Tornadoes and Flash Flooding in Arkansas, January 10 to 11, 2020

Area Forecast Discussion
National Weather Service Little Rock AR
612 PM CST Fri Jan 10 2020

.AVIATION...11/00Z TAF CYCLE

For the 00Z TAFs, expect widespread MVFR conditions, rapidly
deteriorating to IFR after 11/00Z at all terminals. A progressive
line of RA/TSRA are expected to move from W to E through the fcst
area late Fri night through early Sat morning. Strong W/Nwrly
winds of 20 kts, with gusts up to 40 kts will be possible as the
line of storms moves through the state, with IFR VIS/CIGS
accompanying the line as well. Storms are expected to be clear of
AR late Sat morning, with SHRA remaining behind, and CIGS
improving to MVFR across Srn terminal sites through the end of the
period. In far N/Wrn AR, a wintry mix of precip including SN will
be possible, likely impacting Nrn terminals Sat after 16Z, and
tapering off by the end of the period.

&&

.PREV DISCUSSION...(ISSUED 235 PM CST Fri Jan 10 2020)
SHORT TERM...Today Through Sunday

It was a rainy start to the day across the Natural State with
showers and isolated thunderstorms persisting through the morning
hours. So far this afternoon, much of the state has seen a lull in
convection, with radar only showing widespread light rain showers.
However, to our west in Oklahoma, strong to severe thunderstorms
have initiated through the last few hours, and should continue
moving northeast into Arkansas through the evening and overnight
hours. Despite ongoing shower activity and overcast skies,
temperatures have warmed into the 60s and 70s statewide.
Additionally, moisture advection has increased dewpoint temperatures
across the state due to persistent deep southerly flow, which will
aid in precipitation chances through the next 24 hours.

Very strong southerly flow will continue across the region as an
intensifying vort max digs across the Southern Plains and heads
northeastward into Arkansas and Missouri. As the storm system
continues to approach the state, expect convection to increase
through the evening and afternoon hours. An associated cold front
will sweep eastward through Oklahoma and into Arkansas overnight and
early Saturday, with a line of strong to severe thunderstorms ahead
of it. This line of storms will pose a significant damaging wind
threat, with isolated tornadoes also possible. This is supported by
latest model guidance which suggests large amounts of wind shear (0-
1km SRH forecast to be around 300 to 400 m2/s2 and 0-3km SRH
forecast to near 400 to 500 m2/s2) and adequate instability (SBCAPE
around 500 to 1200 J/kg). Severe weather is especially likely across
the southern half of the state where convective parameters are the
most favorable. Additionally, any discrete convection ahead of the
main line expected tonight, could pose a hail threat.

Heavy rainfall is still expected with thunderstorms today and
tomorrow, resulting in the possibility of flash flooding and
worsened ongoing river flooding. Rich moisture moving into the
region from the south will help aid in high PWAT values near 1.5
to 1.8 inches through Saturday. Widespread rainfall amounts should
range from 2.5 to 3.5 inches, with higher isolated amounts up to
4 inches possible, especially across the western and central
portions of the state.

As the strong cold front mentioned above sweeps into the state on
Saturday, expect strong winds with gusts up to 30 to 40 mph
intermittently. Temperatures will also drop rapidly into the 30s and
40s by the late afternoon hours. This cause chances for wintry
precipitation as lingering rain showers transition gradually into
snow. Snowfall amounts should stay around an inch or less, and
primarily fall across the northwest half of the state. Impacts
should remain minor, however overpasses, bridges, and other elevated
surfaces could become slick. Trace amounts of ice are also possible
across the far northwest.

More tranquil weather will return on Sunday, with highs in the upper
40s and 50s and lows in the 20s and 30s.

LONG TERM...Sunday Night Through Friday

Long term periods will largely be controlled by lackluster longwave
flow (not flat, but not amplified). Several surface systems will
remain in the vicinity of the area, which will keep precipitation
chances elevated and temperatures within a few degrees of average
(mostly). Highest rain chances will come late in the period as upper
trough digs down into the plains, and a more potent surface system
pushes in. Could be some strong storms/heavy rain with this
particular system, but there's too much uncertainty this far out for
any specificity.

