AS MOST MODELS DO NOT SHOW THIS.
TUESDAY AFTERNOON/LATE EVENING:
MODELS GENERALLY AGREE THAT A SEMI-ORGANIZED TO BROKEN LINE OF
CONVECTION WILL BE APPROACHING OUR NORTHERN AREAS (NORTHERN
CUMBERLAND PLATEAU, NORTHEAST TN, SOUTHWEST VA) FROM OUT OF KY. THIS
COULD BE IN THE FORM OF ONE OR MULTIPLE LINES. AHEAD OF THIS LINE,
WE MAY ALSO SEE A FEW ISOLATED STORMS POP UP ACROSS THE HIGHER
ELEVATIONS OF THE EAST TN MOUNTAINS, WHICH A FEW OF COULD BE STRONG
TO SEVERE. THE BIG QUESTION FOR THE ACTIVITY OUT OF KY IS FAR SOUTH
DOES IT PROGRESS BEFORE IT FALLS APART AND LOSES ITS PUNCH. SOME
MODELS HAVE THE LINE GREATLY DIMINISHING AND SOME SHOW A MORE
ORGANIZED AND STRONGER LINE OF CONVECTION MOVING DOWN INTO OUR AREA.
THE BEST CASE SCENARIO DURING THIS TIMEFRAME IS THAT CONVECTION IS
WEAKENING AS IT MOVES INTO OUR AREA AND WE ONLY SEE A FEW STRONG
STORMS WITH A LOW END THREAT FOR SOME ISOLATED DAMAGING WINDS AND
FLOODING. WORST CASE SCENARIO, THE LINE HOLDS TOGETHER AND STRONG TO
SEVERE STORMS AFFECT A GOOD PORTION OF THE AREA WITH SEVERAL REPORTS
OF DAMAGING WINDS, FLOODING, AND AN ISOLATED TORNADO.
LATE TUESDAY NIGHT/WEDNESDAY MORNING:
THE WEATHER DURING THIS TIMEFRAME LARGELY DEPENDS ON HOW THE EARLIER
CONVECTION EVOLVES AND MOVES THROUGH THE AREA. THERE IS A CONCERNING
TREND THAT I WANT TO DISCUSS THOUGH. THE RRFS AND NAM BOTH GENERALLY
SHOW THE AFTERNOON/EARLY EVENING CONVECTION MOSTLY DISSIPATING
BEFORE IT ENTERS OUR AREA. BOTH OF THESE MODELS THEN SHOW A NEW LINE
OF CONVECTION FIRING ALONG THE REMNANT OUTFLOW BOUNDARY FROM THE
EARLIER STORMS. THIS NEW LINE OF CONVECTION THEN SLOWLY SAGS SOUTH
INTO OUR AREA DURING THE OVERNIGHT HOURS AND REMAINS INTO WEDNESDAY
MORNING, POSSIBLY BECOMING STATIONARY. THIS SCENARIO WOULD LIKELY BE
DUE TO A SLOWER FRONTAL PROGRESSION THROUGH THE AREA, WHICH WOULD BE
DUE TO HIGH PRESSURE IN THE ATLANTIC AND THE TROPICAL DEPRESSION TO
OUR SOUTH (NO WHERE FOR THE FRONT TO GO). THIS WOULD BE A WORST CASE
SCENARIO AS IT WOULD LEAD TO THE TRAINING OF SHOWERS AND STORMS AND
HEAVY RAINFALL OVER THE COURSE OF SEVERAL HOURS, WHICH WOULD LIKELY
LEAD TO SOME SIGNIFICANT FLOODING. AGAIN, THIS IS WORST CASE
SCENARIO. THE MORE LIKELY SCENARIO IS THAT A LINE OF SHOWERS AND
STORMS HAVE ENOUGH PUSH BEHIND THEM, FROM THE FRONT, THAT THEY MOVE
SOUTH AT A DECENT PROGRESSION. EVEN WITH THIS SCENARIO THOUGH,
ISOLATED FLOODING IS STILL POSSIBLE DUE TO RECENT RAIN AND FLOODING
ACROSS THE AREA.
BOTTOM LINE, THIS IS A HIGHLY UNCERTAIN FORECAST IN TERMS OF SYSTEM
EVOLUTION AND THE RESULTANT HAZARDS AND THEIR SEVERITY. PLEASE BE
PREPARED FOR SEVERE WEATHER ANYTIME BETWEEN TUESDAY AND WEDNESDAY
MORNING AND DON'T GET CAUGHT OFF GUARD.
FOLLOWING THE MID-WEEK COLD FRONT, THURSDAY WILL BE VERY NICE WITH
LOW TO MID 80S HIGHS AND DEW POINTS IN THE 60S UNDER HIGH PRESSURE.
TEMPERATURES RISE A COUPLE OF DEGREES INTO THE WEEKEND, BUT FOR THE
MOST PART REMAIN BELOW NORMAL. A SHORTWAVE CYCLING THE TOP OF THE
UPPER RIDGE FRIDAY INTO SATURDAY, MAY BRING PRECIPITATION CHANCES
BACK TO THE AREA AND UNFORTUNATELY INCREASED DEW POINTS YET AGAIN. A
POSSIBLE BOUNDARY THAT COULD GET HUNG UP TO OUR SOUTH MAY COMPLICATE
THINGS.
AVIATION
(18Z TAFS)
ISSUED AT 138 PM EDT MON JUL 20 2026
ISOLATED SHOWERS AND STORMS EXPECTED THROUGH THIS EVENING. LEFT
PROB30S IN AT ALL SITES FOR POSSIBLE CONVECTION BUT THIS MAY BE
TOO AGGRESSIVE GIVEN THE ISOLATED NATURE OF THE CONVECTION. TRI
IS CURRENTLY MVFR AT BKN025 BUT THEY COULD SCATTERED OUT HERE IN
THE NEXT FEW HOURS. FOG IS POSSIBLE AGAIN AT TRI OVERNIGHT DUE TO
YESTERDAY'S RAINFALL BUT LOW CONFIDENCE. WINDS BEGIN TO PICKUP AND
BECOME GUSTY AT TYS AND TRI TOWARD THE END OF THE PERIOD WITH
GUSTS TO AROUND 20KTS OUT OF THE SOUTHWEST.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 75 93 76 90 / 10 10 40 70
KNOXVILLE MCGHEE TYSON AIRPORT, TN 74 90 74 86 / 10 10 80 80
OAK RIDGE, TN 73 90 73 86 / 20 20 90 70
TRI CITIES AIRPORT, TN 69 87 69 83 / 60 50 90 80
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...99
AVIATION...99
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