FXUS64 KMRX 050609 AAC
AFDMRX
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
109 AM EST Thu Dec 5 2024
...New AVIATION...
.UPDATE...
Issued at 921 PM EST Wed Dec 4 2024
Gusty winds are ongoing across the area ahead of an approaching
cold front. Winds will continue to gust between 20 and 30 mph
across valley locations through the night. Wind Advisory remains
in effect across the east TN mountains and portions of southwest
VA. Wind gusts up to 45 are expected, with isolated gusts up to 60
mph across the highest elevations such as Cove Mountain. As far
as forecast changes go, hourly temps were running several degrees
warmer than forecast due to the gusty southwest winds and
dewpoints several degrees lower. Made adjustments based on latest
obs. Temps are still expected to drop later tonight behind the
front, with gusty winds shifting from southwest to out of the
northwest as the cold air rushes into the area.
&&
.SHORT TERM...
(This evening through Thursday)
Issued at 315 PM EST Wed Dec 4 2024
Key Messages:
1. High winds possible tonight across the higher elevations, so
Wind Advisory in effect across east Tennessee mountains and added
three northern counties in Southwest Virginia.
2. Limited moisture with this front. Some orographic ascent will
produce light snow or flurries across the mountains.
3. Much colder airmass returns Thursday with falling temperatures
during the day.
Discussion:
A much warmer day today after some morning and early afternoon
cloud cover. Mid afternoon temperatures have still reached the
40s to lower 50s except where clouds held on across northeast TN
and southwest VA where after the cold start and lingering clouds
were only in the mid to upper 30s. Strong southwest winds were
bringing in a warmer airmass. Winds were still light in the
valleys of the northeast. For tonight a strong low pressure
system across the northern Great Lakes brings a cold front
southeast tonight and Thursday with very strong 850mb gradient
westerly winds around 50 kt. This will result in high winds
between 50 and 60 mph across higher elevations, a Wind Advisory
continues tonight through Thursday morning.
Still looks like limited moisture ahead of the front. The orographic
lift behind the cold front will produce light snow or flurries
across the mountains through Thursday morning. Accumulation
should only be a trace to a few tenths lower elevations and 0.5 to
around 2 inches highest elevations. The drier cold airmass should
clear the clouds out in the morning and be strong enough to drop
temperatures during the day Thursday.
&&
.LONG TERM...
(Thursday night through next Wednesday)
Issued at 258 PM EST Wed Dec 4 2024
Key Messages:
1. Well below normal temperatures through Saturday, followed by
a warm-up to above normal next week.
2. Dry through the weekend, with a wet pattern setting up for the
Monday through Wednesday time frame.
Discussion:
Surface high pressure will settle over the TN Valley on Friday,
bringing a very cold air mass to the region. 850 mb temperatures are
below the 10th percentile for this time of year compared against
Blacksburg sounding climatology. Clear and calm conditions on Friday
and Saturday mornings will be mainly in the teens for most of the
area, and Friday's highs will mostly be in the 30s. The 850 mb
thermal trough lifts away and allows for some warming on Saturday,
when highs will be in the 40s. A building ridge centered over the
Gulf of Mexico shifting to the Atlantic will bring warming
temperatures for early next week, with highs in the 50s to around 60
on Sunday and Monday.
Increasing moisture will accompany the shift of the ridge to the
Atlantic, and the approach of a trough over the Plains. An initial
shortwave trough will bring precip to the area on Monday, followed
by a deeper trough on Tuesday or Wednesday. Models appear to be
having difficulty and disagreements with the potential phasing of
the northern and southern stream, which will impact our rain
timing and amounts. While much of the details are uncertain, the
pattern favors a wet period with high PoPs. We could be looking at
total QPF amounts in the range of 1-2 inches for Monday through
Wednesday.
&&
.AVIATION...
(06Z TAFS)
Issued at 102 AM EST Thu Dec 5 2024
Gusty winds will be the main concern at TAF sites. Gusts of
20-30kt will continue at all sites through much of the period,
likely not dropping below 20kt gusts until the 21z-00z time frame.
MVFR CIGS will prevail at KCHA through daybreak or so, but
confidence in these conditions impacting KTYS and KTRI is less so
will just show a SCT deck in those locations. Lastly, SHRA
potential looks less likely as a general rule across the area
tonight. Relatively speaking KTRI has the best chance, but even
there confidence is low so have stuck with just a mention of VCSH.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 45 22 42 25 / 10 0 0 0
Knoxville McGhee Tyson Airport, TN 42 17 38 21 / 20 0 0 0
Oak Ridge, TN 40 16 38 21 / 10 0 0 0
Tri Cities Airport, TN 37 13 33 17 / 20 0 0 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 1 PM EST this afternoon for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
Monroe-Unicoi.
VA...Wind Advisory until 1 PM EST this afternoon for Russell-
Washington VA-Wise.
&&
$$
SHORT TERM...
LONG TERM....DGS
AVIATION...CD