FXUS64 KMRX 090143
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
830 PM EST TUE DEC 8 2009
.DISCUSSION...FORECAST ON TRACK. 00Z SOUNDINGS AND AREA VWP'S
INDICATE EXPECTED STRONG LOW LEVEL JET. PRESENT SE SURFACE WINDS
WITH H85 SPEED MAX TO THE WEST PRESENT GOOD DOWNSLOPING WIND
CONDITIONS ALONG FOOTHILLS. ELEVATED WARM FRONT HAS BROUGHT
WIDESPREAD MODERATE RAINFALL NE THROUGH THE AREA THIS EVENING.
SLIGHT CHANCE FOR SEVERE TSTMS EXTENDED NE TO INCLUDE CHA AND VCNTY
OVERNIGHT. MAIN THREAT IS DAMAGING WINDS. NORTH OF THIS AREA
ELEVATED CONVECTION COULD PRODUCE STRONG WINDS AT THE SURFACE. WINDS
WILL CONTINUE TO INCREASE ACROSS THE AREA OVERNIGHT. SON
PREVIOUS DISCUSSION:
SHORT TERM...(TONIGHT AND WEDNESDAY)...STRONG DYNAMIC SYSTEM WILL
MOVE OUT OF THE SOUTHERN PLAINS TOWARD THE WESTERN GREAT LAKES
TONIGHT AND WEDNESDAY. TROPOPAUSE FOLD REMAINS EVIDENT OVER THE
PLAINS STATES WHICH WILL PRODUCE STRONG CYCLOGENESIS FROM THE
SOUTHERN PLAINS TO THE WESTERN GREAT LAKES. TIGHTENING PRESSURE
GRADIENTS AROUND THIS INTENSIFYING SURFACE LOW WILL PRODUCE A STRONG
SOUTHERLY JET (850MB WINDS OF 80KTS BY TUESDAY NIGHT).
THE MAIN CONCERN IS THE STRONG WINDS JUST OFF THE SURFACE. DAMAGING
HIGH WINDS ARE LIKELY ACROSS THE HIGHER ELEVATIONS OVERNIGHT THROUGH
WEDNESDAY. AS THE COLD FRONT MOVES ACROSS THE AREA LATE TONIGHT...
ELEVATED INSTABILITY WILL ALLOW A LINE OF STORMS TO MOVE ACROSS THE
FORECAST. THE STORMS WILL LIKELY TAP INTO THE 850MB JET OF 80KTS
WITH THE POTENTIAL OF DAMAGING WINDS ALONG THIS SQUALL. WILL
HIGHLIGHT THIS THREAT IN THE HWO WITH THE POTENTIAL OF WIDESPREAD
TREES AND POWER LINES BEING BLOWN DOWN.
FOR WEDNESDAY...STRONG GRADIENT WINDS WILL CONTINUE. LAPSE RATES
BECOME FAIRLY STEEP AS SUNSHINE RETURNS ALLOWING FOR STRONG
LOW-LEVEL JET TO BE FELT AREA-WIDE.
HAVE GENERALLY FOLLOWED GFS NUMBERS. TEMPERATURES TONIGHT WILL
LIKELY SLOW RISE DURING THE NIGHT.
LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)... AIRMASS DRIES OUT
WEDNESDAY NIGHT INTO THURSDAY...ALTHO I DID HANG ON TO CLOUDS AND
SOME SNOW SHOWERS OR FLURRIES FOR MY NRN MOST AREAS. MAY ACTUALLY
SEE SOME SUNSHINE ON THURSDAY WITH DRY WEATHER LASTING INTO FRIDAY
...AS WE SEE A ZONAL FLOW ALOFT AND BRIEF SURFACE RIDGE OVER THE
REGION.
OTHERWISE...TWO MAIN SYSTEMS WILL AFFECT THE REGION DURING THESE
PERIODS...BRINGING CHANCES OF MOSTLY LIQUID PRECIPITATION (PCPN).
THE FIRST WILL BE A WEAK SHORT WAVE THAT LOOKS TO DEVELOP SOME
ISENTROPIC LIFT OVER THE TN VALLEY AND SRN APPALACHIANS VERY LATE
FRIDAY NIGHT INTO SATURDAY. 12Z MODELS SEEM IN BETTER AGREEMENT ON
THE BULK OF THIS PCPN ARRIVING AFTER 12Z SATURDAY...AND WE MAY NEED
TO CONTINUE TO INCREASE POPS ACCORDINGLY FOR SATURDAY. HOWEVER...
