Sunrise 6:39 AM   Sunset 8:26 PM Moonrise 3:07 AM   Moonset 2:30 PM

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FXUS64 KMRX 031101 AFDMRX

Area Forecast Discussion National Weather Service Morristown TN 701 AM EDT Fri May 3 2024

New AVIATION

SHORT TERM
(Today and tonight)
Issued at 330 AM EDT Fri May 3 2024

Key Messages:

1. Increasing chances of showers and storms this morning through the evening, with a potential lull in activity overnight.

2. While severe weather is not expected, a few instances of small hail, wind gusts up to 40 mph, and locally heavy downpours are possible this afternoon.

Discussion:

Upper level disturbances will bring increasing chances of showers and storms to the forecast area today. Regional mosaic radar already depicts a rain shield moving into western Kentucky, central Tennessee, and eastern Mississippi this morning. Precipitation chances will gradually increase across our forecast area through the morning hours, with just general rain showers as the predominant weather type. As we transition into the afternoon hours, hi-resolution models suggest development of MLCAPE in the 300-800 J/kg range, which will lead to increasing chances of thunder. A weak shear profile and mid level lapse rates struggling to reach 6C/km should keep any storms from reaching severe levels, although, any stronger storm could lead to locally gusty winds up to 40mph and pea-size hail. PWAT values will generally approach near 1.4 inches. This is around the 90th percentile based on sounding climatology out of BNA. As such, we cannot totally rule out some isolated flooding concerns with any slow moving or training convection this afternoon. Thankfully, below normal rainfall over the last month has allowed for 1 hr FFGs of 1.8-2.3" across the forecast area, really minimizing this threat. A marginal risk for excessive rainfall covers areas generally along and west of I-75 - where the better chance for relatively more effective convection exists. Temperatures will typically be near normal. Ensemble guidance suggest we may see a window of little to no activity during the late evening/overnight hours.

LONG TERM
(Saturday through Thursday)
Issued at 330 AM EDT Fri May 3 2024

Key Messages:

1. An unsettled pattern is expected through the extended period with daily scattered to numerous showers and storms. More organized convection is possible by Wednesday/Thursday of next week.

2. Temperatures will be generally above normal, especially next week.

Saturday through Monday

At the start of the period, a fairly weak upper-level flow pattern will be in place with a shortwave moving in from the west. With broad moisture and surface heating, Saturday will consist of scattered to numerous convection throughout the day. Based on the weak flow, the convection will be thermodynamically-driven as very minimal shear will be present. Overall, instability will be fairly typical of the summer, i.e. near 1,000 J/kg of MLCAPE. PWATs will also be 1.4 inches or higher, which is around the 90th percentile for this time of year. With these conditions, some stronger storms with gusty downburst winds are possible, in addition to locally heavy rainfall rates. Thankfully, fairly dry conditions, including low-end drought, will keep any flooding concerns very localized.

Heading towards Sunday, gradual height rises are expected with embedded shortwave energy and similar thermodynamic conditions. This will lead to slightly warmer temperatures than on Saturday with additional showers and storms expected. A closed upper low will also be noted to our west and will approach towards Monday. This may lead to slightly better coverage than on Sunday, but the overall impact will be the same.

Tuesday through Thursday

The unsettled pattern will continue into the middle of the week with continued embedded shortwave, broad moisture, and surface heating on Tuesday. By Wednesday to Thursday, however, a more dynamic pattern is anticipated with the upper jet (in excess of 100 kts) dipping further south. Upper-level divergence will help to strengthen the 850mb, possibly to in excess of 40 kts. A surface front will also slowly drift southward. While discrepancies still exist, these indications suggest an environment with potentially better thermodynamics and deep-layer shear sufficient for more organized convection than in the earlier part of the extended period. At this time, low probability HWO wording will be kept to encompass the multiple rounds of convection and potential locally heavy rainfall.
However, the Wednesday to Thursday timeframe will be something to watch for more organized and/or robust convection.

AVIATION
(12Z TAFS)
Issued at 659 AM EDT Fri May 3 2024

VFR conditions will be predominant through the TAF cycle, with mid to low level BKN/OVC clouds increasing through the morning into the afternoon. Continue to expect increasing chances for a few thunderstorms by the afternoon. Rain chances increase late morning to mid-day at TRI but have kept thunder omitted. Recent hi- resolution guidance suggest by late Friday evening activity becomes more isolated so have transitioned the mention of showers and storms to vicinity. Development of MVFR cigs is possible early Saturday morning.



PRELIMINARY POINT TEMPS/POPS
Chattanooga Airport, TN 81 65 79 64 / 50 50 70 40 Knoxville McGhee Tyson Airport, TN 77 63 78 63 / 70 50 80 50 Oak Ridge, TN 77 63 78 62 / 80 50 80 50 Tri Cities Airport, TN 77 61 76 60 / 60 50 80 60

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

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