415  
FXUS64 KMRX 081123  
AFDMRX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MORRISTOWN TN  
723 AM EDT WED APR 8 2020  
   
UPDATE
 
 
FOR 12Z AVIATION.  
 

 
   
SHORT TERM...(TODAY AND TONIGHT)
 
 
THE UPPER PATTERN THIS MORNING IS HIGHLIGHTED BY SPLIT FLOW WITH  
BROAD/FLAT RIDGING ANCHORED IN THE SOUTHERN STREAM ACROSS THE  
SOUTHEAST CONUS, WHILE THE NORTHERN STREAM REMAINS RATHER ZONAL,  
FOR NOW. AT THE SURFACE, A SERIES OF BOUNDARIES EXIST ACROSS THE  
OH VALLEY AND LOWER GREAT LAKES REGION, WITH ANTICYCLONIC FLOW  
DOMINATING OVER THE DEEP SOUTH. CURRENTLY ACROSS EAST TN AND  
SOUTHWEST VA/NC, LLV MOISTURE ADVECTION IS UNDERWAY AMIDST MODEST  
WLY/SWLY LLV FLOW WHICH IS SUPPORTING INCREASING LOW STRATUS, AND  
EVEN SOME WEAK SHOWER ACTIVITY MOVING IN OUT OF THE PLATEAU  
ASSOCIATED WITH A SUBTLE H5 IMPULSE.  
 
MOVING INTO/THROUGH WEDNESDAY, CONDITIONS ACROSS THE TN VALLEY WILL  
IMPROVE AS THE DAY PROGRESSES WITH THE AFOREMENTIONED LOW CLOUDS  
SCTING OUT TO FAVOR LOW CU AND AMPLE HEATING AMONGST SUSTAINED  
SLY/SWLY MOISTURE ADVECTION. WITH THAT, DID KEEP POPS MENTIONABLE  
ALBEIT LOW DURING PEAK HEATING AS ISO/SCT CONVECTION IS POSSIBLE  
ONCE CONVECTIVE TEMPS ARE REACHED (HIGHS IN THE 70S TO LOW 80S),  
WITH LOW CONFIDENCE IN PLACEMENT. MEANWHILE THE SYNOPTIC PATTERN  
REALLY STARTS TO AMPLIFY AS A FAST MOVING H5 WAVE/TROUGH DIVES OUT  
OF CANADA ACROSS THE NORTHERN ROCKIES INTO THE PLAINS, RESULTING IN  
SURFACE CYCLOGENESIS ACROSS MO/IL. THIS DEEPENING SURFACE LOW WILL  
PROPEL A FAST MOVING COLD FRONT INTO A VERY MOIST/UNSTABLE WARM  
SECTOR OVER THE OH VALLEY LATE MONDAY EVENING WITH AMPLE CONVECTION  
TO ACCOMPANY. THIS FRONTAL CONVECTION WILL THEN RACE ACROSS THE  
PLATEAU, THROUGH THE GREAT VALLEY, AND INTO THE SOUTHERN  
APPALACHIANS AROUND SUNRISE THURSDAY.  
 
PROFILES IN THE WARM SECTOR ACROSS EAST TN ARE FAIRLY IMPRESSIVE  
AHEAD OF THE CONVECTION (DESPITE THE TIMING) WITH VERY STEEP LAPSE  
RATES AMIDST DEEP DRY AIR AND UNIDIRECTIONAL/STRONG SHEER. AS FOR  
HAZARDS, NOTHING IS OFF THE TABLE AS LARGE HAIL AND DAMAGING WINDS  
ARE CERTAINLY THE PRIMARY THREATS, BUT AN ISOLATED TORNADO OR TWO  
CANNOT BE RULED OUT AS SOME EMBEDDED ROTATIONS ARE LIKELY.  
INSTABILITY DOES LOOK TO WAIN CLOSER TO DAYBREAK AS THE LINE OF  
CONVECTION MOVES EAST, MAINLY JUST ON DIURNAL TRENDS, THEREFORE  
WOULD EXPECT SOME GRADUAL WEAKENING CLOSER TO THE NC LINE. ALL  
SAID, SPC HAS UPGRADED AREAS GENERALLY WEST OF I75 TO AN ENHANCED  
RISK OF SEVERE THUNDERSTORMS, WHICH IS WHERE INSTABILITY/SHEAR ARE  
MAXIMIZED, WHILE THE REMAINDER OF THE AREA IS ESSENTIALLY FAVORED IN  
THE SLIGHT RISK CATEGORY. AS FOR TIMING SPECIFICS, THE CAMS SEEM TO  
BE IN FAIRLY GOOD AGREEMENT WITH ONLY ONE SLOWER OUTLIER. TYPICALLY  
THESE FRONTS OUTPERFORM AS FAR AS SPEED/TIMING THUS LEANED AWAY FROM  
THE SLOWER OUTLIER THEREBY FAVORING A FAST FROPA BETWEEN MIDNIGHT  
AND 5-6AM EASTERN TIME.  
 