&&

.LZK Watches/Warnings/Advisories...
Flash Flood Watch through late tonight FOR Arkansas-Baxter-Boone-
Bradley-Calhoun-Clark-Cleburne-Cleveland-Conway-Dallas-Desha-
Drew-Faulkner-Fulton-Garland-Grant-Hot Spring-Independence-Izard-
Jackson-Jefferson-Johnson-Lawrence-Lincoln-Logan-Lonoke-Marion-
Monroe-Montgomery-Newton-Ouachita-Perry-Pike-Polk-Pope-Prairie-
Pulaski-Randolph-Saline-Scott-Searcy-Sharp-Stone-Van Buren-White-
Woodruff-Yell.

Wind Advisory from midnight tonight to noon CST Saturday FOR
Arkansas-Desha-Drew-Jackson-Lawrence-Monroe-Randolph-Woodruff.

&&

Aviation...GREEN

Hazardous Weather Outlook...Updated
National Weather Service Little Rock AR
745 AM CST Fri Jan 10 2020

ARZ003>008-012>017-021>025-030>034-037>047-052>057-062>069-111100-
Boone-Marion-Baxter-Fulton-Sharp-Randolph-Newton-Searcy-Stone-Izard-
Independence-Lawrence-Johnson-Pope-Van Buren-Cleburne-Jackson-Logan-
Conway-Faulkner-White-Woodruff-Scott-Yell-Perry-Polk-Montgomery-
Garland-Saline-Pulaski-Lonoke-Prairie-Monroe-Pike-Clark-Hot Spring-
Grant-Jefferson-Arkansas-Dallas-Cleveland-Lincoln-Desha-Ouachita-
Calhoun-Bradley-Drew-
745 AM CST Fri Jan 10 2020

This Hazardous Weather Outlook is for a Large Part of Arkansas.

.DAY ONE...Today and Tonight

Showers and isolated thunderstorms remain in the forecast today.
That will be followed by an outbreak of severe weather and a
significant heavy rain event tonight and through the early morning
hours Saturday.

A large storm system approaching from the southern Plains will be
responsible for the active pattern. Thunderstorms will begin
developing in eastern Oklahoma and eastern Texas by late this
afternoon, and will remain in place through the evening awaiting the
arrival of the system. Once the system nears, a line of storms will
kick to the east and move through Arkansas tonight.

The incoming line of storms will likely bring widespread severe
weather to the region. The main concern will be damaging winds, and
there may be a few tornadoes as well. Where wind damage occurs,
gusts may be hurricane force or higher.

Ahead of the line, some data is indicating scattered thunderstorms
in southwest Arkansas this evening. This will be monitored very
closely, as storms such as these will have the potential to
spawn tornadoes.

Storms overnight will produce torrential downpours. Two to more than
three inches of rain is expected to dump in much of the state. Given
that vegetation is dormant and not consuming much ground water,
downpours will runoff quickly, and this will increase the flash
flood potential.

This event will also feature windy conditions. South to southeast
winds at 10 to 20 mph today will increase to 20 to 30 mph tonight
before shifting to the northwest. Gusts could reach 40 mph in
portions of eastern Arkansas.

.DAYS TWO THROUGH SEVEN...Saturday Through Thursday

Precipitation will gradually taper off on Saturday as colder air
filters into Arkansas. Lingering light rain will change to light
snow in the Ozark Mountains of the northwest. Some spots could pick
up a half inch to an inch of snow, mainly on grassy areas. Roads
will remain wet, with icy patches possible Saturday night as
temperatures drop below freezing.

.Spotter Information Statement...

Spotter activation may be needed tonight and early Saturday.

&&

Visit NWS Little Rock on the web. Go to https://weather.gov/lzk.

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