Flash Flooding and Hail in Arkansas, February 28, 2021

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
549 AM CST Sun Feb 28 2021

.AVIATION...Updated w/ a discussion for the 28/12Z TAFs

SCT -SHRA were noted over S/Wrn and N/Ern AR this AM. VIS have
improved significantly since the last fcst update w/ most
terminals at MVFR CIGs/VIS now...though some patchy fog may still
prevail through at least 15Z. More notably, a warm frnt was
positioned over S/Wrn AR, extending into the Nrn portion of the
state, and will continue to lift N/wrd through Sun morning.
Through the remainder of the morning, LLWS will remain prevalent
at all terminals, and have included appropriate SHR groups. Sun
afternoon, a cold frnt will enter from the N/W, bringing
widespread -SHRA/TSRA and a wind shift from Srly to N/Wrly.
-SHRA/TSRA will prevail along the frnt's movement, w/ settling wx
 and MVFR CIGs remaining behind the frnt later in the PD.

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&&

.PREV DISCUSSION...(ISSUED 329 AM CST Sun Feb 28 2021)
SHORT TERM...Today Through Monday Night

Latest radar imgry depicted a swath of intensifying convective cells
over the state with some weaker training shower development over
S/Wrn AR. IR Sat imgry would indicate these storms are becoming
stronger and more sfc based w/ cooling cloud top temps. QPE values
suggest a swath of 1/2" to 1" of rainfall has fallen from this
convection, with more in the forecast over the next 24 hours.

Sfc obs indicated a warm frnt was draped from S/W to N/E AR w/ foggy
conditions and reduced visibilities along the Nrn edge. Precip
activity appears to be following this bndry, but short term CAM
guidance is struggling to capture it. Given a moistening bndry layer
to the S of the frnt...e.g. Tds in the mid-60s over Srn AR, and
readings of upper 50s to low 60s as far as Cntrl AR, a transition to
sfc based convection is not out of the question and an uptick in
coverage could be possible through Sunday morning as the frnt
continues to advance N/wrd.

Through the day, a regime of WAA/moisture transport will cont over
the fcst area, w/ sfc temps in the low to mid 70s over the Srn half
of the state, and Td's in the low to mid 60s. Aloft, a positively
tilted trof axis will be positioned over the Four Corners region,
and broad swath of S/Wrly flow. Given a lack of any robust
shortwaves moving over the area, minimal cooling aloft/height falls
will help keep sfc based buoyancy more tame, however a plume of
MLCAPE b/w 1000-1500 J/kg will be in place over the state along the
I-30/I-40 split corridor.

Sun afternoon, a cold frnt will enter the state from the N/W. As
such, the bndry will encounter a rich moist bndry layer and
widespread thunderstorm activity is expected. Given bulk shear
values of 50+ kts, parallel to the sfc bndry, storm mode will lkly
consist of a linear segment to broken bands of cells. Nevertheless,
modest sfc to ML buoyancy and ample cloud layer shear will be
conducive for sustained updraft growth. Additionally, ample storm
relative helicity of 100-200 m2/s2 are progged over the warm sector,
and could enhance any sustained updrafts that do develop, promoting
a QLCS tornado threat. Given strong wind energy aloft and QLCS type
storm mode, strong and damaging winds will also be a hazard w/
afternoon/evening convection.

Lastly, given an anomalously moist bndry layer...e.g. PWATs over
1.5", well above the climatological 90th percentile...a flood risk
will be prevalent as well. Early morning convection will have
already primed portions of Cntrl and N/Ern AR w/ a swath of QPE
readings in excess of 1". QPF values for Sun afternoon/evening are
remaining steady in the 1" - 1.5" range, however there will be
potential for training along the frnt given parallel shear vectors,
and could promote localized regions of enhanced QPF, increasing the
flash flooding threat. 3 hr FFG remains modest over the S/Ern
portion of the state w/ most basins above 2"/3hrs, however small
pockets of <2"/3hrs remain, and could become compromised should
training occur...however confidence on where enhanced swaths of QPF
may fall remains lower at this time.

Sun night and Mon...The cold frnt will cont to progress through the
state, w/ precip cutting off quickly in the wake of the frnt, and
cooler and drier condns following up. Mon, rain chances will linger
over the Srn portion of the state as mrgl moisture remains invof the
aforementioned upper shortwave approaching the state.

LONG TERM...Tuesday Through Saturday

At the beginning of the period, an upper low will move through the
Red River Valley and into the mid south region. At the same time,
low pressure will form along a stalled boundary near the Gulf coast
will pass to the south. This will keep rain chances in the forecast
into Tuesday, but precip should end during the afternoon and
evening, as the upper low shifts into the Tennessee Valley and high
pressure moves into the region on zonal flow aloft.

By late in the week, the longwave pattern will amplify again, as
another system approaches from the Rockies. This will bring another
chance of rain.

Through the period, temperatures should stay within a few degrees of
climatological averages.

&&

.LZK Watches/Warnings/Advisories...
Flood Watch through late tonight FOR Arkansas-Bradley-Calhoun-
Cleveland-Desha-Drew-Jefferson-Lincoln-Lonoke-Monroe-Prairie-
Woodruff.

&&

Aviation...GREEN

Hazardous Weather Outlook
National Weather Service Little Rock AR
337 AM CST Sun Feb 28 2021

ARZ003>008-012>017-021>025-030>034-037>047-052>057-062>069-010945-
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-
337 AM CST Sun Feb 28 2021

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

.DAY ONE...Today and Tonight

Patchy fog will continue across the northern portion of the state
to the north of a warm front, however visibilities statewide
should improve by sunrise.

Scattered showers and thunderstorms will likely continue through the
early morning hours and into the early afternoon ahead of a cold
front advancing into northwest Arkansas. As the front enters the
state, widespread thunderstorm development is anticipated. Some
strong to severe storms are possible, with damaging wind gusts being
the primary concern. Severe storms will also be capable of producing
hail to one inch in diameter, primarily over southwestern portions
of Arkansas.

With winds over the state turning and increasing with height, a
couple of brief tornadoes can not be ruled out, especially during
the afternoon and early evening hours.

Heavy rainfall will accompany thunderstorm activity as well with
widespread rain accumulations of one to two inches and localized
heavier amounts. As such, a flooding risk will be prevalent over the
southeastern portion of the state Sunday afternoon through Monday
morning.

.DAYS TWO THROUGH SEVEN...Monday Through Saturday

Expect scattered showers to continue through Tuesday, with isolated
thunderstorms possible. Rain will once again affect the area late in
the week.

While isolated strong storms could occur in portions of the area,
widespread or organized severe weather is not expected at this time.

Due to heavy rainfall the last few days, as well as high soil
moisture content from snow melt, localized heavy rainfall will
continue to be a concern, especially over central and southern
Arkansas.

Continue to monitor the latest forecasts and statements from your
Arkansas NWS offices.

.Spotter Information Statement...

Spotter Activation May be needed.

&&

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

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