169
FXUS64 KMRX 201725
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
125 PM EDT WED MAY 20 2026
..NEW DISCUSSION, AVIATION
KEY MESSAGES
UPDATED AT 122 PM EDT WED MAY 20 2026
- RAIN CHANCES INCREASE THIS AFTERNOON AND EVENING, WITH CONTINUED
HIGH RAIN CHANCES THROUGH THE FIRST HALF OF NEXT WEEK.
- ORGANIZED SEVERE STORMS APPEAR UNLIKELY DURING THIS FORECAST
PERIOD, BUT THE PRIMARY THREATS WITH STORMS EACH DAY WILL BE
LIGHTNING, LOCALLY HEAVY RAINFALL, AND SOME GUSTY WINDS.
DISCUSSION
ISSUED AT 122 PM EDT WED MAY 20 2026
CONVECTION HAS GOTTEN OFF TO AN EARLY START TODAY IN AN
INCREASINGLY MOIST AIR MASS, DEVELOPING IN MIDDLE TN AND THE
PLATEAU, WHICH IS AN AREA OF HIGHER SURFACE CAPE VALUES AROUND
1500 J/KG AND SURFACE CONFLUENCE. THERE IS LITTLE TO NO SHEAR TO
HELP SUSTAIN OR ORGANIZE THESE STORMS, SO THEY WILL MAINLY BE
DRIVEN BY OUTFLOW BOUNDARIES, TERRAIN, AND CONVERGENCE ZONES.
EXPECT THAT COVERAGE WILL INCREASE IN THE CENTRAL AND SOUTHERN TN
VALLEY OVER THE NEXT FEW HOURS. THE MAIN HAZARDS WILL BE LIGHTNING
AND SOME LOCALLY HEAVY RAINFALL THAT COULD CAUSE MINOR FLOODING
ISSUES.
ISOLATED TO SCATTERED SHOWERS ARE EXPECTED TO PERSIST THROUGH THE
NIGHT DUE TO THE MOISTURE RICH ENVIRONMENT, THE PRESENCE OF A
MIDLEVEL SHORTWAVE TROUGH, AND SOME UPPER DIVERGENCE. A FRONT IN THE
OH VALLEY REGION TODAY WILL MOVE SOUTHWARD AND BE NEAR OUR NORTHWEST
BORDER BY THURSDAY MORNING. THIS WILL ACT AS A FOCUS FOR CONVERGENCE
AND CONVECTIVE DEVELOPMENT THURSDAY. POPS WILL BE CATEGORICAL ACROSS
THE ENTIRE AREA, WITH A CHANCE OF THUNDERSTORMS. INSTABILITY AND
SHEAR WILL BE LACKING FOR ANY ORGANIZED SEVERE THREAT, ALTHOUGH SOME
GUSTY DOWNBURTS WINDS AND LOCALLY HEAVY RAINFALL WILL BE POSSIBLE.
A STRENGTHENING SOUTHERLY FLOW AHEAD OF A LOW OVER AR LIFTS THE
AFOREMENTIONED BOUNDARY NORTHWARD ON FRIDAY, PUTTING OUR AREA INTO
THE WARM SECTOR IN THE AFTERNOON. LREF JOINT PROBABILITIES OF CAPE >
1000 J/KG AND SHEAR > 25 KT ARE AROUND 30% ACROSS THE AREA, AND NEAR
40% IN OUR SOUTHERN SECTIONS WHERE CLOUDS MAY SCATTER ENOUGH TO
ENHANCE AFTERNOON HEATING. A FEW STRONG TO SEVERE STORMS CANNOT BE
RULED OUT FOR FRIDAY, BUT THE CHANCE REMAINS LOW.
A DEEP SW FLOW PERSISTS THROUGH THE WEEKEND AND EARLY NEXT WEEK,
WITH BROAD TROUGHING OVER THE CENTRAL US. DISTURBANCES EJECTING FROM
THIS BROAD TROUGH WILL BRING SEVERAL ROUNDS OF ENHANCED RAIN CHANCES
THROUGH EARLY NEXT WEEK, BUT THE TIMING OF THESE DISTURBANCES
REMAINS HIGLY UNCERTAIN. OVERALL, THE PATTERN FAVORS CONTINUED HIGH
RAIN CHANCES EACH DAY. THE PRIMARY IMPACTS WILL BE LIGHTNING AND
LOCALLY HEAVY RAINFALL. QPF THROUGH THE NEXT 7 DAYS WILL VARY WIDELY
ACROSS OUR AREA, DEPENDING ON WHICH AREAS SEE REPEATED SHOWERS AND
STORMS OVER NUMEROUS DAYS. GENERALLY SPEAKING, 1-3" OF RAIN IS
FORECAST THROUGH THE PERIOD.
AVIATION
(18Z TAFS)
ISSUED AT 122 PM EDT WED MAY 20 2026
SHOWERS AND STORMS WILL BE NEAR CHA OVER THE NEXT FEW HOURS, AND MAY
BRING TS WITH MVFR/ VIS/CIGS. THIS ACTIVITY MAY SPREAD TOWARD TYS
LATER IN THE EVENING, AND POTENTIALLY TO TRI LATER IN THE NIGHT.
WITH A MOIST BOUNDARY LAYER, LOW CLOUDS AT MVFR LEVELS ARE EXPECTED
TO FORM AND PERSIST INTO TOMORROW MORNING, BUT THIS MAY BE DEPENDENT
ON WHETHER SHOWERS PASS OVER THE TERMINALS THIS EVENING. CONFIDENCE
OF THIS HAPPENING IS HIGH AT CHA, MEDIUM AT TYS, AND LOW AT TRI.
PRELIMINARY POINT TEMPS/POPS
CHATTANOOGA AIRPORT, TN 89 66 84 66 / 70 50 80 80
KNOXVILLE MCGHEE TYSON AIRPORT, TN 89 66 83 65 / 50 50 90 70
OAK RIDGE, TN 88 64 82 63 / 60 40 90 70
TRI CITIES AIRPORT, TN 88 63 81 62 / 30 60 80 60
MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...NONE.
VA...NONE.
DISCUSSION...DGS
AVIATION...DGS
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