Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000
FXUS64 KMRX 271857
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
257 PM EDT SAT JUN 27 2015

.SHORT TERM /THIS AFTERNOON THROUGH SUNDAY/...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO MOVE ACROSS
THE REGION AHEAD OF A COLD FRONT CURRENTLY DRAPED FROM AROUND
COOKEVILLE TN...SOUTHWEST TO FLORENCE AL. THE FRONT WILL CONTINUE TO
TRACK TOWARD THE REGION THIS AFTERNOON...MAKING INTO PORTIONS OF THE
CUMBERLAND PLATEAU BY 20-21Z...AND THROUGH MUCH OF THE REGION BY 01-
02Z. ALONG/JUST AHEAD OF THE FRONT A LINE OF SEMI ORGANIZED
SHOWERS/THUNDERSTORMS HAVE DEVELOPED AND PROGGED TO TRACK INTO THE
REGION WITH THE FRONT LATE THIS AFTERNOON AND EARLY EVENING. MOSTLY
CLOUDY CONDITIONS HAVE LINGERED THROUGH MOST OF THE DAY...BUT SOME
RECENT BREAKS HAVE ALLOWED FOR SOME HEATING AND MARGINAL INSTABILITY
TO DEVELOP. VALUES AS HIGH AS 1000-1500 J/KG HAVE DEVELOPED BY MID
AFTERNOON...WHICH WOULD CERTAINLY HELP IN MAINTAINING AND EVEN
INTENSIFYING THE CURRENT ACTIVITY. THE SHEAR IS MUCH BETTER THAN
YESTERDAY...WITH UNIDIRECTIONAL BULK SHEAR VALUES AT 40-50 KTS.

THE COMBINATION OF THESE TWO FACTORS HAS LEAD TO THE DEVELOPMENT OF
THE AFOREMENTIONED LINE OF SEMI-ORGANIZED CLUSTERS OF STORMS...WHICH
WILL BE CAPABLE OF BECOMING STRONG TO LOCALLY SEVERE AS THEY MOVE
INTO THIS ENVIRONMENT. OF PARTICULAR CONCERN WILL BE GUSTY DOWNBURST
WINDS GIVEN THE INVERTED-V SOUNDING PROFILES AND THE DRIER AIR
PRESENT AT THE SURFACE. THIS WOULD HELP TO ACCELERATE DOWNDRAFTS AS
THEY APPROACH THE SURFACE...INCREASING THE DOWNBURST THREAT.
ADDITIONALLY...WET BULB ZERO HEIGHTS ARE MUCH LOWER TODAY...AND WITH
COLDER AIR ALOFT PRESENT...A MARGINALLY SEVERE HAIL RISK WILL ALSO
EXIST WITH ANY OF THIS LATE AFTERNOON TO EVENING ACTIVITY AS WELL.

IN WAKE OF THE FRONTAL PASSAGE THIS EVENING...SHOWERS AND
THUNDERSTORMS WILL DECREASE QUICKLY AS DRIER/COOLER AIR MOVES IN.
HOWEVER...THE CLEARING SKY...LIGHTER WINDS AND A NOW MOIST BOUNDARY
LAYER WILL ALLOW FOR PATCHY FOG TO DEVELOP LATE TONIGHT. LOWS
TONIGHT WILL BE MUCH MORE COMFORTABLE...IN THE MID 50S TO LOW 60S.
FOR SUNDAY...THE COOLER WEATHER WILL CONTINUE WITH PREVAILING NW
FLOW. STILL...WITH AMPLE SUNSHINE HIGHS MAY BE A DEGREE OR TWO
WARMER THAN TODAY...IN THE UPPER 70S/LOWER 80S GENERALLY.

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
OVERALL WEATHER PATTERN WILL SEE AN UPPER TROUGH POSITIONED OVER
THE REGION THROUGH THE EXTENDED. EARLY IN THE PERIOD...DRY AND MUCH
COOLER AIR WILL CONTINUE TO PUSH INTO THE AREA SUNDAY NIGHT BEHIND
AN EXITING COLD FRONT. WILL THEN TRANSITION INTO AN UNSETTLE
PATTERN AS A SERIES OF SYSTEMS DROP INTO THE AREA. A SECONDARY
FRONT MOVES IN LATE MONDAY INTO TUESDAY. THIS WILL BRING LOW LEVEL
MOISTURE BACK INTO THE AREA AND PROVIDE A CHANCE OF SHOWERS AND
THUNDERSTORMS. MODELS DIFFER IN TIMING OF FEATURES THROUGH THE REST
OF THE PERIOD BUT OVERALL PATTERN BRINGS IN A SERIES OF SHORT WAVES
THROUGH THE REGION WEDNESDAY THROUGH SATURDAY...PROVIDING A CHANCE
OF SCATTERED CONVECTION EACH DAY. THE STRONGEST OF THESE WAVES WILL
MOVE IN THURSDAY INTO FRIDAY. TEMPERATURES WILL STAY A LITTLE BELOW
NORMAL FOR MUCH OF THE PERIOD WITH READINGS BEGINNING TO WARM A BIT
FRIDAY OR SATURDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             63  85  62  89 /  10   0   0  20
KNOXVILLE MCGHEE TYSON AIRPORT, TN  61  82  60  86 /  20   0  10  20
OAK RIDGE, TN                       60  83  60  86 /  10   0  10  20
TRI CITIES AIRPORT, TN              57  79  56  83 /  40  10  10  20

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

AMP/MJB



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