textproduct: Morristown

SHORT TERM

(Today and tonight) Issued at 248 AM EST Thu Dec 26 2024

Key Message:

Another warm day in store today

Discussion:

Currently a few showers are moving in the warm sector south of a stationary boundary draped across the Ohio Valley. There are a few areas of slightly higher reflectivity moving through east Tennessee, but this is just likely to be clouds with no stations reporting precipitation anywhere in our region outside of western KY and southern AL. It's not impossible that a rogue drizzle occurs for 5 minutes at some point early this morning, but the chances are too low to mention in the forecast.

Once the sun rises we'll experience another warm day with temperatures similar to what we got to yesterday, and maybe even a degree or two warmer. Surface winds will remain generally out of the south today along with riding throughout the mid and upper levels of the atmosphere. Overnight temperatures are expected to be even warmer than this morning as increased clouds ahead of the next system helps limit radiational cooling overnight.

LONG TERM

(Friday through Wednesday) Issued at 248 AM EST Thu Dec 26 2024

Key Messages:

1. Warmer than normal temperatures will persist through the weekend and into early next week.

2. A wet pattern will be in place from Friday through at least Sunday morning.

3. With deep layer moisture advection, some flooding issues will be possible mainly Saturday through Sunday morning.

4. Gusty mountain wave enhanced winds for the usual higher elevations and foothills at times Friday through Saturday night.

Discussion:

This forecast period starts on Friday with ridging and high pressure over the East Coast. A negatively tilted shortwave will move from the Central Mississippi Valley into the Ohio Valley on Friday as a trough in the Central U.S. deepens. Rain chances will increase areawide by Friday afternoon with the highest chances south of I-40 and the Cumberland Plateau as the ridge holds to the east. Friday night widespread rain is expected as another shortwave takes the same route into the Ohio Valley. The wet pattern continues through Sunday morning as a slow moving trough approaches from the west on Saturday. This trough will pass and rain will start to clear out by Sunday afternoon.

A modest drop in dew points is expected by Monday but winds will remain southerly, so any frontal passage will be weak. Monday will be dry with weak high pressure at the surface and zonal flow aloft. On Tuesday, the trough train continues with another shortwave passage bringing rain chances but this looks like a fast mover. It looks like we will get a cold frontal passage with this system with a moderate drop in temps and dew points midweek but a big cold push is not expected.

Highs will be in the upper 50s and lower 60s through this weekend and into early next week in the Tennessee Valley. Normal highs for Chattanooga, Knoxville and Tri-Cities are 51, 49, 47 respectively. Forecast rainfall totals from Friday through Sunday have increased and are now two to four inches with the higher amounts south of I-40 and along the Cumberland Plateau. With deep layer moisture advection Friday and Saturday, the duration of high precipitable water values has increased and will be above one inch in that area all day Friday through Saturday night before dropping sharply Sunday morning. This is in the 90th percentile for this time of year, peaking near the daily max value (1.3 in) according to sounding climatology.

Flash flooding is starting to be more of a concern mainly for Saturday through Sunday morning. Drought conditions in the western and southern parts of the region (where the highest rain totals are expected) will help limit flooding potential but with rain totals of 2 to 4 inches over 2-3 days some flooding impacts will be possible especially low-lying and flood prone areas. We will continue to monitor flooding potential.

Mountain wave winds are possible Friday through Sunday. With a southerly or southeasterly wind direction, downslope wind enhancement is likely in the mountains and foothills. A Wind Advisory will likely be needed by Friday night.

AVIATION

(06Z TAFS) Issued at 1257 AM EST Thu Dec 26 2024

VFR conditions expected for the next 24 hours. Some extremely light radar returns are moving up through the Tennessee Valley currently. If one goes over an airport it could cause a brief round of drizzle, but chances are too low to mention in the TAFs.

PRELIMINARY POINT TEMPS/POPS

Chattanooga Airport, TN 57 46 54 49 / 0 10 70 90 Knoxville McGhee Tyson Airport, TN 58 41 61 52 / 0 10 60 80 Oak Ridge, TN 57 40 56 51 / 0 10 60 80 Tri Cities Airport, TN 57 37 59 49 / 0 10 40 70

MRX WATCHES/WARNINGS/ADVISORIES

NC...NONE. TN...NONE. VA...NONE.