River Flood Advisory 20, NWS Little Rock, AR

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
557 PM CDT Mon May 3 2021

.DISCUSSION...

Updated to include the 00Z aviation discussion below...

&&

.AVIATION...

While VFR conditions are ongoing early this evening...SHRA/TSRA
will develop the west...and move NE into NWRN sections of the
state this evening...spreading further east and south overnight.
Expect condtions as low as IFR or briefly lower...especially
under the most intense activity. Some SVR storms could be
seen...with damaging winds and large hail. The strongest storm
activity will shift SE by sunrise Tue...though additional
SHRA/TSRA will remain possible into the early afternoon hrs Tue.
Expect improving conditions by late in this TAF period as drier
air moves into the state.

&&

.PREV DISCUSSION...(ISSUED 304 PM CDT Mon May 3 2021)

SHORT TERM...Tonight Through Wednesday Night

..TODAY AND TONIGHT...

Recent MSAS data, sfc obs, and subjective
analysis indicated a region of cyclonic sfc flow over Nrn TX/Srn OK,
w/ the the nose of this lower pressure beginning to nose into N/Ern
OK/Wrn AR. On a larger scale, a broad trof of lower pressure
extended from S/Wrn TX towards the N/E over the Ozark Plateau and
into the Upper Midwest. Turbulent bndry layer conditions have given
way to substantial mixing and morning low stratus has since mixed
out w/ an expansive diurnal Cu field beginning over Ern OK and more
recently portions of Srn AR. A strong pres grad was noted over the
state, and is continuing to drive strong Srly flow w/ temps in the
low to mid 80s currently over much of Srn AR, and upper 70s along
and north of the I-40 corridor. Td's in the lower 70s were noted
across Srn AR as well, w/ moisture transport expected to remain
rampant through the remainder of the afternoon as the aforementioned
sfc low approaches. The LZK 19Z sounding revealed a rather unstable
environment present over Cntrl AR w/ minimal CINH in place and steep
lapse rates contributing ML buoyancy in excess of 2000 J/kg.
To the N/W, a cold frnt was draped over KS and N/Wrn OK extending
into the Panhandle, and wl serve as the primary forcing mechanism
for CI later Mon night.

Over Mon night, several low amplitude perturbations wl traverse
through mean H500 S/Wrly flow on the downstream portion of a larger
impulse. This upper forcing wl overspread the region late in the
night and help aid in supplying some modest bulk shear, supportive
of sustaining organized convective activity. Latest thinking remains
consistent w/ this fcst update on the potential for a nocturnal
thunderstorm complex/MCS to develop over Ern OK and advance Ewrd
into portions of Nrn and Cntrl AR. Most recent suite of CAM and HREF
guidance is supportive of this fcst as well, w/ a NP bullseye for
strong winds over the Nrn portion of the state. Initially, a
multicell storm mode is anticipated following CI in Ern OK along the
advancing cold frnt, however weaker shear values and poor shear
vectors relative to the bndry wl contribute to interacting cold
pools and consolidation, leading to quick upscale growth into a
linear segment/MCS. Based on timing of probabilistic HREF guidance,
this segment should enter the Wrn portion of the state b/w the 02-
03Z timeframe. Due to the timing of the event, diurnal cooling may
begin to inhibit sfc based buoyancy playing a role in E/wrd
progression of the line, however pt fcst soundings are still
suggesting sufficient ML buoyancy around 2000-3000 J/kg w/ minimal
CINH. Thus initially, as the line enters the state, it wl encounter
a favorable environment to continue advancing E/wrd initially.
However as the night progresses, cooling wl lkly diminish remaining
buoyancy further E into the state and cause the line to weaken
eventually before 12Z.

Given the anticipated storm mode and HREF
progs, strong to damaging winds wl lkly be the primary hazards
associated w/ this system, however some large hail cannot be ruled
out in the early phases of storm development. Low-lvl shear progs
are not very supportive for QLCS tornadic activity, however it
remains non-zero at this time and cannot be ruled out either.

..TUES AND WED...

Tues, the aforementioned cold frnt wl sag S/Ewrd across the state w/
N/Wrly winds beginning to filter in drier air over the FA by the
later afternoon and evening. PoPs wl remain over much of the region
through the day w/ the FROPA and primary upper impulse lifting
N/Ewrd, however most can expect RH values and the general mugginess
begin to subside from N/W to S/E through the later evening, as Cntrl
Plains high pressure begins to sag S/wrd.

Wed, sfc high pressure wl begin to overtake the FA w/ Nrly winds
continuing to usher drier air in and promote a more settled wx
pattern with more seasonal temperatures resuming.

LONG TERM...Thursday Through Monday

A large area of high pressure will build over Arkansas from the
Plains, and that will bring a few days of dry conditions and below
average temperatures.

The high will depart by the weekend, and return flow will bring
temperatures back up to seasonal levels. At the same time, a new
storm system in the central Plains will drag a cold front toward
Arkansas, and rain chances will increase.

Scattered to numerous showers and thunderstorms are in the forecast
Saturday through Monday. At this time, the dynamics aloft to
support severe weather do not look impressive, so severe weather
should be localized. However, the front will be nearly parallel a
southwest wind flow aloft, and will be slow to cross the state.
That could lead to areas of heavy rain.

&&

.LZK Watches/Warnings/Advisories...NONE.
&&

Aviation...62

Hazardous Weather Outlook...UPDATED
National Weather Service Little Rock AR
300 PM CDT Mon May 3 2021

ARZ003>008-012>017-021>025-030>034-037>047-052>057-062>069-041000-
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-
300 PM CDT Mon May 3 2021

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

.DAY ONE...This afternoon and Tonight

Another round of severe weather is possible over the region
late this evening through Tuesday morning. The latest data indicates
that a complex of thunderstorms will likely track across the
state, posing a threat for large hail early in the overnight
period, with the primary hazard transitioning to damaging winds
which will last into early Tuesday morning.

Additionally, there could be some locally heavy rainfall, which
could lead to flash flooding and aggravate existing flooding
issues along some area rivers.

.DAYS TWO THROUGH SEVEN...Tuesday Through Sunday

Thunderstorms return to the forecast for the upcoming weekend.
Severe weather chances appear low at this time, but locally heavy
rainfall may develop.

.Spotter Information Statement...

Spotter activation may be needed tonight.

&&

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

44/67/56