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

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KMRX 040728
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
328 AM EDT WED MAY 4 2016

.SHORT TERM...(TODAY AND TONIGHT)...UPPER LEVEL TROUGH SET TO DIG
FURTHER SOUTH TODAY AND USHER IN COLDER AIR. BRIEF CLEARING LATE
THIS MORNING BEFORE NEXT ROUNDS OF CLOUDS MOVE IN EARLY/MID
AFTERNOON IN ADVANCE OF COLD FRONT. BY 18 TO 21Z PRECIP CHANCES
BEGIN TO INCREASE AS FRONT IS MAKING ITS WAY TOWARD THE AREA.
SOUNDINGS STILL SUGGEST THAT THERE WILL BE A FEW THUNDERSTORMS WITH
LINE OF SHOWERS MOVING IN AS MLCAPE VALUES ARE GENERALLY IN THE 300
TO 400 J/KG RANGE BETWEEN 21Z AND 00Z. FREEZING HEIGHTS WILL LOWER
THROUGH THE AFTERNOON HOURS WHICH WILL ALLOW FOR SMALL HAIL DUE TO
THE COLD AIR ALOFT. FROM 21Z TO 00Z WILL BE WHEN THE HIGHEST PRECIP
CHANCES ARE IN PLACE AS IT COINCIDE WITH THE BEST UPPER LEVEL
DIVERGENCE...MOISTURE...AND INSTABILITY. THE FRONT SHOULD BE
SOMEWHERE ACROSS OUR CWA AROUND THE 00Z TIME-FRAME BUT NOT QUITE ALL
THE WAY THROUGH. PRECIP CHANCES DECREASE WITH FRONTAL PASSAGE.
THUNDERSTORM THREAT DECREASES WITH FRONTAL PASSAGE.

TONIGHT...PROXIMITY TO CENTER OF THE LOW PRESSURE...LINGERING
MOISTURE...COLD AIR ADVECTION...AND NW FLOW WILL CONTINUE RAISED POP
CHANCES ACROSS OUR EASTERN MOUNTAINS...NETN..AND SWVA. BASED ON THE
NAM SOUNDINGS...SNOW BEGINS TO FALL AROUND 6K FEET AT 00Z...5500
FEET AT 03Z...5K FEET AT 06Z...AND 4500 FEET AT 09Z. SNOW FORECAST
IS BASED ON NAM SOUNDINGS AS GFS IS QUITE DIFFERENT WITH THE
MOISTURE DEPTH. IF THE GFS PANS OUT THERE WOULD BE NO SNOW DUE TO NO
MOISTURE PRESENT IN THE SNOW GROWTH ZONE. GOING WITH THE NAM DUE TO
ITS ABILITY TO BETTER RESOLVE NW FLOW TERRAIN EVENTS. HAVE AROUND 1
TO 1.5 INCHES OF SNOW IN GRIDS AT ELEVATIONS ABOVE 5000 FEET BY
TOMORROW MORNING. LOCALLY HIGHER AMOUNTS POSSIBLE ON THE HIGHEST
PEAKS. TRACE TO HALF AN INCH POSSIBLE ABOVE 4500 FEET. ANY OUTDOORS
MEN OR AREA HIKERS ARE ADVISED TO USE CAUTION TONIGHT DUE TO
EXPECTED SNOW. ALSO...BREEZY NW WINDS AND UNSEASONABLE COLD
TEMPERATURES WILL GIVE BELOW FREEZING APPARENT TEMPERATURES. APPARENT
TEMPS AROUND 3000 FEET WILL BE NEAR FREEZING...AND DOWN INTO THE LOW
20S ONCE YOU GET ABOVE 4500 FEET. LOWS IN THE VALLEY TONIGHT WILL
RANGE FROM NEAR 40 NORTH TO LOW TO MID 40S SOUTH. THESE TEMPS WILL
BE 5 TO 10 DEGREES BELOW NORMAL. PRECIP CHANCES GRADUALLY DIMINISH
THROUGH THE NIGHT.

.LONG TERM (THURSDAY THROUGH TUESDAY)...FOR THURSDAY AND FRIDAY...
AN UNSEASONABLY COLD AND CLOSED UPPER TROUGH WILL MOVE ACROSS THE
SOUTHERN APPALACHIANS TO THE MID-ATLANTIC STATES. MODELS SHOW A
DEFORMATION ZONE THAT ENHANCES THE FORCING AREAS MAINLY NORTH OF
INTERSTATE 40...BUT NORTHWEST FLOW OROGRAPHIC LIFT ALSO OVER THE
FAR EASTERN TENNESSEE MOUNTAINS/HIGH KNOB AREA.

DUE TO THE COLD AIR ALOFT...A GOOD DEAL OF CONVECTIVE SHOWERS AS
WELL. VERTICAL PROFILE SUPPORTS A MIX/CHANGE OVER TO SNOW ACROSS
THE HIGHEST ELEVATIONS...GENERALLY AT OR ABOVE 4500 FEET. TOTAL
SNOW ACCUMULATIONS OF 2 INCHES ARE POSSIBLE ACROSS THE HIGHEST
PEAKS...SUCH AS MOUNT LECONTE. THIS IS SIGNIFICANT SINCE ANY HIKERS
WILL NOT EXPECT THIS TYPE OF WEATHER FOR EARLY MAY. WILL HIGHLIGHT
IN HWO/SPS AND GRAPHIC PRODUCTS.

FOR SATURDAY...UPPER TROUGH EXITS THE REGION WITH WEAK RIDGING.
NORTHWEST FLOW WILL REMAIN THIS WEEKEND WITH A SERIES OF WEAK
SHORTWAVES PRODUCING CONVECTON FROM THE OHIO VALLEY INTO THE
SOUTHWEST VIRGINIA AND NORTHEAST TENNESSEE FOR SUNDAY AND MONDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             71  47  63  48 /  60  50  20  10
KNOXVILLE MCGHEE TYSON AIRPORT, TN  67  45  58  46 /  70  80  50  30
OAK RIDGE, TN                       67  46  59  47 /  70  80  40  30
TRI CITIES AIRPORT, TN              64  43  56  46 /  50  90  70  60

&&

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

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.