141
FXUS64 KMRX 171755 AAA
AFDMRX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MORRISTOWN TN
155 PM EDT THU JUL 17 2025
..NEW SHORT TERM, LONG TERM, AVIATION
SHORT TERM
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 153 PM EDT THU JUL 17 2025
KEY MESSAGES:
1. SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE EXPECTED EACH
AFTERNOON AND EVENING, WITH THE GREATEST COVERAGE NORTH OF I-40.
2. HEAVY RAIN LEADING TO ISOLATED FLASH FLOODING WILL BE THE PRIMARY
CONCERN WITH STORMS THIS EVENING THROUGH SATURDAY EVENING.
3. HOT AND HUMID CONDITIONS WILL CONTINUE WITH HIGHS RISING INTO THE
90S AND HEAT INDEX VALUES AROUND 100 DEGREES FOR MANY VALLEY
LOCATIONS.
DISCUSSION:
THE PRIMARY SYNOPTIC FEATURE OVER THE REGION THROUGH SATURDAY WILL
BE A LARGE HIGH PRESSURE RIDGE IN THE MID AND UPPER LEVELS, CENTERED
OFF THE EAST COAST OF FL. THIS HIGH WILL DRIFT WESTWARD AND BE
LOCATED JUST OFF THE FL GULF COAST BY SATURDAY EVENING. THE BOTTOM
LINE FOR OUR WEATHER WITH THIS PATTERN IS THAT WE WILL HAVE VERY
LITTLE CHANGE TO THE CURRENT AIR MASS AND EXPECTED WEATHER -
PERSISTENCE APPEARS TO BE A GOOD FORECAST TO FOLLOW. PW VALUES WILL
REMAIN VERY HIGHS, IN THE 1.8 TO 2.1 INCH RANGE. TALL, SKINNY CAPE
PROFILES IN FORECAST SOUNDINGS INDICATE EFFICIENT WARM CLOUD
PROCESSES WILL BE IN PLACE TO PRODUCE HEAVY RAINFALL RATES WITH ANY
THUNDERSTORMS THAT FORM. WE WILL ALSO SEE SOME WEAK MIDLEVEL VORT
MAXES CROSSING EASTERN KY, SW VA, AND SOUTHERN WV, ENHANCING LIFT
FOR STORM DEVELOPMENT IN OUR NORTHERN SECTIONS. LOCALIZED HEAVY RAIN
RATES AND LOW FFG FROM RECENT RAINFALL WILL LIKELY LEAD TO FLOODING
ISSUES EACH AFTERNOON AND EVENING IN SW VA AND NE TN. THE CURRENT
FLOOD WATCH WILL BE MAINTAINED WITH NO CHANGES. A NEW FLOOD WATCH
MAY NEED TO BE ISSUED FOR TOMORROW (AND SATURDAY), BUT WILL HOLD OFF
ON EXTENDING THE CURRENT WATCH AND LET THE MID SHIFT EVALUATE THE
EXTEND OF HEAVY RAINFALL THIS AFTERNOON/EVENING, WHICH WILL AFFECT
THE RISK OF FLOODING TOMORROW. THERE WILL BE A LOW-END RISK OF
DAMAGING WINDS WITH A FEW THUNDERSTORMS TOMORROW AS WELL, WITH
MLCAPE VALUES AROUND 2000 J/KG AGAIN.
THE HEAT INDEX HAS BEEN IN THE 95-100 RANGE SO FAR THIS AFTERNOON,
AND THAT WILL CONTINUE FRIDAY AND SATURDAY WITH SIMILAR
TEMP/DEWPOINTS EXPECTED BOTH DAYS.
LONG TERM
(SATURDAY NIGHT THROUGH NEXT THURSDAY)
ISSUED AT 153 PM EDT THU JUL 17 2025
KEY MESSAGES:
1. SCATTERED STORMS WILL CONTINUE THROUGH MUCH OF THE EXTENDED
PERIOD WITH A LOW CHANCE OF STRONG WIND GUSTS AND LOCALIZED FLOODING
WITH THE STORMS.
2. HOT AND HUMID CONDITIONS PERSIST THROUGH THE PERIOD WITH HEAT
INDEX VALUES OF 100-105 DEGREES ACROSS THE VALLEY NEXT WEEK.
THE HIGH PRESSURE RIDGE WILL CONTINUE TO DRIFT WESWARD ACROSS THE
GULF REGION NEXT WEEK, WITH A BIT MORE AMPLIFICATION ACROSS THE
EASTERN CONUS AS A TROUGH DEEPENS OFF THE EAST COAST IN THE WESTERN
ATLANTIC. THE SLIGHT CHANGE IN PATTERN WILL BRING A MORE NW FLOW
THROUGH THE MID AND UPPER LEVELS, AND WILL PUSH A SURFACE FRONT
TOWARD OUR AREA ON MONDAY. WITH THE NW FLOW, WE WILL SEE A SLIGHT
DROP OF PW VALUES INTO THE 1.6-1.8 RANGE. HOWEVER, LOW LEVELS REMAIN
QUITE MOIST AND UNSTABLE, AND AFTERNOON INSTABILITY WILL CONTINUE TO
SUPPORT SCATTERED STORMS WITH SOME LOW-END POTENTIAL FOR DAMAGING
WIND GUSTS. WITH REDUCED MOISTURE THROUGH THE COLUMN, SHOWER
COVERAGE WILL TREND DOWNWARD THROUGH THE WEEK, BUT THE DRIER AND
SLIGHTLY COOLER AIR ALOFT COULD INCREASE THE POTENTIAL FOR SEVERE
STORMS. THIS IS ALSO A PATTERN THAT FAVORS UPSTREAM MCS REMNANTS TO
TRACK TOWARD OUR AREA, BUT THIS LEVEL OF DETAIL REMAINS UNCERTAIN AT
THIS TIME. INCREASING HEIGHTS ALOFT WILL BRING WARMER TEMPERATURES,
MAINLY TUESDAY ONWARD, WITH THE HEAT INDEX REACHING OVER 100 IN
PARTS OF THE TN VALLEY.
AVIATION
(18Z TAFS) ISSUED AT 153 PM EDT THU JUL 17 2025
SHOWERS AND THUNDERSTORMS ARE LIKELY TO AFFECT TRI THIS AFTERNOON,
AND WILL MENTION VCTS WITH A TEMPO FOR MVFR CONDITIONS AND TS. WITH
THIS EXPECTED RAIN, FOG WILL LIKELY FORM AT TRI LATE TONIGHT, BUT
CONFDIENCE IS LOW ON HOW FAR VIS WILL DROP. EXPECT SIMILAR WEATHER
TOMORROW, WITH SCATTERED TO NUMEROUS AFTERNOON SHOWERS/STORMS, WITH
TRI BEING THE MOST LIKELY LOCATION TO SEE SHOWERS/STORMS AGAIN.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 74 93 75 93 / 20 50 20 60
KNOXVILLE MCGHEE TYSON AIRPORT, TN 74 91 74 89 / 30 60 30 70
OAK RIDGE, TN 73 90 72 88 / 30 60 40 80
TRI CITIES AIRPORT, TN 70 87 70 84 / 40 80 40 80
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR CAMPBELL-CLAIBORNE-
HANCOCK-HAWKINS-JOHNSON-NORTHWEST CARTER-SCOTT TN-SULLIVAN.
VA...FLOOD WATCH UNTIL MIDNIGHT EDT TONIGHT FOR LEE-RUSSELL-SCOTT VA-
WASHINGTON VA-WISE.
SHORT TERM...DGS
LONG TERM....DGS
AVIATION...DGS
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