Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 182323 AAA
AFDLZK

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
523 PM CST Sun Feb 18 2018

.AVIATION...
Conditions will vary between MVFR and IFR or lower. Southeast/
southerly winds of 8-12 knots sustained, with higher gusts
approaching 20 knots will be possible. Expect light showers
especially after dawn Monday in the north and west, as a cold
front approaches.
&&

.PREV DISCUSSION...(ISSUED 257 PM CST Sun Feb 18 2018)
SHORT TERM...Tonight Through Tuesday

Widespread cloud cover has been seen throughout the day across
most of Arkansas, with little hope in the coming days to see much
in the way of sunshine. Surface map this afternoon indicates high
pressure well east of the area, centered over the Mid-Atlantic
states. In the Central Plains, low pressure was noted and between
these two separate systems southeasterly winds were in place
locally.

Through the evening hours and continuing through the short term
portion of the forecast, the flow aloft will be out of the
southwest. This setup can be attributed to a persistent ridge in
place off the southeast Atlantic coast and large scale troughing
attempting to move from the Pacific NW into the central part of
the country. A series of weak disturbances will ride along the
flow and help trigger isolated to scattered showers/thunderstorms
across the state. Initially, and for much of this period, the
primary axis of moisture at the surface and through the mid levels
of the atmosphere will be focused across western Arkansas and
eastern Oklahoma.

By Tuesday, with the trough possibly making minor progress eastward
over the western US and a surface cold front approaching the
area, the concentration of greatest moisture and widespread precip
will ease further into the CWA. The focus for heavy rainfall will
begin across western Arkansas near the end of the short term
period with the greatest focus in the long term portion of the
forecast. A few other points of interest with the potential for
heavy rainfall: current dewpoint forecast values are in the 60s
all the way north to the Missouri border on Tuesday and a corridor
of PWAT values, based on 12z model guidance from east Texas into
northern Arkansas, may be in the ballpark of 1.5". If these PWAT
values are realized, they will exceed record values for Tuesday at
KLZK (records since 1948).

Other concerns during the short term portion of the forecast will be
some foggy conditions tonight into Monday morning. During the day
Monday and Tuesday, as the surface pressure gradient tightens ahead
of the approaching front, gusty southerly winds will be seen across
much of the state.

LONG TERM...Tuesday Night Through Sunday

Not much has changed in the extended period. It still looks very
unsettled, with periods of heavy/excessive rain.

The period will begin with a cold front sagging through the region
from the north. Shallow cold air behind the front will not give it
much push, and the front will be parallel to a persistent southwest
wind aloft. So, the front will takes its sweet time passing through
the area.

Well above average moisture will surround the front, and a swath of
heavy rain should be ongoing early Wednesday across the northwest
half of the state. Rain will build into the southeast counties with
the front Wednesday night/Thursday.

It appears the front will stall briefly along the Gulf Coast before
wobbling back to the north Friday/Saturday. That will result in more
widespread rain through next weekend.

Interestingly, little in the way of severe weather will be noted.
Also, it does not look cold enough behind the front for any wintry
precipitation. If that was to happen, it would be late Wednesday
night/early Thursday.

So, the main and ongoing story with this event will be the potential
of flash flooding and eventual river flooding. Four to six inches of
rain is in the forecast by the end of period. There could be locally
more than half a foot. Drought over the northern/western counties
may lessen high water problems a bit. But, runoff will be elevated
due to dormant vegetation/a lack of consumption of ground water.
In the end, this much rain will create high water issues no matter
how you slice it. That is, of course, if this much rain actually
materializes.

Temperatures will waver through the period. It will be a cool start
as the front drifts southward through the area. Late in the week, it
will be mild again as the front lifts toward the Missouri border.

&&

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

$$


Aviation...57



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