494
FXUS64 KMRX 140250
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
1050 PM EDT THU MAR 13 2025
..NEW UPDATE
UPDATE
ISSUED AT 1045 PM EDT THU MAR 13 2025
A NEW UPDATE TO REMOVE SHOWERS AND STORMS FROM SOUTHEAST
TENNESSEE. ALSO KEPT A SMALL CHANCE IN WISE COUNTY NEXT HOUR AS A
COMPLEX OF SHOWERS AND STORMS MOVE SOUTHEAST TOWARD THE VIRGINIA
AND WEST VIRGINIA BORDER. ANOTHER COMPLEX MOVING FROM EAST CENTRAL
ALABAMA INTO WESTERN GEORGIA WILL NOT AFFECT EAST TENNESSEE. SKIES
WILL BE CLEARING FOR THE REST OF THE NIGHT. WEAKENING SHORTWAVE
TROUGH IS ABOUT TO MOVE OUT AND INTO THE CAROLINAS AND MID
ATLANTIC STATES WITH MID LEVEL RIDGING MOVING IN THROUGH THE REST
OF TONIGHT AND INTO FRIDAY MORNING. TEMPERATURES COOLING A LITTLE
SLOWER WHERE CLOUDS FORMED WITH THE CONVECTION BUT ALSO DROPPED
WHERE RAIN FELL. UPDATED HOURLY TEMPERATURES AND DEWPOINTS.
UPDATED FORECAST SENT.
UPDATE
ISSUED AT 900 PM EDT THU MAR 13 2025
UPDATED FORECAST AS SHOWERS AND STORMS ARE DECREASING IN COVERAGE
AND INTENSITY. STILL SOME OVER THE SOUTHERN PLATEAU AND SOUTHERN
VALLEY AT 900 PM BUT EXPECT THEM TO DIE DOWN IN AN HOUR. SKIES ARE
PARTLY CLOUDY TO MOSTLY CLOUDY IN AREAS STILL GETTING SHOWERS AND
TEMPERATURES ARE IN THE UPPER 50S TO UPPER 60S. WINDS ARE GENERALLY
LIGHT ACROSS THE REGION. SOME AREAS RECEIVED UP TO ABOUT AN INCH
OR MORE OF MUCH NEEDED RAINFALL IN THE SOUTHERN PART OF THE FORECAST
AREA. MAY SEE SOME FOG IN THE RAIN AREAS BUT DID NOT ADD TO
FORECAST. UPDATE SENT.
SHORT TERM
(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 242 PM EDT THU MAR 13 2025
KEY MESSAGES:
1. WARM TEMPERATURES, DEEP MIXING, AND GUSTY WINDS ON FRIDAY WILL
PROMOTE ELEVATED FIRE DANGER LEVELS.
2. HIGH WINDS RAMP UP ACROSS THE MOUNTAINS FRIDAY NIGHT. GUSTS OF
60-70MPH LIKELY OVERNIGHT, BEFORE EVEN STRONGER WINDS ARRIVE IN
THE LONG TERM.
DISCUSSION:
SOME ISOLATED SHOWERS AND THUNDERSTORMS CONTINUE TO
DEVELOP/PERSIST ACROSS THE REGION THIS AFTERNOON. THIS SEEMS
LARGELY TIED TO COMBINATION OF TERRAIN (CUMBERLAND PLATEAU AND THE
APPALACHIANS) AND THE NORTHWARD ADVANCE OF MID 50S DEWPOINTS.
WILL LEAVE THE WIDESPREAD SLIGHT CHANCE POPS IN THE FORECAST
THROUGH THE AFTERNOON BUT I DON'T EXPECT THERE WILL BE MUCH MORE
COVERAGE THAN WHAT IS CURRENTLY ON RADAR. THAT SAID, MODEL
SOUNDINGS SHOW VERY STEEP LAPSE RATES SO SOME DECENTLY TALL STORMS
CAPABLE OF SMALL HAIL AND GUSTY WINDS IF ANY DEVELOP. THE WINDOW
OF OPPORTUNITY FOR ANY CONVECTION WILL PERSIST THROUGH 03Z OR
THEREABOUTS. AFTERWARDS, DRY CONDITIONS ARE EXPECTED THROUGH
FRIDAY.
