Another high impact winter weather event struck much of north Alabama and southern middle Tennessee during the evening of the 18th into the early morning hours of the 19th. A strong frontal boundary remained nearly stationary along the spine of the Cumberland Plateau.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HUN wrote it up.
Another high impact winter weather event struck much of north Alabama and southern middle Tennessee during the evening of the 18th into the early morning hours of the 19th. A strong frontal boundary remained nearly stationary along the spine of the Cumberland Plateau. This divided temperatures above freezing in the upper 30s to upper 40s southeast of the front, mainly southeast of Winchester in southern middle Tennessee with temperatures in the upper 20s to around 30 northwest of the boundary. Another upper level impulse that produced widespread winter weather across much of the south central U.S. and western Gulf states moved into the region. This spread widespread precipitation northeast into southern middle Tennessee. Southeast of the freeze line, or from roughly Sewanee through southern Franklin County, the precipitation was rain for the duration of the event. In fact, moderate to locally heavy rainfall of 1-2 inches was received. Northwest of the freeze line, the precipitation began as light snow or ice pellets, but quickly intensified into moderate to heavy snow, with accumulation rates of 1-2 inches per hour. Snow accumulations reached 2-3 inches in Franklin and Moore Counties, and 3 to 6 inches in Lincoln County. The snow changed to freezing rain or rain before ending. This made for a slushy mess with road conditions deteriorating quickly over the area.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Huntsville, AL wrote its last area forecast discussion before the first event at Feb 17, 5:34 PM CST, 1 hour 26 minutes earlier.
Area Forecast Discussion
National Weather Service Huntsville AL
534 PM CST Wed Feb 17 2021
.UPDATE...
For 00Z TAFS.
&&
.NEAR TERM...(Remainder of today and tonight)
Issued at 305 PM CST Wed Feb 17 2021
Another rapidly evolving winter precipitation event is unfolding
across the local forecast area this afternoon, as strengthening
southwesterly flow and warm air advection above the shallow arctic
airmass (in place across the Lower MS Valley/Mid-South/TN Valley) has
resulted in a rapid increase in coverage and intensity of
precipitation to our southwest. This regime is expected to spread
rapidly east-northeastward across northern AL/southern TN for the
remainder of the afternoon, with widespread moderate-locally heavy
precipitation anticipated this evening, as the lower tropospheric
column up to the critical snow growth zone becomes entirely
saturated. Forecast soundings continue to indicate thermal profiles
sufficiently cold for snow as the predominant precipitation type, at
least at the onset of the event. However, over the course of the
evening, a deepening layer of warm air aloft (associated with a
strengthening southwesterly low-level jet) should lead to a
transition to sleet and eventually freezing rain. Fortunately, it
appears as if the axis of widespread moderate-locally heavy
precipitation will also be shifting eastward as this occurs, and
should exit our eastern zones by 10-11Z, if not a bit sooner. Thus,
only light freezing drizzle is anticipated to end the event early
Thursday morning (which would ultimately be light drizzle for
portions of Cullman/Marshall/Dekalb/Jackson counties, where surface
temps will likely remain above freezing).
Predicted snowfall totals did increase with this forecast update,
which is not surprising based on current reflectivity imagery from
the WSR-88D network and expectations that snow could become locally
heavy at times late this afternoon/early this evening. Much of the
current Winter Storm Warning area is now expected to receive between
4-5 inches of snow, and totals in this range may also occur across
northwestern Madison County and atop the Cumberland Plateau in
Franklin/Jackson counties (where temperatures remain below freezing
as of this writing). However, we will leave the current configuration
for the Winter Storm Warning and Winter Weather Advisory intact, as
warmer surface temperatures this afternoon may limit accumulations in
zones covered under the Advisory. Accumulations of freezing rain
will occur after snow has already fallen (and toward the end of the
event), and will generally range from 0.05-0.10 inch in the warning
area to between a trace and 0.05 inch elsewhere.
.SHORT TERM...(Thursday through Saturday)
Issued at 305 PM CST Wed Feb 17 2021
Global models suggest that the axis of the broad mid-level longwave
trough to our west will shift eastward across the central Plains and
into the MS Valley on Thursday/Thursday night. The trough will become
more amplified with time as a strong vort max digs through the base
of the trough across South TX, and this should maintain sufficient
synoptic scale ascent across the TN Valley for scattered patches of
light rain across the region throughout the day tomorrow. For
locations to the immediate north/west of the Huntsville metro area
where surface temperatures may hover around or just below freezing,
this would occur as freezing rain, but precipitation coverage will be
lower (compared to recent events) and the intensity of this
precipitation is expected to be rather light. Nonetheless, it could
create some additional impacts for locations that may receive up to
5 inches of snow later today. With the axis of the longwave trough
still to our west, the threat for spotty light freezing rain or snow
flurries will persist on Thursday night beneath a low stratus cloud
deck, as temperatures plunge into the upper teens (NW) and mid 20s
(SE). However, lingering precipitation will end and skies will begin
to clear from W-to-E by late Friday morning, as the trough axis
crosses the region, veering deep-layer flow to the northwest. A
surface ridge will build northeastward into the region on Friday
night and into the central Appalachians by Saturday, providing
light/variable winds. A gradual increase in high-level clouds
associated with a secondary vort max dropping from the MO Valley into
the Mid-South may inhibit ideal radiational cooling Friday night,
but lows should still drop into the mid/upper teens. Modest warming
will occur on Saturday, with mostly sunny skies promoting highs in
the l-m 40s.
