Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 240536

Area Forecast Discussion
National Weather Service Little Rock AR
1236 AM CDT Sat Mar 24 2018


Mid level moisture will increase through the period as southerly
flow increases. VFR conditions initially will slowly deteriorate
to MVFR with a few isolated showers possible mainly across the
northern terminals. Winds will increase through the period as a
cold front moves into the state late in the period.


.PREV DISCUSSION...(ISSUED 652 PM CDT Fri Mar 23 2018)

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


Some MVFR CIGs are developing this evening at the NRN
terminals...but will likely see these spread further south
throughout the overnight hrs into the daytime on Sat. Some
occasional gusty SSW winds will be seen...with some spotty SHRA
also possible. A new front will drop SE into the state by the end
of this TAF period.


SHORT TERM...Tonight Through Sunday

Expect widely scattered, light precipitation across the northeast
half of the forecast area through late tonight, as isentropic lift
makes effort to overcome condensation pressures deficits across the
mid south.

A weak cold front will move through the state on Saturday. Weak
forcing and limited instability will prevent any widespread
convective activity.

This frontal boundary will stall, then will start to move northward
as a warm front on Sunday.  Somewhat greater coverage of convection
is expected with this feature, especially across western sections.

LONG TERM...Sunday Night Through Friday

At the start of the long term portion of the forecast period, a cold
front will be located south of the state and the flow aloft will
begin to transition to southwesterly. Some scattered showers will be
seen over the area as a weak disturbance traverses the flow.
Additionally, the much anticipated upper trough will have made its
way onshore from the west coast and begin to move further inland.

With upper ridging expected from the Gulf of Mexico northward to the
Northeast states, the upper trough will begin to slow its eastward
pace, deepen and likely close off south of the four corners region.
Ahead of this feature, abundant moisture will flow freely
northeastward from Texas to the Ohio Valley. 12z model data suggests
widespread PW`s of 1.25-1.50+ inches across Arkansas and nearby
areas. At the surface, a frontal boundary will be in place somewhere
over central to southern Arkansas. Enhanced lift aided by numerous
shortwave disturbances aloft as well as over the surface boundary
will aid in precip development over much of the state. With the
duration of this setup expected to last over a few days, several
inches of rain can be expected and another regional flooding threat
will develop.

Perhaps the latest takeaway from 12z mid-range model guidance would
be a possible gradual southeastward shift of the heaviest rainfall
axis. Initially, there was concern just west of the state, but the
latest information suggests that Arkansas will be firmly in the area
of concern as well as adjacent areas just to the south and east.

Lastly, rainfall should wrap up by early Friday morning, but I would
like to mention a few other things to consider. The primary upper
trough that will become the large storm system is still offshore and
hasn`t been sampled by CONUS RAOB sites yet. The location of the
surface and 850mb frontal boundary will help dictate the exact
location of heaviest rainfall next week and there is plenty of
uncertainty with the placement of these features. To counter the
aforementioned points regarding uncertainty going forward,
confidence in the overall setup aloft and moisture levels across the
area is very high and the heavy rainfall threat is very real next
week and shouldn`t be discounted.


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


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