BY LATE TONIGHT, THE UPPER LOW/SHORTWAVE RESPONSIBLE FOR THE
ISOLATED SHOWERS ACROSS THE REGION WILL HAVE SHIFTED WELL TO OUR
SOUTHEAST. HEIGHTS WILL THEN RISE AHEAD OF THE SYSTEM THAT WILL
BRING US SEVERE STORMS ON SATURDAY. AS SUCH, TOMORROW SHOULD BE
WARMER THAN EVEN TODAY, WITH MID AND UPPER 70S FORECAST FOR THE TN
VALLEY. WINDS WILL BEGIN TO PICKUP AS WELL ON FRIDAY. MODEL
SOUNDINGS SHOW THAT WE MIX OUT TO NEARLY 7000 FT AGL TOMORROW
AFTERNOON, WHICH WILL TAP INTO SOME 25-30KT FLOW ALOFT AND HELP TO
PROMOTE GUSTY AFTERNOON WINDS. THIS DEEP MIXING IS ALSO GOING TO
LEAD TO LOW AFTERNOON RH VALUES ONCE AGAIN. WILL NEED TO
COORDINATE WITH FIRE WEATHER PARTNERS ON WHETHER ANY HEADLINES
WILL BE NEEDED. I SAY THAT BECAUSE WHILE LOWER ELEVATIONS WON'T BE
NEAR ADVISORY LEVELS DURING THE AFTERNOON TOMORROW, THE WIND FIELD
ALOFT IS GOING TO STRENGTHEN CONSIDERABLY AS WE HEAD INTO THE
EVENING HOURS. TO THAT END, WE'VE GONE AHEAD AND UPGRADED THE HIGH
WIND WATCH TO A WARNING FOR THE MOUNTAIN ZONES. THERE COULD BE
SOME OVERLAP THESE STRONGER WINDS WITH THE LOWER RH VALUES WHICH
WOULD ELEVATE FIRE DANGER LEVELS FOR SURE.
FRIDAY NIGHT, WINDS WILL CONTINUE TO RAMP UP IN THE MOUNTAINS AS
A STRONG H85 WIND FIELD BEGINS TO SPREAD ACROSS THE AREA IN
ADVANCE OF THE SEVERE WEATHER EVENT. PUT GUSTS TO 80MPH IN THE
HIGH WIND WARNING. WHILE THOSE TYPES OF GUSTS SHOULD LARGELY HOLD
OFF UNTIL THE LONG TERM PERIOD, GUSTS OF 60-70MPH WILL CERTAINLY
BE POSSIBLE FRIDAY NIGHT.
LONG TERM
(SATURDAY THROUGH NEXT THURSDAY)
ISSUED AT 242 PM EDT THU MAR 13 2025
KEY MESSAGES:
1. A VERY STRONG AND DYNAMIC SYSTEM WILL IMPACT THE REGION FRIDAY
NIGHT THROUGH EARLY SUNDAY MORNING WITH A HIGH-END, LONG-DURATION
MOUNTAIN WAVE EVENT LIKELY ACROSS THE MOUNTAINS AND FOOTHILLS
THROUGH SATURDAY NIGHT.
2. A SIGNIFICANT SEVERE WEATHER OUTBREAK IS LIKELY ACROSS THE REGION
WITH THE GREATEST THREAT IN OUR AREA BEING ALONG THE CUMBERLAND
PLATEAU THROUGH SOUTHEAST TENNESSEE AND SOUTHWEST NORTH CAROLINA.
THE GREATEST THREAT IS FOR SIGNIFICANT AND WIDESPREAD DAMAGING WINDS
WITH TORNADOES AND LARGE HAIL ALSO POSSIBLE.
3. FLOODING OF URBAN AREAS AND FLOOD PRONE LOCATIONS WILL BE
POSSIBLE DUE TO HEAVY RAINFALL RATES SATURDAY NIGHT.
4. DRIER AND COOLER CONDITIONS ARRIVE SUNDAY NIGHT INTO MONDAY,
FOLLOWED BY A WARMING TREND AND ANOTHER SYSTEM BY WEDNESDAY.
