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 290711
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
311 AM EDT WED JUL 29 2015

.SHORT TERM...(TODAY AND TONIGHT)...AREAS OF DENSE FOG WILL BE
POSSIBLE THROUGH EARLY MORNING AS WE CURRENTLY HAVE A LOW
TEMP/DEWPOINT SPREADS ACROSS THE AREA COMBINED WITH FEW CLOUDS AND
CALM WINDS. FOG WILL CLEAR A FEW HOURS AFTER SUNRISE. PLEASE USE
CAUTION WHILE TRAVELING THROUGH AREAS OF DENSE FOG AS VISIBILITY MAY
SUDDENLY DECREASE.

TODAY WILL BE SIMILAR TO YESTERDAY IN TERMS OF AFTERNOON CONVECTION.
UPPER RIDGE TO OUR WEST WILL ALLOW US TO BE IN A MOSTLY UNCAPPED
ENVIRONMENT BY THE AFTERNOON HOURS. COVERAGE EXPECTED TO BE ISO/SCT.
A FEW STORMS COULD BE STRONG WITH ONE OR TWO POSSIBLY BECOMING
SEVERE DUE TO CAPES RANGING FROM 2000 TO 3000 J/KG ACROSS THE AREA.
THESE WILL BE PULSE STORMS DUE TO THE LACK OF SHEAR SO THEY WILL BE
SHORT LIVED. THE MAIN THREATS WILL BE HEAVY RAINFALL AND ISO
DAMAGING WIND GUSTS. TEMPS WILL RANGE FROM THE LOW TO MID 90S FOR
MOST OF THE AREA WITH HEAT INDICES RANGING FROM THE MID 90S TO NEAR
100. THOUGH THESE VALUES DON`T MEET ADVISORY CRITERIA PERSONS SHOULD
STILL EXERCISE CAUTION WHILE PERFORMING ANY OUTDOOR ACTIVATES DURING
THE AFTERNOON HOURS.

STORMS WILL LINGER INTO THE EVENING HOURS IN ADVANCE OF AN
APPROACHING COLD FRONT. STORMS WILL EVENTUALLY WAIN IN COVERAGE THE
FURTHER WE GET INTO THE NIGHT. OVERNIGHT LOWS WILL BE A FEW DEGREES
ABOVE NORMAL WITH LOWS IN THE LOW TO MID 7OS.


.LONG TERM...(THURSDAY THROUGH TUESDAY)...MODELS REALLY NOT IN VERY
GOOD AGREEMENT ON TIMING OF THE COLD FRONT ON THURSDAY...WITH NAM
ZIPPING THE COLD FRONT THROUGH OUR FORECAST AREA BY 12Z THURSDAY.
THIS RESULTS IN LESS THAN 10 PERCENT POPS FROM THE NAM MOS FOR
THURSDAY. I HAVE OPTED FOR NOW TO STAY CLOSER TO THE SIMILAR
GFS/ECMWF TIMING...WHICH SUPPORTS OUR PREVIOUS POP/WX GRIDS FOR
THURSDAY WITH CHANCE POPS. HOWEVER...BOTH THE GFS/ECMWF FRONTAL
TIMING WOULD ALLOW THE DROPPING OF POPS BY OR BEFORE 04Z FRIDAY.
TRENDED OUR GRIDS THAT WAY AND ALLOWED POPS TO DROP FROM THE NW BY
THURSDAY AFTERNOON...THEN JUST KEPT SLIGHT CHANCE POPS IN ERN MOST
COUNTIES THROUGH THURSDAY EVENING.

WE THEN SEE NW FLOW ALOFT ESTABLISHED AS THE UPPER RIDGE RETROGRADES
WESTWARD AND TROUGHING DEVELOPS OVER THE ERN THIRD OF THE NATION.
SURFACE RIDGING AT THE SAME TIME LOOKS TO SET UP ACROSS THE SE
STATES AND SRN APPALACHIANS FOR FRIDAY THROUGH THE WEEKEND. THIS
MADE THE SUPERBLEND 20 TO 30 PERCENT POPS ON SUNDAY AND MONDAY QUITE
SUSPECT...SINCE SURFACE WINDS STAY LIGHT AND VARIABLE DUE TO THE
RIDGE. DAYTIME HEATING ALONE LOOKS INSUFFICIENT TO CREATE MUCH IN
THE WAY OF SHOWERS OR THUNDERSTORMS...WITH VERY LIMITED LOW LEVEL
MOISTURE CONVERGENCE. GFSX AND ECMWX POPS FOR FRIDAY THROUGH MONDAY
WERE WELL BELOW CLIMO...SO I KEPT OUR GRIDS DRY UNTIL MONDAY
AFTERNOON TO TUESDAY NIGHT.

FOR TEMPS...WENT A LITTLE COOLER THAN GFS FOR THURSDAY MAXES GIVEN
THE POTENTIAL FOR MORNING AND AFTERNOON CONVECTION. THE GFS MOS
TEMPS LOOKED VERY GOOD FOR THURSDAY NIGHT AND FRIDAY. THE SUPERBLEND
MINS/MAXES WERE CLOSELY FOLLOWED FOR THE REST OF THE LONG TERM...
WITH A SLIGHT ADJUSTMENT TO GIVE MORE OF A RANGE IN MINS IN THE
MTNS.

&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             94  75  92  71 /  30  30  50  10
KNOXVILLE MCGHEE TYSON AIRPORT, TN  92  73  89  69 /  30  30  40  10
OAK RIDGE, TN                       92  74  90  67 /  30  30  40  10
TRI CITIES AIRPORT, TN              90  70  88  63 /  30  30  50  20

&&

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

&&

$$

SR/TG



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