CDG  
   
LONG TERM...(THURSDAY THROUGH TUESDAY NIGHT)
 
 
ON THURSDAY, THE UPPER LVL SHORTWAVE WILL HAVE TRANSITIONED INTO  
A DEEP LOW ACROSS THE GREAT LAKES WITH STRONG JET DYNAMICS ACROSS  
THE OHIO VALLEY. AT THE SURFACE, AN AREA OF LOW PRESSURE WILL BE  
LOCATED WELL NORTH OF THE AREA WITH A TRAILING COLD FRONT THROUGH  
THE APPALACHIANS. AT THE START OF THE PERIOD ON THURSDAY, WE MAY  
BE DEALING WITH THE TAIL END OF STRONG TO SEVERE THUNDERSTORMS  
ALONG THE COLD FRONT. HI-RES CAMS SUGGEST MUCH IF NOT ALL OF THIS  
ACTIVITY TO BE OUT OF THE AREA BY 12Z HOWEVER A LOT CAN CHANGE  
OVER THE NEXT 24 HOURS REGARDING HOW QUICK THIS ACTIVITY GETS  
THROUGH THE AREA. FOR MORE INFORMATION ON THE KINEMATIC AND  
THERMODYNAMIC ENVIRONMENT AHEAD OF THIS LINE PLEASE REFER TO THE  
SHORT TERM SEGMENT OF THIS AFD. OTHERWISE, WINDS QUICKLY TURN  
TOWARD THE NORTHWEST BEHIND THE FRONT ADVECTING A MUCH DRIER AND  
COOLER AIRMASS INTO THE TENNESSEE VALLEY. HIGHS ON THURSDAY SHOULD  
REACH THE MID TO UPPER 60S.  
 
CYCLONIC FLOW WILL STILL DOMINATE THE REGION ON FRIDAY WITH STRONG  
NORTHWEST FLOW IN PLACE ALOFT. HIGH PRESSURE AT THE SURFACE WILL  
QUICKLY FILTER IN UNDERNEATH THE DESCENDING BRANCH OF THE TROUGH.  
CONTINUED DRY AND COOLER WEATHER CONDITIONS ARE ANTICIPATED ON  
FRIDAY AND SATURDAY WITH INCREASING HEIGHTS ALOFT AND HIGH PRESSURE  
AT THE SURFACE. TEMPERATURES BOTH DAYS WILL BE MUCH COOLER WITH  
HIGHS IN THE 50S TO 60S. SATURDAY AND INTO SUNDAY, A NORTHERN BRANCH  
SHORTWAVE WILL QUICKLY EJECT SOUTH INTO THE NORTHERN PLAINS WHILE A  
SOUTHERN STREAM BEGINS TO PHASE OVER THE SOUTHERN PLAINS. STILL SOME  
MODEL DIFFERENCE REGARDING THE TIMING OF PHASING AS WELL AS WHERE  
THE RESULTING SURFACE LOW WILL TRACK. THIS WILL GREATLY DETERMINE  
ANY STRONG/SEVERE POTENTIAL INTO THE LATE WEEKEND AND EARLY NEXT  
WEEK. DO NOT WANT TO GET CAUGHT UP IN TO MANY DETAILS AT THIS POINT  
AS A LOT CAN CHANGE. WHAT IS MORE CONFIDENT IS THAT THE SHORTWAVE  
EMBEDDED WITHIN DEEP CYCLONIC FLOW ACROSS THE PLAINS WILL TRAVERSE  
THE TENNESSEE AND OHIO VALLEY LATE SUNDAY NIGHT INTO MONDAY.  
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO  
ACCOMPANY THIS WAVE. TEMPERATURES WILL MODERATE AS LOW LVL WINDS  
TURN TOWARD THE SOUTH AHEAD OF THIS WAVE.  
 
TUESDAY INTO WEDNESDAY CONFIDENCE IS LOW REGARDING HOW QUICK THE  
FRONT CAN KICK OUT. AS A RESULT WILL LIKELY KEEP LOW END POPS FOR  
TUESDAY AND TUESDAY NIGHT TO ACCOUNT FOR THIS. LOOKING AHEAD TO  
WEDNESDAY, ANOTHER SHOT OF COOLER AND DRIER WEATHER SHOULD ACCOMPANY  
THE DEPARTING FRONT.  
 
AD  
 

 
   
AVIATION
 
 
12Z TAF DISCUSSION.  
 
A MIXTURE OF VFR/MVFR AND POSSIBLY IFR DURING THIS TAF CYCLE. LLV  
MOISTURE CONTINUES TO INCREASE THIS MORNING THUS PROMOTING ISO  
SHRA WITH MVFR STRATUS AT ALL SITES. OTHERWISE, LOW VFR CU WILL  
PREVAIL BY LATE MORNING, PERHAPS WITH HEATING INDUCED SHRA/TSRA  
MOVING OUT OF KY TO AFFECT TRI. WINDS WILL REMAIN SWLY IN THE  
6-10KTS RANGE WITH GUSTS IN THE 20-25KTS RANGE THIS AFTERNOON.  
 
CDG  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
CHATTANOOGA AIRPORT, TN 82 61 69 44 60 / 20 80 10 0 0  
KNOXVILLE MCGHEE TYSON AIRPORT, TN 79 59 66 41 56 / 20 80 20 0 0  
OAK RIDGE, TN 79 58 66 40 57 / 20 80 10 0 0  
TRI CITIES AIRPORT, TN 73 55 64 37 53 / 30 90 30 0 0  
 

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

 
 

 
 
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