DISCUSSION:
SATURDAY MORNING, WE WILL BE UNDER THE INFLUENCE OF BROAD UPPER-
LEVEL DIFFLUENCE WITH A POTENT SHORTWAVE VORT MAX PREPARING TO EJECT
FROM THE LONGWAVE TROUGH AXIS ACROSS THE ARKLATEX REGION. AN
OCCLUDING SURFACE LOW WILL BE ACROSS THE GREAT LAKES REGION WITH A
TRAILING COLD FRONT ACROSS THE MISSISSIPPI VALLEY. DUE TO AN
INCREASING UPPER-LEVEL JET DIVERGENCE, A SUBTLE SURFACE LOW FEATURE
WILL DEVELOP ALONG THIS COLD FRONT ACROSS THE LOWER MISSISSIPPI
VALLEY AND RACE NORTHEASTWARD SATURDAY AFTERNOON AND NIGHT. THIS
WILL BRING AN INCREASING RISK OF A DANGEROUS SIGNIFICANT SEVERE
WEATHER OUTBREAK FOR PORTIONS OF THE MID-SOUTH AND TENNESSEE VALLEY
ACROSS MISSISSIPPI, ALABAMA, AND TENNESSEE. SUPERCELL THUNDERSTORM
STRUCTURES CAPABLE OF LARGE, LONG-TRACK TORNADOES WILL BE POSSIBLE
AS WELL AS QLCS CONVECTION DURING THE EVENING AND OVERNIGHT HOURS
WITH A CONTINUED HIGH-END DAMAGING WIND RISK AND A CONTINUED RISK OF
TORNADOES. BEHIND THE FRONT, COOLER AND DRIER WEATHER ARRIVE EARLY
TO MID NEXT WEEK. THE FOLLOWING SECTIONS ARE GROUPED BASED ON ORDER
OF OCCURRENCE AND WITH RESPECT TO OUR AREA:
1. MOUNTAIN WAVES/FIRE WEATHER
A STRENGTHENING PRESSURE GRADIENT AND INCREASING 850MB LLJ OVER 50
KT WILL RESULT IN MOUNTAIN WAVE HIGH WINDS INCREASING INTO SATURDAY
MORNING AND DURING THE DAY. THE LLJ WILL INCREASE TO OVER 70 KT BY
SATURDAY EVENING WITH INTENSE HIGH-END MOUNTAIN WAVE HIGH WINDS
EXPECTED. BASED ON EXTENT OF WINDS AND DRY CONDITIONS SEEN IN RECENT
DAYS, FIRE WEATHER IS OF SIGNIFICANT CONCERN, ESPECIALLY IN THE
MOUNTAINS AND FOOTHILLS. THE HIGH WIND WATCH WILL BE UPGRADED TO A
HIGH WIND WARNING SINCE WE ARE NOW WITHIN 24 TO 36 HOURS OF THE HIGH
WINDS BEGINNING AND CONFIDENCE CONTINUES TO INCREASE IN THESE
INTENSE WINDS FOR THE MOUNTAINS AND FOOTHILLS.
2. SEVERE WEATHER
AS MENTIONED ABOVE, A NEW SUBTLE SURFACE LOW WILL BE DEVELOPING
BENEATH A REGION OF UPPER-LEVEL DIVERGENCE ACROSS THE LOWER
MISSISSIPPI VALLEY ON SATURDAY MORNING. THIS LOW WILL MOVE RAPIDLY
NORTHEAST SATURDAY AFTERNOON AND EVENING WITH THE COLD FRONT MOVING
EASTWARD. WITH A STRONG SSW 850MB LLJ AROUND 70+ KT AND UPPER-LEVEL
500MB WINDS FROM THE WSW AT 80+ KT BY SATURDAY EVENING, EFFECTIVE
BULK SHEAR WILL BE VERY STRONG ACROSS THE MID-SOUTH AND TENNESSEE
VALLEY. 15Z RAP FORECAST SOUNDINGS AT CHA FOR 18Z SATURDAY ARE
SHOWING LOW INSTABILITY AND VERY HIGH SHEAR VALUES. MLCAPE AROUND
500 J/KG WITH EBSHEAR AROUND 55 KT. ESRH BETWEEN 300 TO 500 M2/S2 IS
VERY HIGH, AND THE STRONG LOW-LEVEL SHEAR IS RESULTING IN LONG,
CURVED HODOGRAPHS FAVORABLE TO TORNADOES, INCLUDING STRONG AND LONG-
TRACK TORNADOES. THE BIG LIMITATION FOR SATURDAY'S SEVERE CONVECTION
ACROSS OUR REGION MAY BE MORNING SHOWERS AND THUNDERSTORMS THAT
STABILIZE PORTIONS OF THE FORECAST AREA. THIS COULD STABILIZE THE
BOUNDARY LAYER AND LIMIT SURFACE BASED CONVECTION. HOWEVER, IT STILL
APPEARS LIKELY THAT STRONG SOUTHERLY FLOW WILL LIFT THIS NORTHWARD,
AND AT THE VERY LEAST, DESTABILIZE THE SOUTHERN PLATEAU AND SOUTHERN
VALLEY ENOUGH TO SUPPORT HIGH-END SEVERE WEATHER. FOR THIS REASON,
THE HIGHEST RISK OF SEVERE WEATHER ACROSS OUR FORECAST AREA WILL BE
COUNTIES ALONG THE SOUTHERN CUMBERLAND PLATEAU AND SOUTHEAST
TENNESSEE.
