527
FXUS64 KMRX 231942
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
342 PM EDT SAT MAR 23 2019
SHORT TERM...(TONIGHT AND SUNDAY)
DEW POINTS HAVE REMAINED VERY DRY THIS AFTERNOON WITH MANY LOWER
ELEVATION AREAS STAYING IN THE LOW TO MID 20'S. A FEW AWOS SITES
HAVE HAD UPPER TEENS. LUCKILY WINDS HAVE BEEN VERY LIGHT UNDERNEATH
THE SURFACE HIGH WITH GENERALLY 3 TO 8 KNOT NORTH TO NORTHEAST FLOW.
SUBSIDENCE FROM THIS HIGH HAS AIDED IN THESE LOWER DEW POINTS EVEN
THOUGH THE SOURCE REGION UPSTREAM HAD HIGHER DEW POINTS THIS
MORNING.
HEIGHTS WILL BEGIN TO RISE TONIGHT AS AN H5 TROUGH DEVELOPS IN THE
PLAINS WITH A SURFACE LOW MOVING IN THAT VICINITY. THIS SYSTEM WILL
MOVE EASTWARD ON SUNDAY WHILE HIGHER HEIGHTS HOLD OVER THE TN VALLEY
AS THE SURFACE HIGH SETTLES OFF THE MID ATLANTIC COAST. THIS PATTERN
WILL YIELD WAA ACROSS EAST TN, SOUTHWEST VA, AND SOUTHWEST NC
BEGINNING TONIGHT AND LASTING THROUGH SUNDAY.
EXPECT LOW TEMPS TONIGHT TO AVERAGE A COUPLE OF DEGREES WARMER THAN
LAST NIGHT. A 10-20 KT SOUTHWESTERLY 850-700 MB JET WILL BEGIN TO
TRANSPORT WARMER AND MORE MOIST AIR INTO THE REGION AFTER 06Z, AND
PROJECTED SOUNDINGS FROM THE LATEST NAM12 SHOW SOME MID LEVEL
MOISENING AS THE NIGHT GOES ON WHICH SHOULD RESULT IN MID TO HIGH
LEVEL CLOUDS INCREASING. THESE FACTORS WILL LEAD TO THE MILDER NIGHT
WITH NO FROST CONCERNS. STAYED CLOSE TO MAV GUIDANCE FOR LOWS.
WARM, MOIST ADVECTION WILL CONTINUE SUNDAY WITH MIDLEVEL RH
INCREASING THROUGH THE DAY. THIS WILL LEAD TO PARTLY SUNNY TO MOSTLY
CLOUDY SKIES, BUT A WARM DAY IS IN STORE WITH MID TO UPPER 60'S IN
MUCH OF THE VALLEY AND SOME LOW 70'S LIKELY NEAR CHA. A 50+ KNOT 300
MB JET STREAK MOVING OVERHEAD LATE IN THE AFTERNOON OR EARLY IN THE
EVENING COULD GENERATE SCATTERED SHOWERS WELL AHEAD OF THE SYNOPTIC
COLD FRONT, SO INTRODUCED SLIGHT CHANCE POPS BETWEEN 21Z SUNDAY AND
00Z MONDAY. LEANED TOWARD THE SLIGHTLY WARMER MAV GUIDANCE FOR HIGHS.
LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
THE LONG RANGE PERIOD WILL FEATURE A DISTURBANCE MONDAY WITH
SHOWERS AND THUNDERSTORMS, WHILE THE MID TO LATE WEEK FEATURES
INCREASED TEMPERATURES AND DRY WEATHER. SUNDAY NIGHT, A
DISTURBANCE WILL TRAVERSE THE AREA. MODELS ARE NOT IN GREAT
AGREEMENT IN HOW THIS SYSTEM PROGRESS WITH THE NAM INDICATING THE
LEAD SHORTWAVE ACROSS THE OHIO VALLEY LEADING A SECONDARY WAVE
MOVING THROUGH THE SOUTHEAST. THE EURO INDICATES A MORE PHASED
SYSTEM WITH ONE SHORTWAVE TROUGH AS IT MOVES THROUGH THE TENNESSEE
VALLEY. THE GFS IS ALIGNED MORE WITH THE EURO WITH ONE SHORTWAVE.
THIS WILL LIKELY HAVE IMPLICATIONS ON TIMING OF THE FRONTAL
PASSAGE AND BEST COVERAGE OF SHOWERS AND THUNDERSTORMS ON MONDAY.
