Sunrise 6:35 AM   Sunset 8:28 PM Moonrise 4:32 AM   Moonset 6:06 PM

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FXUS64 KMRX 060740 AFDMRX

Area Forecast Discussion National Weather Service Morristown TN 340 AM EDT Mon May 6 2024

New SHORT TERM, LONG TERM

SHORT TERM
(Today and tonight)
Issued at 333 AM EDT Mon May 6 2024

Key Messages:

1. Scattered showers and thunderstorms today with an upper-level shortwave across the area.

2. Drier tonight as shortwave ridging builds in across the region and a stronger system approaches from the west.

Discussion:

Model guidance and WV satellite imagery this morning shows shortwave troughing across the Mid-Mississippi Valley, and this unsettled weather will move eastward through the day. By this afternoon, the upper-level trough is forecast to be over our region with widespread scattered shower and thunderstorm activity.
There is a low probability of some stronger thunderstorms this afternoon as the RAP shows MLCAPE around 2000 J/Kg; however, limited bulk shear will limit overall storm organization and mitigate the severe weather risk.

By tonight, shortwave ridging builds in from the west with drier and clearing conditions. Fog will be possible if cloud cover can significantly clear out as guidance suggests.

LONG TERM
(Tuesday through Monday)
Issued at 333 AM EDT Mon May 6 2024

Key Messages:

1. Scattered to numerous showers and storms are likely Tuesday into Tuesday night with a few strong to severe storms possible. Damaging winds and hail will be the main threats.

2. More organized storms are increasingly likely Wednesday evening into Wednesday night with all modes of severe weather possible.
Localized flooding will remain of concern to Thursday due to repeated storms.

3. Much cooler conditions return by Friday through the weekend with more limited rain chances.

Tuesday through Thursday

At the start of the period, an upper trough will be centered across the Northern Plains with a downstream jet extending to the upper Mississippi River Valley. A surface cold front will be located just west of Missouri/Arkansas. Across the southeastern U.S. up through the Ohio River Valley, a broad warm sector will be in place, along with deep moisture indicated by PWAT values of near 1.4 inches, i.e.
above the 90th percentile. During the day on Tuesday, some height falls are expected across the area as the upper-level features shift slightly eastward. Diurnal heating and large-scale ascent will be sufficient for scattered to numerous convection, especially in the afternoon through the evening hours. During the day, most sources suggest MLCAPE to peak in excess of 1,000 J/kg with deep-layer shear reaching 30 to 35 kts. As this is the first run of the CAMs, a great degree of uncertainty still exists with the timing and coverage of convection. However, this overall environment is supportive of better organization than all recent days. During the overnight hours, low-level winds and shear will increase, but this will also be when low-level instability decreases. A lot of the current model sources are suggesting more development overnight. As such, the main concerns will be damaging winds and hail, which is emphasized by mid- level lapse rates near 6 C/km and more organized storm structures.
The abundant moisture and repeated rainfall will also keep the localized flooding threat.

By Wednesday morning, a near 100-kt upper jet will extend into the southern Mississippi River Valley, which will enhance upper divergence via an indirect vertical circulation. Depending on the evolution of convection from the previous night, activity may continue through the morning. However, as the day goes on, dynamics will continue increase with the aforementioned cold front approaching from the west and 850mb flow exceeding 40 kts. Timing differences still exist, but most sources indicate convection to be ongoing to our west by the evening before moving in overnight. With respect to instability, the main question will be how much activity is ongoing through the day. With less activity, MLCAPE could be in excess of 1,500 J/kg with deep-layer shear above 40 kts and 0-1km shear of over 25 kts. In this scenario, all modes of severe weather would be of concern, notably above and beyond that of Tuesday. We are still at a temporal scale where CAMs will not reach into this event, but concern continues to increase for a more notable severe weather event Wednesday night into Thursday morning. This is further emphasized by the CIPS Analogs and ensemble probabilities of over 50 percent for Supercell Composite Parameter of over 5, especially along the Cumberland Plateau and southern Valley. By the day on Thursday, the cold front will likely reach the area with activity likely continuing through the day.

Friday through Sunday

By Friday, deep troughing will be over the area with much cooler conditions following the passage of the frontal boundary ahead of surface high pressure to the west. Still, weak ascent and remaining moisture will be sufficient for lower but continued PoPs. Large- scale troughing will persist into Saturday with high pressure arriving from the west but weakening in the process. This will make for cooler and drier conditions. Additional troughing into Sunday will keep cooler temperatures in place with low-end PoPs based on potential development of a weak system to our south.

AVIATION
(06Z TAFS)
Issued at 107 AM EDT Mon May 6 2024

Showers and thunderstorms increase in coverage this morning as an upper-level disturbance moves into our area with continued rounds of convection through Monday afternoon. Overall, VFR conditions will prevail with localized IFR conditions within any heavier showers and thunderstorms.

PRELIMINARY POINT TEMPS/POPS
Chattanooga Airport, TN 83 66 86 68 / 70 30 50 60 Knoxville McGhee Tyson Airport, TN 80 63 82 66 / 90 70 60 70 Oak Ridge, TN 79 63 83 66 / 90 70 70 60 Tri Cities Airport, TN 76 60 81 63 / 90 70 60 50

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

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