ON SATURDAY AFTERNOON, IT IS LIKELY THAT SUPERCELLS DEVELOP ALONG
THE COLD FRONT OR PREFRONTAL TROUGH ACROSS NORTHEAST AND EAST-
CENTRAL MISSISSIPPI AND CENTRAL AND NORTHERN ALABAMA; THESE WOULD
BEGIN TO TRACK NORTHEAST THROUGH THE EVENING. THESE STORMS WOULD
MOST LIKELY ARRIVE IN SOUTHEAST TENNESSEE SOMETIME BETWEEN 23Z AND
04Z SATURDAY EVENING WITH A GRADUAL UPSCALE GROWTH INTO A QLCS WITH
EMBEDDED CIRCULATIONS AS THE NIGHT PROGRESSES. STORM MOTION WILL BE
VERY FAST, AROUND 220/65KT. THE FAST MOVEMENT AND KINEMATIC WIND
PROFILE WILL SUPPORT SEVERE THUNDERSTORM DAMAGING WINDS AREA-WIDE.
THE MAIN TORNADO RISK, INCLUDING THE MOST PROBABLE SIGNIFICANT, LONG-
TRACK TORNADO RISK, IS LIKELY TO REMAIN SOUTH AND WEST OF THE
KNOXVILLE AREA WHERE BETTER BOUNDARY LAYER MOISTURE IS PRESENT, BUT
THERE WILL AT LEAST BE A LOW RISK OF TORNADOES AREA-WIDE. THERE WILL
BE A RISK OF LARGE HAIL WITH SUPERCELL THUNDERSTORMS, BUT THE
OVERALL HAIL RISK IS LOW TO MEDIUM.
3. FLOODING
AHEAD OF THE APPROACHING COLD FRONT, VERY STRONG 850MB MOISTURE
TRANSPORT MOVES INTO OUR AREA WITH PWATS REACHING TO NEAR RECORD
HIGH VALUES OF 1.4 TO 1.5 INCHES. THIS IS AROUND 3.5 SIGMA ABOVE
NORMAL VALUES WHICH WILL SUPPORT HEAVY RAIN RATES. DUE TO HEAVY RAIN
RATES, FLOODING OF URBAN AREAS AND FLOOD PRONE LOCATIONS IS EXPECTED.
SUNDAY THROUGH WEDNESDAY
UPSLOPE FLOW KEEPS CLOUDS AND SHOWERS ACROSS THE MOUNTAINS ON SUNDAY
WITH A CHANCE OF SOME LIGHT SNOW OR RIME ICE ON SUNDAY NIGHT BEFORE
DRY AIR AND CLEAR SKY CONDITIONS RETURN ON MONDAY. WITH TROUGHING
EARLY WEEK, TEMPERATURES WILL BE COOLER EARLY IN THE WEEK BEFORE
RIDGING BRINGS A RETURN TO ABOVE NORMAL TEMPERATURES BY MID-WEEK.
AVIATION
(00Z TAFS)
ISSUED AT 730 PM EDT THU MAR 13 2025
A POSSIBLE THUNDERSTORM NEAR TYS AND POSSIBLY CHA NEXT HOUR BEFORE
DISSIPATING SO VCTS REMARKS. VFR FLIGHT CATEGORIES HOWEVER WILL
CONTINUE THROUGH THE 00Z TAF PERIOD. WINDS WILL BE LIGHT THROUGH
ABOUT 18Z FRIDAY, AFTER WHICH POINT THE POTENTIAL FOR GUSTS UP TO
ABOUT 20 KNOTS BEGINS TO INCREASE.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 52 76 61 73 / 10 10 50 90
KNOXVILLE MCGHEE TYSON AIRPORT, TN 48 78 60 73 / 30 0 30 80
OAK RIDGE, TN 48 77 59 72 / 30 0 30 80
TRI CITIES AIRPORT, TN 45 75 54 74 / 10 0 10 50
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...HIGH WIND WARNING FROM 8 PM FRIDAY TO 2 AM EDT SUNDAY FOR BLOUNT
SMOKY MOUNTAINS-COCKE SMOKY MOUNTAINS-EAST POLK-JOHNSON-
SEVIER SMOKY MOUNTAINS-SOUTHEAST CARTER-SOUTHEAST GREENE-
SOUTHEAST MONROE-UNICOI.
VA...NONE.
SHORT TERM...TD
LONG TERM....JB
AVIATION...TD
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