140  
FXUS64 KMRX 220750  
AFDMRX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MORRISTOWN TN  
350 AM EDT SUN OCT 22 2017  
   
SHORT TERM...(TODAY AND TONIGHT)
 
 
CURRENT WATER VAPOR IMAGERY AND RAP UPPER AIR ANALYSIS INDICATE  
AN UPPER LEVEL RIDGE STRETCHING N-S ALONG THE EASTERN SEABOARD  
WITH A TROUGH ACROSS THE CENTRAL AND SOUTHERN PLAINS. NOT SEEING  
AS MUCH FOG EARLY THIS MORNING WITH CLOUD COVER INCREASING AHEAD  
OF THE SYSTEM BACK TO THE WEST. PW VALUES ARE STILL FAIRLY LOW  
ACROSS THE AREA WITH VALUES RANGING FROM AROUND 0.4-0.6 INCHES,  
WHICH IS AROUND THE 10TH-25TH PERCENTILE FOR LATE OCTOBER. TODAY  
WILL BE A TRANSITION DAY ACROSS THE REGION AS MOISTURE ADVECTION  
INCREASES WITH LOW TO MIDLEVEL SOUTHERLY FLOW AS THE SHORTWAVE  
TROUGH MOVES INTO THE MISSISSIPPI RIVER VALLEY. TEMPERATURES WILL  
BE ABOVE NORMAL AGAIN TODAY AS WARM AIR ADVECTS INTO THE REGION  
WITH HIGHS RANGING FROM THE MID TO UPPER 70S ACROSS MOST VALLEY  
LOCATIONS. MODEL SOUNDINGS INDICATE THAT THE ATMOSPHERE WILL  
SATURATE FROM THE TOP-DOWN TONIGHT WITH BEST CHANCES FOR SHOWERS  
COMING AFTER MIDNIGHT. PW VALUES WILL EVENTUALLY INCREASE INTO THE  
1.4-1.6 INCH RANGE BY EARLY MONDAY MORNING. THEREFORE, EXPECT  
WIDESPREAD SHOWERS EARLY MONDAY MORNING. NOT SEEING MUCH IN THE  
WAY OF INSTABILITY OVERNIGHT WITH LAPSE RATES NEAR MOIST ADIABATIC  
AND HAVE NOT INCLUDED ANY THUNDER CHANCES IN THE FORECAST FOR  
NOW. OVERNIGHT LOWS WILL BE ABOVE NORMAL WITH TEMPERATURES RANGING  
FROM THE UPPER 50S TO MID 60S.  
   
LONG TERM...(MONDAY THROUGH SATURDAY)
 
 
A HEALTHY SHORT WAVE TROUGH WILL SWING NORTHEAST OUT OF THE DEEP  
SOUTH, LIFTING A BROAD PATTERN OF SHOWERS AND EVEN A THUNDERSTORM  
OR TWO ACROSS SOUTHERN PARTS OF THE FORECAST AREA ON MONDAY. THE  
PRECIPITATION WILL TAPER OFF FROM SOUTHWEST TO NORTHEAST LATER  
MONDAY INTO MONDAY NIGHT HOWEVER, AN AMPLIFYING LONG WAVE TROUGH  
WILL BE DROPPING SOUTHEAST OUT OF THE WESTERN GREAT LAKES ACROSS  
THE SOUTHERN APPALACHIANS BRINGING MORE UNSETTLED WEATHER TO THE  
REGION. DEEP MOISTURE WRAPPED UP IN THE CIRCULATION OF THE TROUGH  
WILL BE LIFTED IN ASSOCIATION WITH A SHORT WAVE ROTATING THROUGH  
THE BASE OF THE MAIN UPPER LEVEL FEATURE. THEREFORE, CHANCE  
PROBABILITIES FOR A FEW LIGHT SHOWERS WILL REMAIN IN THE FORECAST  
ON TUESDAY. YET ANOTHER, WEAK UPPER WAVE WILL TRAIL BEHIND  
TUESDAY'S SYSTEM BRINGING A SLIGHT CHANCE FOR A COUPLE MORE  
SHOWERS ACROSS NORTHERN SECTIONS OF THE FORECAST AREA ON  
WEDNESDAY. THE UNSETTLED REGIME FINALLY ENDS ON THURSDAY AS HIGHER  
PRESSURE FILLS IN BEHIND THE DEPARTING AMPLIFIED EASTERN U.S.  
TROUGH. WE MAY BE ABLE TO SQUEEZE OUT A DRY PERIOD OF WEATHER  
WHICH LASTS ALL THE WAY THROUGH FRIDAY NIGHT WHILE AWAITING THE  
ARRIVAL OF THE NEXT MID LATITUDE CYCLONE AND ASSOCIATED PATTERN OF  
SHOWERS AND POSSIBLE THUNDERSTORMS ON SATURDAY. TEMPERATURES WILL  
BE MUCH CLOSER TO NORMAL FOR LATE OCTOBER DURING THE WORK WEEK  
WITH THE COOLEST DAY BEING WEDNESDAY WITH HIGHS ONLY REACHING THE  
LOWER TO MIDDLE 50S. A GRADUAL WARMING TREND WILL OCCUR THURSDAY  
INTO THE WEEKEND AS WINDS BECOME SOUTHERLY AHEAD OF THE WEEKEND  
FRONTAL SYSTEM.  
 

 
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
CHATTANOOGA AIRPORT, TN 78 65 69 50 / 0 90 100 40  
KNOXVILLE MCGHEE TYSON AIRPORT, TN 78 62 68 49 / 0 30 90 50  
OAK RIDGE, TN 78 62 67 49 / 0 60 90 50  
TRI CITIES AIRPORT, TN 77 58 69 48 / 0 30 90 80  
 

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

 
 

 
 
MA  
 
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