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

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FXUS64 KMRX 190733
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
333 AM EDT SUN APR 19 2015

.SHORT TERM (TODAY AND TONIGHT)...
SHOWERS HAVE BEEN BLOSSOMING OVER AL OVER THE PAST HOUR...AND EXPECT
THIS INTENSIFICATION TO CONTINUE AS AN UPPER JET STREAK NOSES INTO
THE SE AND SURFACE CYCLOGENESIS OVER WEST TN STRENGTHENS THE LLJ.
AGEOSTROPHIC CIRCULATIONS ASSOCIATED WITH THIS JET WILL PRODUCE
STRONG FORCING OVER THE AREA FOR MOST OF THE DAY. DOWNSLOPE WINDS OF
40 KTS AT 850 MB MAY DELAY PRECIP IN THE TRI-CITIES AREA UNTIL THE
AFTERNOON...BUT THIS WILL SOON BE OVERCOME BY THE MID/UPPER LEVEL
FORCING. INSTABILITY IS WEAK AT THIS TIME...BUT EMBEDDED
THUNDERSTORMS WITH GUSTY WINDS AND LOCALLY HEAVY RAINFALL WILL BE
POSSIBLE EVERYWHERE DUE TO THE STRONG DYNAMICS ALOFT. THIS MAIN AREA
OF LIFT BEGINS TO EXIT SOUTHERN AND WESTERN SECTIONS BETWEEN 18-
21Z...AND NORTHERN SECTIONS INCLUDING TRI-CITIES BETWEEN 21Z-00Z.
THE NAM INDICATES A DRY WINDOW OF ABOUT 4-6 HOURS BEFORE BRINGING IN
ANOTHER AREA OF CONVECTION...WHICH DEVELOPS OVER MIDDLE TN/NRN AL
LATE IN THE AFTERNOON WITH A PRE-FRONTAL TROUGH. THIS AREA MAY HAVE
THE GREATER POTENTIAL FOR SEVERE STORMS AS INSTABILITY IS MUCH MORE
FAVORABLE...WITH MLCAPES REACHING NEAR 1500 J/KG SOUTH. DEEP LAYER
SHEAR AND BRN VALUES INDICATE SUPERCELLS WITH DAMAGING WINDS AND
LARGE HAIL WILL BE POSSIBLE...AND LOW LCL HEIGHTS SUGGEST SOME
TORNADO POTENTIAL AS WELL. HOWEVER...THE DISCONNECT FROM THE
STRONGEST DYNAMIC FORCING MAY LIMIT THE SEVERE POTENTIAL. PLUS...THE
GFS DOES NOT SHOW THIS AREA AT ALL...SO THERE IS SOME UNCERTAINTY
WITH IT. AFTER CATEGORICAL POPS TODAY...WILL LOWER POPS BACK TO HIGH
CHANCES TONIGHT.

.LONG TERM (MONDAY THROUGH SUNDAY)...
BY MONDAY MORNING MOST OF THE ISOLATED STORMS THAT FORMED ALONG THE
PRE-FRONTAL TROUGH SHOULD HAVE MOVED OUT OF THE AREA OR WEAKENED
OVERNIGHT. LOOKS LIKE THERE COULD BE A SECOND ROUND OF SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH A LINE OF CONVECTION MOVING OUT OF
ARKANSAS AND MOVING ACROSS TENNESSEE. THIS LINE WILL LIKELY WEAKEN
AS IT MOVES ACROSS TENNESSEE AND HAVE LOST QUITE A BIT OF POWER BY
THE TIME IT MOVES INTO OUR CWA. SURFACE PRESSURE GRADIENT TIGHTENS
CAUSING WINDS TO PICK UP DURING THE DAY ON MONDAY. SHOULD SEE
WIDESPREAD WINDS OF 10 TO 20 MPH WITH SOME HIGHER GUSTS MIXED IN. AT
THIS POINT MODEL FORECASTS AND MODEL GUIDANCE SUGGESTS WINDS STAY
BELOW ADVISORY CRITERIA, BUT WILL CONTINUE TO MONITOR AS THE COLD
FRONT GETS CLOSER.

THERE WILL ALSO BE A SLIGHT CHANCE FOR SOME STORMS MONDAY EVENING
DEPENDING ON WHAT HAPPENS OVERNIGHT SUNDAY NIGHT. AT THIS POINT
THINK THAT THE BEST ENVIRONMENT/LIFT WILL HAVE MOVED OFF TO OUR EAST
LEAVING US TO BE MOSTLY DRY FOR THIS TIME PERIOD. IF SOMETHING
CAUSES THE FRONT/REMNANT THUNDERSTORM ACTIVITY TO SLOW DOWN THEN OUR
ENVIRONMENT WOULD SUPPORT STORMS THAT COULD CAUSE DAMAGING WINDS AND
MAYBE EVEN SEVERE SIZE HAIL. AGAIN, THIS ALL DEPENDS ON THE LOCATION
OF THE FRONT, AND LIKELY THESE STORMS WILL BE OFF TO THE EAST IN THE
CAROLINAS BY MONDAY EVENING.

REGARDLESS OF WHEN THE FRONT FINALLY MOVES THROUGH, DRIER AIR AND
CLEARER SKIES WILL BE USHERED IN BEHIND IT. HIGH TEMPS WILL BE
KNOCKED BACK BY ABOUT 5 - 10 DEGREES WHEN COMPARING MONDAY HIGHS
WITH TUESDAY HIGHS. WE WILL GET A SHORT BREAK DURING THE MIDDLE OF
THE WEEK WITH GENERALLY ZONAL FLOW ALOFT AND WEST/NORTHWESTERLY
WINDS AT THE SURFACE. WEAK SHORT WAVE WILL QUICKLY MOVE ACROSS LATE
WEDNESDAY LEADING TO A CHANCE FOR SOME SHOWERS, WITH BETTER CHANCES
BEING CONFINED TO NORTHEAST TENNESSEE/SOUTHWEST VIRGINIA. COLD FRONT
WILL THEN MEANDER INTO THE AREA AND STALL OUT SOMEWHERE IN THE
VICINITY AT THE END OF THE WORK WEEK. THIS LEADS TO A DECREASE IN
FORECAST CONFIDENCE AS LOCATION OF THIS FRONT WILL DETERMINE WHERE
SHOWERS AND THUNDERSTORMS DEVELOP LEADING INTO THE WEEKEND. MODELS
DEPICT THE FRONT MOVING SOUTH BEFORE ANOTHER SYSTEM MOVES IN
SATURDAY LEADING TO A GOOD PORTION OF NEXT WEEKEND LIKELY BEING WET
AND CLOUDY. MODELS THEN SHOW DRY WEATHER MOVING IN TO START THE
WORKWEEK AT THE END OF THE FORECAST.

&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             75  62  74  49 / 100  50  50  30
KNOXVILLE MCGHEE TYSON AIRPORT, TN  76  61  74  48 / 100  50  50  30
OAK RIDGE, TN                       74  61  72  47 / 100  50  50  30
TRI CITIES AIRPORT, TN              74  55  74  46 / 100  50  70  40

&&

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

$$

DGS/ABM



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