.LONG TERM...(Saturday night through Tuesday)
Issued at 305 PM CST Wed Feb 17 2021
Clear skies and light winds, great conditions for radiational
cooling, will once again make for a chilly Saturday evening. Expect
temperatures to bottom out in the mid 20s by daybreak Sunday.
Overall, Sunday will be quite nice with temperatures finally getting
near their climatological normals in the mid 50s. Sunshine will be
plentiful for the first half of the day before clouds ahead of our
next system increase from the west by the afternoon. With a more
zonal upper air pattern compared to the earlier this week, the main
shortwave will be well to our north as it slides eastward across the
Midwest during the day Sunday. A cold front draped to the south of
this wave will arrive in the Tennessee Valley Sunday night bringing
area wide rain. Not a lot of moisture associated with this front and
combined with its fast movement, rainfall totals will be on the
lighter side.
Despite the cold front passing through overnight Sunday, the airmass
behind it really is not much colder. Longer range guidance suggests
a slight pattern shift to more seasonal temperatures and drier
conditions for Northern Alabama and Southern Middle Tennessee as we
head into the next week. In fact, a return to the 60s is not out of
the question by the end of the forecast period on Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 530 PM CST Wed Feb 17 2021
VFR conditions currently across the terminals but flight conditions
will be deteriorating quickly over the next hour or two. Snow and
sleet will begin shortly at MSL and by 01z at HSV. There is still
some question as to precipitation type but expect snow/sleet will be
the primary precipitation types. A mixture of snow/sleet could be
heavy at times in the 02-06z timeframe with visibilities down to
around 1/2 a mile. Ceilings will also drop to IFR as the
precipitation intensity increases. A strong low-level jet will warm
temperatures aloft and precipitation type may change to a mix of
freezing rain or rain after 06z. However, as this occurs, expect
precipitation intensity will be decreasing. IFR ceilings will persist
throughout the remainder of the TAF cycle. Precipitation will come
to an end around 10-11z. There is the possibility for light rain or
freezing rain during the day Thursday but not enough confidence in
this to include in the TAFs at this time.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Winter Weather Advisory until 6 AM CST Thursday for ALZ006-007-009-
016.
Winter Storm Warning until 6 AM CST Thursday for ALZ001>005.
TN...Winter Storm Warning until 6 AM CST Thursday for TNZ076-096-097.
&&
NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...GH
AVIATION...MA
For more information please visit our website
at weather.gov/huntsville.Hazardous Weather Outlook...UPDATED National Weather Service Huntsville AL 344 PM CST Wed Feb 17 2021 ALZ001>010-016-TNZ076-096-097-181130- Lauderdale-Colbert-Franklin AL-Lawrence-Limestone-Madison-Morgan- Marshall-Jackson-DeKalb-Cullman-Moore-Lincoln-Franklin TN- 344 PM CST Wed Feb 17 2021 This Hazardous Weather Outlook is for north Alabama and portions of southern middle Tennessee. .DAY ONE...Remainder of today and tonight... Snow will expand in coverage and intensity as it spreads eastward into the outlook area late this afternoon. A period of moderate to locally heavy snow is possible this evening, before precipitation transitions to sleet and freezing rain as it ends from west to east early Thursday morning. A Winter Storm Warning is in effect for all of northwest Alabama and southern Middle Tennessee through 6 AM CST Thursday, and a Winter Weather Advisory is in effect for portions of the region not covered under the Winter Storm Warning. Please consult these products for additional details. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday... Light precipitation will be possible on Thursday and Thursday night before ending late Friday morning. This could occur as light freezing rain for the northwest portion of the outlook area on Thursday, and a mixture of light freezing rain and snow flurries for all areas on Thursday night. .SPOTTER CALL TO ACTION STATEMENT... Activation of storm spotters and emergency management personnel is not anticipated at this time. 70/DD
The national radar mosaic for the moment the first event began.
3 winter storm. Local standard time, as filed.
Snowfall accumulated as much as 3.7 inches 3.9 miles W of Winchester. In Sewanee and Winchester, 3.0 inches were observed.
Snowfall accumulated as much as 3.5 inches 0.7 miles WNW of Lynchburg.
Snowfall accumulated from around 3 inches in southeast portions of the county to over 5 inches in western portions of the county. Observers 4.0 miles ENE of Frankewing and 8 miles WSW of Fayetteville observed 5.5 inches.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2021Every state in 2021This day in weather historyWarnings in Tennessee, February 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 942390, 942391, 942392.