120
FXUS64 KMRX 120236
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1036 PM EDT Sat May 11 2024

...New UPDATE...

.UPDATE...
Issued at 1025 PM EDT Sat May 11 2024

Forecast remains in pretty good shape this evening. Light,
isolated rain showers have diminished along with clearing skies.
Made some minor adjustment to hourly T/Tds as well as fog in the
weather grids. Most recent surface and satellite observations show
some light fog already developing in areas of far northeast
Tennessee and southwest Virginia that observed light precip this
evening. However, relatively drier air is filtering into the
region as the surface cold front has shifted across the forecast
area. Picking apart fog tonight is a tight balance of favorable
radiational cooling, decreasing dewpoints, and previous light
rain. Believe any fog throughout most of the central and southern
valley will be restricted to bodies of water as mentioned with
the afternoon package. The best chance for fog to potentially
spill out of river valleys will be in far northeast Tennessee and
southwest Virgina.

&&

.SHORT TERM...
(This evening through Sunday)
Issued at 155 PM EDT Sat May 11 2024

Key Messages:

1. Isolated to scattered showers are expected late this afternoon
into the evening hours.

2. Pleasant weather expected for the Mother`s Day holiday.

Discussion:

In the upper levels, northwesterly flow is in place with a ridge
building into the region tomorrow. At the surface, a cold front is
currently over Central Kentucky, starting to move into Middle
Tennessee. This front will move through the region this evening.
With a fairly dry air mass at the surface, showers ahead of the
front will be spotty with the best chance for a shower in SW
Virginia and NE Tennessee in the late afternoon hours and into the
evening. Thunder potential is low but a few strikes cannot be
ruled out.

Tonight, expect clearing skies after midnight allowing lows to get
down into the 40s by morning. Some fog development will be
possible mainly near bodies of water. Sunday will be dry with
highs mainly in the 70s with high pressure over the Southeast.

&&

.LONG TERM...
(Sunday night through next Saturday)
Issued at 155 PM EDT Sat May 11 2024

Key Message:

An active start to the work week, with rain and thunderstorm chances
through at least Wednesday. Another system looks likely at the end
of the week.

Discussion:

Monday will bring about a change in the synoptic pattern as the
ridging over the region is slowly overtaken by a slow moving
low/trough moving out of the southern plains towards the Ohio
Valley. We`ll see increasing Gulf moisture ahead of the system with
rain moving into the southern Valley in the morning hours, and
spreading northward the rest of the day. Expect morning
precipitation to most likely just be showers, but once we get into
the afternoon/evening hours we should start to see some thunder
thrown into the mix in some locations that are able to get a bit of
sun breaking through the cloud deck. On Tuesday we should see
greater coverage of precipitation and more thunderstorms as the
upper level low looks to track right through the Ohio/Tennessee
Valley, getting additional support from the in the right rear region
of the upper level jet. Tuesday could see some strong storms, but
the more likely threat will be from possible flooding with the
additional storms bringing locally heavy downpours.

Current forecast is showing generally around 0.5-1.5 inch rainfall
totals for Monday into early Wednesday, however with the more
isolated to scattered nature of the convection we can expect some
places to see more than 1.5 inches. Combine this with the fact that
river/stream levels may still be elevated from the rainfall earlier
this week and we could see re-aggravation of flood prone areas. Am
still in agreement with the WPC Marginal risk outlook for
Tuesday/Wednesday in the southern Appalachian Region.

We`ll get a bit of a break during Wednesday evening as the slow
moving system finally departs east of the Appalachian Mountains and
we`ll hopefully see mostly clear skies into Thursday ahead of the
next system.

That next system looks to be a much faster moving trough expected to
zip through the eastern half of the United States Friday and/or
Saturday. Still some disagreement in the deterministic models with
the timing and northern/southern extent of this system, but at this
time it looks likely that the end of the work week and start the
weekend with another wet and stormy period.

&&

.AVIATION...
(00Z TAFS)
Issued at 739 PM EDT Sat May 11 2024

Isolated showers continue to shift across our northern half. Have
kept a similar format with vcsh at TYS and shra at TRI for the
next two hours. Fog potential is possible overnight but given the
dry airmass in place this seems most favorable along and near
bodies of water. Have only included reduced vis at TRI. Quiet
weather continues tomorrow, though W to NW winds are expected to
gust near 20kts at TRI during the afternoon. Light winds 10kts or
less expected at TYS and CHA.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             53  81  58  72 /  10   0   0  60
Knoxville McGhee Tyson Airport, TN  49  76  54  74 /  20   0   0  40
Oak Ridge, TN                       48  77  54  73 /  10   0   0  40
Tri Cities Airport, TN              45  72  49  76 /  20   0   0  20

&&

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

$$

SHORT TERM...McD
AVIATION...KRS