269
FXUS64 KMRX 222328
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
728 PM EDT FRI OCT 22 2021
UPDATE
FOR 00Z AVIATION.
SHORT TERM...(TONIGHT AND TOMORROW)
KEY MESSAGES:
1. ISOLATED AREAS OF FOG/DENSE FOG ARE POSSIBLE OVERNIGHT BUT
CONFIDENCE ON OCCURRENCE AND COVERAGE IS VERY LOW.
DISCUSSION:
PLENTY OF CLOUD COVER REMAINS THIS AFTERNOON BEHIND A COLD FRONTAL
PASSAGE THAT BROUGHT RAIN AND STORMS YESTERDAY. GRADUAL CLEARING IS
EXPECTED INTO THE OVERNIGHT HOURS BUT SOME CLOUD COVER WILL REMAIN.
AREAS THAT SEE CLEARING WILL HAVE A BETTER CHANCE OF FOG DEVELOPING.
ALTHOUGH ISOLATED, SOME OF THE FOG COULD BE LOCALLY DENSE.
UPPER JET AND 500MB SHORTWAVE DIP BACK DOWN INTO OUR AREA OVERNIGHT
BUT THE BEST LIFT REMAINS TO OUR NORTH. UPPER JET/SHORTWAVE
COMBINED WITH LINGERING MOISTURE AND UPSLOPE FLOW MAY BE ENOUGH TO
SQUEEZE OUT A FEW SPRINKLES ACROSS THE MOUNTAINS OF NORTHEAST TN AND
SOUTHWEST VA. CONFIDENCE IS LOW THAT THIS OCCURS SO KEPT THE
FORECAST DRY.
THE FLOW BECOMES MORE ZONAL TOMORROW AS HIGH PRESSURE PUSHES IN FROM
THE SOUTHWEST. WITHIN THIS ZONAL FLOW A WEAK DISTURBANCE MOVES
ACROSS OUR AREA TOMORROW AFTERNOON. DON'T ANTICIPATE PRECIP BUT THIS
FEATURE WILL INCREASE CLOUD COVER AS IT MOVES ACROSS DURING THE
AFTERNOON HOURS. HOWEVER, MOST PLACES SHOULD SEE A GOOD AMOUNT OF
SUNSHINE FOR THE FIRST HALF OF THE DAY.
SR
LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
KEY MESSAGES:
1. ACTIVE LONG TERM PERIOD WITH A SYSTEM ON MONDAY, AND ANOTHER ONE
MID TO LATE NEXT WEEK.
2. HOWEVER, CONFIDENCE IN THE FORECAST IS PRETTY LOW BEYOND TUESDAY
NIGHT.
DISCUSSION:
SATURDAY NIGHT THROUGH SUNDAY LOOKS TO BE DRY. SURFACE LOW PRESSURE
DEVELOPS IN THE CENTRAL PLAINS LATE SAT NIGHT INTO SUN MORNING AS A
SHORTWAVE EJECTS EAST FROM THE COLORADO ROCKIES. EAST TN SHOULD BE
FIRMLY IN THE WARM SECTOR OF THIS DEVELOPING SYSTEM, WITH ANY
PRECIPITATION ASSOCIATED WITH ISENTROPIC ASCENT LOCATED TO OUR WEST
AND NORTHWEST WHERE BETTER FORCING WILL BE. EXPECT A FAIRLY WARM DAY
ON SUNDAY AS A RESULT, WITH HIGHS WELL INTO THE 70S, POSSIBLY
APPROACHING 80 DEGREES IN THE TN VALLEY (AS SOME MOS GUIDANCE IS
SUGGESTING).
MATURING MID-LATITUDE CYCLONE SHIFTS TO NORTHERN IL/IN BY MONDAY
MORNING, WITH TRAILING COLD FRONT SHIFTING EAST THROUGH TN DURING
THE DAY. RAINFALL LOOKS TO REACH THE TN VALLEY BY LATE MORNING OR
MIDDAY TIME FRAME. TRENDED TOWARDS THE OPERATIONAL MODELS WITH
RESPECT TO ONSET OF RAINFALL ON MONDAY; NBM WAS A LITTLE TO QUICK I
THOUGHT. HAVE MOSTLY SHOWERS MENTIONED, WITH A SLIGHT CHANCE OF
THUNDER DUE TO WEAK INSTABILITY ALOFT. THE COLD FRONT CLEARS THE
AREA TO THE EAST MONDAY EVENING, BUT THE UPPER SHORTWAVE RESPONSIBLE
FOR THIS SYSTEM PHASES WITH ANOTHER WAVE TO FORM A DEEP UPPER LOW
OVER THE EASTERN GREAT LAKES BY TUESDAY MORNING. RESULTING LOW LEVEL
NW FLOW REGIME LOCALLY WILL LIKELY PRODUCE SOME SHOWERS IN THE
MOUNTAINS THROUGH THE DAY TUESDAY BUT EXPECT RAINFALL TO WIND DOWN
BY LATE TUESDAY.
TO OUR WEST, STRONG UPPER RIDGING TRAVERSES THE MISSISSIPPI RIVER
VALLEY DURING THE DAY TUESDAY AHEAD OF ANOTHER DEEP UPPER TROUGH
MOVING OFF THE ROCKIES. MODELS ARE NOT IN GOOD AGREEMENT WITH THE
DETAILS ON HOW THE PATTERN UNFOLDS FOR WEDNESDAY ONWARD. ONE THING
THAT APPEARS CERTAIN IS THAT RAIN CHANCES WILL INCREASE
SIGNIFICANTLY LATE WEDNESDAY AFTERNOON THROUGH THE END OF THE PERIOD
AS A STRONGLY, NEGATIVELY TILTED UPPER TROUGH MOVES EAST THROUGH THE
CONUS. DEPENDING ON HOW THIS EVOLVES WE MAY NEED TO WATCH FOR SEVERE
POTENTIAL LATE WEDNESDAY. HOWEVER, THAT IS HIGHLY DEPENDENT ON THE
DETAILS WHICH ARE BY NO MEANS CLEAR AT THIS TIME.
CD
AVIATION
00Z TAF DISCUSSION.
MAIN CONCERN FOR THE TAF PERIOD IS POTENTIAL OF FOG DEVELOPMENT AT
CHA WITH THE POSSIBILITY OF MVFR CONDITIONS BETWEEN 09-12Z. LOW
PROBABILITY OF MARGINAL MVFR AT TYS. CLOUD COVER WILL INHIBIT FOG
DEVELOPMENT AT TRI.
OTHERWISE, CEILING AROUND 3500-4500FT CAN BE EXPECTED AT THE TAF
SITES WITH A SLOW DIMINISHING THROUGH THE NIGHT AND EARLY SATURDAY
MORNING FROM CHA-TYS-TRI.
WINDS WILL GENERALLY BE BELOW 10KTS THROUGH THE FORECAST PERIOD.
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
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