Area Forecast Discussion
Issued by NWS Little Rock, AR

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000
FXUS64 KLZK 211139 AAA
AFDLZK

Area Forecast Discussion...Update
National Weather Service Little Rock AR
640 AM CDT Sat Oct 21 2017

.AVIATION...

Overall VFR flight conditions with some ceilings are forecast to
start the period. Early morning patchy MVFR cloud conditions will be
possible but coverage will be limited. After sunrise on Saturday,
any MVFR conditions will gradually lift to VFR. Light showers will
be seen this morning, and then increasing chances of convection will
be seen later on Saturday as a storm system approaches AR from the
northwest. Winds will be south to southeast at 5 to 15 mph with some
gusts to 15 to 20 mph. A low level jet has set up over west to
central AR this morning, and low level wind shear may be seen.
(59)

&&

.Prev Discussion.../ Issued 319 AM CDT Sat Oct 21 2017/

Main concerns in this forecast cycle are convection chances and
severe storm threat with the storm system as it moves through the
region this weekend and into Monday. Also any localized flash
flooding with potential isolated heavy rain.

Currently a south wind flow continues to increase moisture levels
into AR, with the surface high pressure to the east of AR.
Current dew point temperatures are in the mid 50s north to lower
60s over the south. 00Z KLZK sounding had a precip water value of
0.86 inches. Sounding also indicated some veering in the lower
atmosphere, with a low level jet around 2k-4k feet from the
southwest at 30-35 knots. An inversion was noted at 3500 feet.
Surface temperatures were in the upper 50s to mid 60s. Aloft the
upper high pressure ridge was over the southeast U.S., with a
trough to the east of AR. An upper southwest flow was now over
the region, which will allow the upper system to move toward AR
today, and some shortwave energy to also move through the region
and develop isolated to scattered convection.

&&

.SHORT TERM...Today Through Sunday Night

Overall convection chances today will remain on the lower chance
category, with some shortwave energy seen in the upper southwest
flow to move through the region. The highest will be possible over
far western AR. Plenty of cloud cover today will keep temperatures
in the upper 70s to lower 80s. Mainly showers this morning, then
showers and isolated thunderstorms this afternoon with a bit more
instability showing up. This evening through midnight, the main
core of instability, lift and moisture focuses over OK, where SPC
has the enhanced risk of severe storms, while slight to marginal
to the east into AR. Analysis of factors shows the main threat is
damaging winds as the line of storms forms along the main lift
core. Large hail a lower risk. Some veering in the profile is
seen, and an isolated tornado threat will be present, especially
with any individual storm or along any bowing line segment. More
likely embedded within the line of storms where mesocyclone
develop may occur. Also, localized heavy rain may be seen as
precip water values reach over one inch, especially along the
line, and a localized flash flood potential may develop. Although,
overall ground moisture levels are low going into the event.

Timing of the main storms for AR will be around midnight into the
NW, then overnight as the line of strong to isolated severe storms
move east. Models do show some gradual weakening of the dynamics
as the line moves east. Around sunrise on Sunday, the main line
will be very close to LIT. The line will continue to gradually
move east through the day Sunday as the cold front and upper low
pressure trough move through the region. Sunday evening to night,
the main line of storms will push out of AR, with lighter
convection on the back side. Models continue to show the possible
formation of an upper cut off low pressure system over northeast
TX, and forecast will keep some rain into Monday.

&&

.LONG TERM...Monday Through Friday

The cold front will be east of the state at the start of the long
term period...with a closed upper low situated mainly over AR early
on Mon. Some of the near/med-range model guidance has suggested some
lingering precip on Mon for ERN sections of the CWA...but should see
all precip move east of the state by Mon night and especially Tue as
the upper low exits the region to the east.

A new...deepening upper trough will dive SE across the Plains late
Mon into Tue...with a new cold front moving south through the state.
This will bring another shot of cool...dry air to AR for Tue through
Thu of next week. Expect dry conditions...and there may be some of
the coldest temps of the season so far expected for lows by mid
week.

SRLY flow will return by Thu...with temps rebounding. However...this
will be short lived as yet another...even stronger cold front will
move into AR by the end of the forecast. There are some
uncertainties this far out regarding timing of this front...so have
only mentioned slight chance to low end chance POPs Fri for now.
Temps behind this front look to be even colder than the mid week
front...but again uncertainty remains in timing and overall strength
of the overall storm system.

&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     78  65  68  51 /  20  90  90  30
Camden AR         81  68  70  53 /  30  80  80  30
Harrison AR       74  56  61  45 /  20 100  60  10
Hot Springs AR    77  66  68  52 /  30  90  70  30
Little Rock   AR  79  68  70  54 /  20  80  80  40
Monticello AR     83  69  72  55 /  30  50  90  60
Mount Ida AR      77  63  66  48 /  30  90  70  20
Mountain Home AR  76  60  64  48 /  20 100  70  20
Newport AR        79  66  70  52 /  20  80  90  40
Pine Bluff AR     82  69  73  54 /  20  70  80  40
Russellville AR   76  64  67  49 /  20  90  70  20
Searcy AR         79  68  70  51 /  20  80  90  40
Stuttgart AR      82  69  71  53 /  20  70  90  40
&&

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

$$

Short Term...59 / Long Term...62


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