THE SURFACE REFLECTION FEATURES AN AREA OF LOW PRESSURE ACROSS THE
OHIO VALLEY THAT WILL MOVE INTO SOUTHERN APPALACHIANS BY MONDAY
NIGHT.
A COLD FRONT ATTENDANT THIS SURFACE LOW WILL MOVE THROUGH THE AREA
ON MONDAY, ALTHOUGH AS MENTIONED ABOVE, TIMING IS STILL UNCERTAIN.
THIS FRONT WILL LIKELY BEGIN TO WASH OUT AS IT MAKES ITS PASSAGE
THROUGH THE AREA LIMITING CONVERGENCE ALONG THE FRONT. THE WARM
SECTOR AIRMASS CHARACTERIZED BY MOISTURE AND INSTABILITY, ALBEIT
WEAK, WILL LEAD TO WIDESPREAD COVERAGE OF SHOWER ACTIVITY EARLY ON
MONDAY. ISOLATED TO SCATTERED THUNDERSTORMS ARE POSSIBLE ALONG THE
FRONT WHERE WEAK INSTABILITY EXISTS. A COUPLE OF LIMITING FACTORS
FOR WIDESPREAD COVERAGE OF THUNDERSTORMS IS THE MID-LEVEL FLOW
DISPLACED FURTHER SOUTH, AND WEAK FRONTAL CONVERGENCE. WILL BE
WATCHING THE MONDAY SYSTEM CLOSELY FOR ANY CHANGES, AS SOME SMALL
HAIL COULD OCCUR IN ANY STRONGER STORMS AS WETBULB ZERO HEIGHTS ARE
LOW, IN THE 6 TO 7 KFT RANGE. HOWEVER CONFIDENCE IS LOW IN ORGANIZED
SEVERE WEATHER.
RAIN WILL END FROM WEST TO EAST MONDAY NIGHT INTO TUESDAY WITH THE
EXIT OF THE SHORTWAVE TROUGH AND COLD FRONT. NORTHWEST FLOW ALOFT
SHOULD PROVIDE AT LEAST SOME LIFT IN THE FORM OF OROGRAPHICALLY
ENHANCED FLOW TO PROVIDE A FOCUS FOR CONTINUED PRECIPITATION CHANCES
FOR THE HIGHER TERRAIN ALONG THE PLATEAU, AND SMOKY MOUNTAINS.
SURFACE HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY TUESDAY
PROVIDING A NORTHERLY SURFACE FLOW. THIS SHOULD KEEP CONDITIONS
COOLER MONDAY NIGHT AND TUESDAY WITH HIGHS ON TUESDAY IN THE 50'S.
THE MAIN STORY FOR THE MID TO LATE WEEK PERIOD IS THE INCREASE IN
TEMPERATURES. UPPER LEVEL HEIGHTS WILL BE ON THE RISE WITH HIGH
PRESSURE LOCATED OFF SHORE THE MID-ATLANTIC PROVIDING A SOUTHERLY
FETCH NEAR THE SURFACE AND LOWER TROPOSPHERE. DRIER WEATHER WITH
HIGHS IN THE 60'S TO NEAR 70 DEGREES ARE LIKELY WITH LOWS IN THE 40
TO 50'S. ANOTHER SYSTEM WILL BEGIN TO APPROACH THE AREA BY FRIDAY
AND SATURDAY. DETAILS ARE STILL VERY UNCERTAIN IN REGARDS TO THE
SYNOPTIC PATTERN BUT IT SEEMS AN AMPLIFICATION IN THE UPPER LEVELS
WILL PROVIDE A DEEP TROUGH ACROSS THE WESTERN US, WITH RIDGING
ACROSS THE EAST. FOR NOW DECIDED TO FOLLOW A CMC AND EURO BLEND AS
THESE SEEM TO BE IN BETTER AGREEMENT. LATER FORECASTS WILL REFINE
THESE LARGE SCALE UNCERTAINTIES.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 42 73 53 66 / 0 20 60 80
KNOXVILLE MCGHEE TYSON AIRPORT, TN 41 69 51 63 / 0 10 60 80
OAK RIDGE, TN 40 69 51 64 / 0 20 70 70
TRI CITIES AIRPORT, TN 34 70 47 60 / 0 10 50 80
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
RG/AD
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