107
FXUS64 KMRX 041753
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
153 PM EDT MON MAY 4 2026
..NEW DISCUSSION
KEY MESSAGES
UPDATED AT 145 PM EDT MON MAY 4 2026
- WIDESPREAD SHOWERS AND STORMS TUESDAY NIGHT THROUGH THURSDAY
MORNING.
- PERIODS OF HEAVY RAIN ARE LIKELY. SOME FLOODING CONCERNS ARE
POSSIBLE GIVEN THE POTENTIAL FOR TRAINING SHOWERS AND STORMS ON
WEDNESDAY.
- A CONDITIONAL SEVERE WEATHER THREAT EXISTS ON WEDNESDAY IF
SURFACE-BASED INSTABILITY CAN DEVELOP.
DISCUSSION
ISSUED AT 145 PM EDT MON MAY 4 2026
MAIN CONCERN FOR THE NEXT 7 DAYS WILL BE THE SYSTEM MOVING THROUGH
THE REGION ON WEDNESDAY SO THE DISCUSSION WILL FOCUS ON THAT. THIS
WILL BRING WITH IT THE POSSIBILITY OF SOME FLASH FLOODING CONCERNS,
AS WELL AS A CONDITIONAL SEVERE WEATHER THREAT. GUSTY WINDS WILL BE
POSSIBLE IN THE MOUNTAINS TUE NIGHT INTO WED THANKS TO A STRONG LOW
LEVEL JET, BUT OTHERWISE MOSTLY DRY CONDITIONS ARE IN STORE FOR THE
FORECAST AREA THROUGH THE PERIOD.
A SYNOPTIC SCALE TROUGH WILL DROP OUT OF CENTRAL/EASTERN CANADA
INTO THE NORTHERN CONUS TODAY AND TONIGHT, WHILE A CLOSED UPPER LOW
SLOWLY MOVES ASHORE OVER SOUTHERN CALIFORNIA. EVENTUALLY THE UPPER
LOW OPENS UP AND ANCHORS THE WESTERN PERIPHERY OF THE CANADIAN
TROUGH, ALLOWING THE NORTHERN AND SOUTHERN STREAM JETS TO MERGE OVER
THE CENTRAL CONUS TUE INTO WED. THE RESULT WILL BE WIDESPREAD
SOUTHWESTERLY FLOW DEVELOPING OVER THE DEEP SOUTH AND LOWER
MISSISSIPPI RIVER VALLEY TONIGHT THROUGH THE MID WEEK TIME FRAME. AT
THE SURFACE, CYCLOGENESIS WILL TAKE PLACE ACROSS THE SOUTHERN PLAINS
ON TUESDAY, WITH A COLD FRONT SETTING UP SOMEWHERE FROM THE ARKLATEX
REGION ENE INTO EASTERN KENTUCKY BY TUE NIGHT. ALL OF THIS WILL LEAD
TO A PLUME OF GULF MOISTURE SURGING NORTHEAST FROM THE TEXAS COAST
INTO THE APPALACHIAN REGION, WITH PWATS EXCEEDING 1.75" ACROSS PARTS
OF THE AREA BY WED AFTERNOON BEFORE THE COLD FRONT PUSHES THROUGH
WED NIGHT INTO EARLY THU MORNING.
FLOODING/FLASH FLOODING CONCERNS:
LOW AND MID LEVEL FLOW WILL BE PARALLEL TO THE FRONT AS IT
APPROACHES, WITH SEVERAL WAVES OF SURFACE LOW PRESSURE FORECAST TO
DEVELOP AND MOVE NORTHEAST ALONG THE FRONT TUE NIGHT THROUGH WED.
