FXUS64 KLZK 200004 AAA
Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
704 PM CDT Sun Aug 19 2018
Updated to include the 00Z aviation discussion below...
SHRA/TSRA will move across the state through this evening and
overnight...with some MVFR or lower conditions expected with this
activity. Some patchy fog will be possible overnight...but SRLY
winds should limit widespread or dense fog. Some SHRA/TSRA will
remain possible through Mon as well...but winds will switch to the
SW and W by late in the afternoon hrs.
.PREV DISCUSSION...(ISSUED 325 PM CDT Sun Aug 19 2018)
SHORT TERM...Tonight Through Tuesday
Current VIS satellite imagery showed showers and thunderstorms
developing along a warm front that was slowly lifting north on
Sunday afternoon. Low level clouds were seen moving northwest
depicting a southeast flow in the lower levels, however aloft,
persistent northwest flow over the last couple weeks had backed to
the southwest in response to a surface low near central Kansas. SAT
imagery depicts well defined drying at all levels behind the cold
front across central KS/OK. Abundant moisture continued to advect
into AR from the Gulf of Mexico. Temperatures this afternoon were in
the 70s and 80s north of the front, to 80s and 90s south of the
front. Dew points are in the lower to middle 70s. Theta E gradient
was highest across central AR near and south of the boundary. In
this area, ML CAPE values were 2000 to 3000 J/kg with SB CAPE
approaching 4500 J/kg. PWATS were 2.0 to 2.1 inches along and south
of the warm front. 0-3km helicity values should increase through the
evening from less than 100 m2/s2 to 150-300 m2/s2 across central and
Convection is expected to develop across AR through the afternoon.
Given all the environmental conditions already in place, severe
storms may be a concern heading into this evening through tonight.
Strong damaging winds and large hail are the main threats, however
given winds turn with height near this low, an isolated tornado or
two can not be ruled out, mainly across the northwest portion of the
Meridional flow is expected to persist in the upper levels through
much of the period. Heading into Monday the upper low begins to lift
towards the northeast as it deepens. Across our area this upper low
will provide continued forcing for ascent across much of the CWA.
This forcing will remain in place, continuing rain chances, until
the front passes late Monday into Tuesday. Expect drier and
slightly cooler air to filter in behind this front.
LONG TERM...Tuesday Night Through Sunday
An upper ridge will be over Texas to begin the period with northwest
flow over Arkansas and up through the Midwest. The northwest flow
continues over the area through the period with several impulses
coming around the ridge.
The long term forecast will begin dry and slightly cooler with
surface high pressure over the area. The high moves off to the
northeast Thursday and will allow a weak system to move through the
northwest flow and bring a chance of showers and thunderstorms. Rain
chances will continue on Friday and Saturday then chances decrease
Sunday. High temperatures will be mainly in the 80s Wednesday
through Friday, then more widespread 90s return for next weekend.