THIS IS A WEAK SHORTWAVE AND WOULD PREFER TO WAIT AND SEE. PCPN TYPE
LOOKS TO BE MOSTLY RAIN AS LOW LEVEL WARM AIR ADVECTION KICKS IN
RATHER ROBUSTLY BY THE LATE MORNING AND EARLY AFTERNOON HOURS. I
CONTINUED RAIN OR SNOW WORDING FOR NOW...BASED ON A LOOK AT FORECAST
SOUNDINGS ACROSS THE REGION FOR THAT PERIOD. AIRMASS WILL MODIFY
SOME AFTER THE CHILL IT TAKES ON FOLLOWING THE DEPARTURE OF OUR
STRONG WEDNESDAY SYSTEM...SO A TRANSITION TO RAIN BY EARLY SATURDAY
AFTERNOON EVEN ACROSS SW VA AND NE TN SEEMS REASONABLE.
SECOND SYSTEM IS BEING ADVERTISED AS MUCH STRONGER...WITH A
DEEPENING UPPER LEVEL TROUGH APPROACHING MONDAY NIGHT INTO TUESDAY.
THIS SYSTEM WILL BRING A SURFACE LOW AND MUCH MORE GULF MOISTURE
NORTHWARD...WITH WARM AIR ADVECTION/ISENTROPIC LIFT BRINGING MAINLY
A RAIN EVENT. UNSURE ON TIMING...SO KEPT THE USUAL RAIN OR SNOW PCPN
TYPE FOR TUESDAY NIGHT. THE ASSOCIATED LOW LEVEL JET SHOULD NOT BE
AS STRONG AS RECENT ONES...PROBABLY AROUND 25 TO 40 KNOTS.
TEMPS WERE ADJUSTED IN LINE WITH LATEST 12Z GFSX MOS...WHICH WAS
FAIRLY CLOSE TO 00Z GFSX NUMBERS. SOME CONFIDENCE OVERALL WITH THE
FORECAST AS GFS AND ECMWF SEEMED SIMILAR WITH MAIN FEATURES AND
TIMING.
&&
.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN 47 59 29 45 24 / 100 10 10 10 10
KNOXVILLE MCGHEE TYSON AIRPORT, TN 43 54 25 40 18 / 100 10 10 10 10
OAK RIDGE, TN 43 57 26 39 17 / 100 10 10 10 10
TRI CITIES AIRPORT, TN 41 57 24 37 15 / 100 20 10 10 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR THE FOLLOWING
ZONES: CHEROKEE...CLAY.
TN...HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR THE FOLLOWING
ZONES: BLOUNT SMOKY MOUNTAINS...COCKE SMOKY MOUNTAINS...
EAST POLK...JOHNSON...MCMINN...NW BLOUNT...NORTH SEVIER...
NORTHWEST CARTER...NORTHWEST COCKE...NORTHWEST GREENE...
NORTHWEST MONROE...SEVIER SMOKY MOUNTAINS...SOUTHEAST
CARTER...SOUTHEAST GREENE...SOUTHEAST MONROE...SULLIVAN...
UNICOI...WASHINGTON TN...WEST POLK.
WIND ADVISORY FROM 1 AM TO 7 PM EST WEDNESDAY FOR THE FOLLOWING
ZONES: ANDERSON...BRADLEY...GRAINGER...HAMBLEN...HAMILTON...
HANCOCK...HAWKINS...JEFFERSON...KNOX...LOUDON...MEIGS...
RHEA...ROANE...UNION.
WIND ADVISORY UNTIL 7 PM EST /6 PM CST/ WEDNESDAY FOR THE
FOLLOWING ZONES: BLEDSOE...CAMPBELL...CLAIBORNE...MARION...
MORGAN...SCOTT TN...SEQUATCHIE.
VA...HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR THE FOLLOWING
ZONES: WASHINGTON.
WIND ADVISORY UNTIL 7 PM EST WEDNESDAY FOR THE FOLLOWING ZONES:
LEE...RUSSELL...SCOTT...WISE.
&&
$$
DH/TG
