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FXUS64 KMRX 101745 AFDMRX

Area Forecast Discussion National Weather Service Morristown TN 1245 PM EST Sun Dec 10 2023

New AVIATION

UPDATE
Issued at 1035 AM EST Sun Dec 10 2023

No big forecast updates through the rest of the day. The cold front is currently moving across the east TN valley and cold air will continue to push into the area through the day. Still expecting a transition from rain to snow across the highest elevations of the east TN mountains between 1 and 4 PM EST this afternoon. Only update to the forecast were hourly POP adjustments through the day to try and time the heaviest precip exiting to our east by this evening.

SHORT TERM
(Today and tonight)
Issued at 138 AM EST Sun Dec 10 2023

Key Messages:

1. Strong and gusty winds across the east TN mountains and foothills will continue through Sunday morning, Wind Advisory remains in effect.

2. Rain will continue this morning areawide. By this afternoon, rain will be east of the I-75 corridor.

3. Rain will change to snow late this afternoon and evening across our higher elevations. Minor snow accumulations expected across the east TN and VA mountains. 1 to 3 inches expected above 3500 feet.

Discussion:

The line of thunderstorms has weakened considerably and is almost out of the forecast area. The cold front is on our doorstep just west or near the Cumberland Plateau. Little movement has been noticed the past few hours. Frontal passage is expected around sunrise for much of the region but the trough is lagging behind and will not move through until this evening. Rain will continue behind the line becoming spotty showers or light rain through the morning hours. By afternoon, rain will be confined to the eastern half of the region east of I-75. After sunset, precip will be confined to the East TN mountains, possibly the NC counties, NE TN and SW VA as the trough finally passes.

A changeover to snow or rain/snow mix will begin in the higher elevations of the East TN and SW Virginia mountains late in the afternoon as temps plummet. After sunset, the lower elevations of NE Tennessee and SW Virginia will see some snowflakes as well but little to no accumulation is expected in this area as the moisture is quickly exiting by this time. Northwest flow will set in late this evening keeping the snowflakes falling in the higher elevations of East Tennessee and SW Virginia mountains, where total accumulation will be 1 to 3 inches mainly above 3500 feet.

A Wind Advisory remains in effect for the East Tennessee mountains and foothills through 9AM this morning. Gusts up to 55 mph can be expected in the highest mountain peaks and places prone to downslope wind enhancement. Elsewhere in the mountains and foothills, gusts around 40 mph will be possible. Depending on timing of the frontal passage and wind shift, the advisory may be dropped a couple of hours early.

LONG TERM
(Monday through Saturday)
Issued at 138 AM EST Sun Dec 10 2023

Key Messages:

1. Drier and colder on Monday with upper troughing and surface high pressure.

2. Moderating temperatures mid to late week with zonal flow aloft.

3. Another system may bring precipitation to the region next weekend, but uncertainty is high.

Discussion:

Upper troughing and surface high pressure will be across the region on Monday with clearing sky conditions and drier air across the region. Temperatures will be below normal across the Southern Appalachians.

The upper trough begins to lift on Tuesday with zonal flow aloft and southwesterly low-level flow returning to the region through mid- week. This will result in moderating temperatures with continued dry weather through the end of the week.

Big questions remain next weekend with poor run to run consistency from model guidance. A northern shortwave will dive southeastward across the Great Lakes and Ohio Valley with a southern stream system expected to develop near the Gulf Coast and move eastward. If these systems do not interact, we may remain mostly dry with minimal impacts for our region. This is what the new 0z guidance seems to indicate. Past guidance has been more favorable to some phasing of these two systems with a larger system that moves up the East Coast and brings precipitation to our region. For this reason, we will continue with 20 to 30 percent chance PoPs next weekend and continue to refine the forecast through the week.

AVIATION
(18Z TAFS)
Issued at 1239 PM EST Sun Dec 10 2023

Tricky forecast at CHA over the next few hours as they are straddling a MVFR/VFR cloud deck. VFR conditions anticipated over the next few hours, then remaining VFR through the period. North winds become gusty this afternoon at 18kts then settle late tonight. TYS should be mostly MVFR until late in the period with north winds 10kts or less. TRI will remain MVFR through the period with a west-northwest wind 10kts or less.

PRELIMINARY POINT TEMPS/POPS
Chattanooga Airport, TN 31 48 29 54 / 0 0 0 0 Knoxville McGhee Tyson Airport, TN 31 44 27 52 / 20 0 0 0 Oak Ridge, TN 29 46 26 51 / 10 0 0 0 Tri Cities Airport, TN 29 41 24 50 / 70 0 0 0

MRX WATCHES/WARNINGS/ADVISORIES
NC...NONE.
TN...Winter Weather Advisory from 4 PM this afternoon to noon EST Monday for Blount Smoky Mountains-Cocke Smoky Mountains- Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Unicoi.

VA...NONE.

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