ALL OF THIS POINTS TO A SLOW MOVING BOUNDARY WHICH, WHEN COUPLED
WITH A MODEST AMOUNT OF INSTABILITY, SUFFICIENT SHEAR, AND HIGH
PWATS WILL MEAN A CHANCE OF TRAINING SHOWERS AND THUNDERSTORMS
CAPABLE OF PRODUCING HEAVY RAINS AND SOME FLASH FLOODING ISSUES. THE
HEAVIEST RAIN LOOKS TO BE FOCUSED ON AREAS SOUTH OF THE I-40
CORRIDOR, WHICH IS WHERE DROUGHT CONDITIONS ARE THE MOST SEVERE AT
THE MOMENT. AND ALTHOUGH RAIN IS NEEDED, HEAVY RAINS ON DROUGHT
STRICKEN SOIL IS NOT IDEAL. CURRENTLY THE FORECAST CALLS FOR 2-3" OF
STORM TOTAL RAIN ACROSS THE SOUTHERN HALF OF THE FORECAST AREA AND
ESPECIALLY IN THE SOUTHERN TN MOUNTAINS, WHICH IS SUPPORTED BY
ENSEMBLE DATA SHOWING VERY HIGH ODDS OF EXCEEDING 1.5" ACROSS A
LARGE SWATH OF THE SOUTHERN HALF OF THE CWA TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT. AND GIVEN THE PATTERN, I WOULD NOT BE AT ALL
SURPRISED TO SEE THIS EXCEEDED IN SPOTS IF THERE IS ANY DECENT
TRAINING OF THUNDERSTORMS. FURTHERMORE, WPC HAS THE SOUTHERN PARTS
OF THE CWA HIGHLIGHTED BY A DAY 3 EXCESSIVE RAIN OUTLOOK, SO THIS
ALL SEEMS REASONABLE.
SEVERE WEATHER CONCERNS:
DEPENDING ON THE LOCATION OF THE FRONT WED AFTERNOON AND EVENING,
AND THE THERMAL PROFILES IN PLACE, THERE COULD BE JUST ELEVATED
INSTABILITY WITH HEAVY RAINS AND NO REAL THREAT OF SEVERE STORMS. OR
THERE COULD BE THE POTENTIAL FOR DAMAGING WINDS AND EVEN A
CONDITIONAL TORNADO RISK IN THE SOUTH. JOINT PROBABILITIES FROM
ENSEMBLE DATA SHOW ABOUT A 30-35 PERCENT CHANCE OF HAVING SURFACE-
BASED INSTABILITY EXCEEDING 500 J/KG AND BULK SHEAR OF 40KT OR
GREATER WED AFTERNOON AND EVENING ACROSS THE SOUTHERN TN VALLEY. I
DON'T HAVE HIGH CONFIDENCE IN EXACTLY HOW THIS WILL PLAY OUT BECAUSE
THAT WILL DEPEND ON MESOSCALE DETAILS THAT WE'RE NOT PRIVY TO JUST
YET (E.G. WHERE AND WHEN DO THE WAVES OF SURFACE LOW PRESSURE
DEVELOP ALONG THE FRONT AND PASS BY/THROUGH OUR CWA, AND WHAT ARE
THE EFFECTS ON THE LOW LEVEL THERMAL PROFILES). HOWEVER, THERE'S
PLENTY OF SHEAR IN PLACE AND IF WE CAN DEVELOP SURFACE BASED
INSTABILITY THEN DAMAGING WINDS AND EVEN A TORNADO CAN'T BE RULED
OUT OVER THE SOUTHERN VALLEY AND PLATEAU AREAS WED AFTERNOON AND
EVENING. CURRENTLY THE FAR SOUTH IS OUTLOOKED IN A DAY 3 MARGINAL
RISK AREA BY SPC AND THAT SEEMS REASONABLE GIVEN THE UNCERTAINTIES.
I WOULDN'T BE SURPRISED IF THERE IS AN INCREASE IN SEVERE CHANCES
OVER THE NEXT 24 HOURS THOUGH AS THE EVENT COMES INTO VIEW OF THE
CAM GUIDANCE.
AVIATION
(18Z TAFS)
ISSUED AT 107 PM EDT MON MAY 4 2026
VFR CONDITIONS EXPECTED AT ALL SITES THROUGH THE PERIOD. ASIDE
FROM GUSTY SOUTH-SOUTHWEST WINDS AT TYS THIS AFTERNOON, WINDS
SHOULD BE AROUND 10KTS OR LESS THROUGH THE PERIOD AND MOSTLY
SOUTH-WESTERLY.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 54 79 63 77 / 0 20 50 80
KNOXVILLE MCGHEE TYSON AIRPORT, TN 54 79 61 75 / 0 20 70 90
OAK RIDGE, TN 52 77 60 73 / 0 20 70 90
TRI CITIES AIRPORT, TN 48 78 58 74 / 0 10 60 90
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...CD
AVIATION...99
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