Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 172022
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
322 PM CDT Sat Jun 17 2017

.SHORT TERM...Tonight Through Monday

Surface observations and visible satellite imagery show a frontal
boundary in place across northern Kansas and Missouri with
temperatures in the upper 80s and dew point values in the lower to
mid 70s south of the front. There were also remnants from a now
decayed linear MCS that moved south across eastern Oklahoma this
morning in place along the Oklahoma/Arkansas border. A large
cirrus shield was observed over this area which helped keep
temperatures down 5-10 degrees below what was forecast for today.
There may be some remnant circulation/MCV within these clouds, but
it was not evident from analysis of GOES 16 channels or surface
observations.

As a result...think that the cirrus shield keeping temperatures
down a few degrees will be enough to prevent afternoon showers and
storms from redeveloping over western Arkansas. Over the
southeastern portion of the state...an outflow boundary was
evident along the Arkansas/Louisiana border and surface based
cumulus was observed north and south of this boundary. Aside from
the stalled out boundary...there was no obvious lifting mechanism
in place...so only went with a 20 POP in the forecast southeast of
Pine Bluff to account for an isolated thunderstorm developing
before sunset.

For tonight...the frontal boundary up in northern Kansas and
Missouri is likely to see convection initiation within the next
couple of hours. Aside from frontogenetic forcing for ascent
associated with the front...water vapor satellite imagery showed a
compact but strong shortwave trough moving southeast towards the
KS/MO border this afternoon. This additional lift should be enough
to cause several updrafts to develop along the front in northeast
Kansas, likely growing upscale into a linear MCS or QLCS before
sunset. This MCS is expected to move southeast overnight
approaching the MO/AR border around 3 AM.

The shortwave trough is expected to move east-northeast overnight
resulting in the strongest upper level flow remaining well north
of Arkansas. As the linear MCS sinks south overnight it will
encounter increasingly weak deep layer shear. This fact coupled
with diurnal stabilization of the boundary layer favors a
weakening MCS structure as it moves south/southeast into Arkansas.
As a result think that the threat for severe weather across
northern Arkansas is dampened a bit and will only highlight low-
end damaging wind threat at this time.

While wind shear will weaken as the MCS sinks south...available
moisture and mid-level instability will remain plentiful...so the
MCS is very unlikely to completely dissipate before reaching the
state. As a result confidence is actually quite high regarding the
chance of storms entering the state early Sunday morning, but
quite low regarding how strong those storms will be as they
approach. Will have to monitor this system closely as it evolves
this evening and may have to update the forecast to increase the
severe storm threat if the outflow doesn`t tilt the updrafts as
severely as expected as the system enters the more weakly sheared
environment in place over the state.

Storms are expected to weaken significantly by sunrise on
Sunday/Father`s Day and should be approaching central Arkansas by
that time. The associated outflow boundary will likely continue
moving south as showers and thunderstorms continue to weaken or
dissipate as the boundary continues to move south. The boundary
may continue on towards the Louisiana border nearly rain free
late Sunday morning. Showers and thunderstorms are expected to
redevelop across the state by Sunday late morning/early afternoon
as the synoptic cold front arrives and provides strong forcing for
ascent. The cold front is expected to be somewhat slow moving and
assuming early morning outflow outpaces convection...this should
stabilize the environment a little bit for Sunday afternoon. With
slightly less available energy for storms, and with the stronger
upper flow remaining north of the state, think that most
thunderstorm activity along the cold front on Sunday will be sub-
severe. Strong to severe storms remain possible, with the primary
threat likely to be damaging winds from collapsing storms.
Organized and widespread severe weather looks unlikely.

Having a cold front move across the state in June does lead to
high confidence in storms though...and scattered to numerous
storms are expected along the front in central and southern
Arkansas Sunday afternoon and evening as a result. Went ahead with
widespread 50-60 POPs during this time across central and southern
Arkansas as a result. The front is expected to slowly sink south
Sunday night bringing the best rain chances south across southern
Arkansas Sunday night into early Monday morning. By late Monday
morning showers and storms are expected to move south with the
front into northern Louisiana.

Significantly drier air will move across the state behind the
front. This will make for a very pleasant day across Arkansas on
Monday with highs in the mid to upper 80s but with low humidity
for a change!

Cavanaugh

&&

.LONG TERM...Monday Night Through Friday

A ridge of high pressure over the southwest United States will
gradually build over Arkansas. This will result in mostly dry
conditions, and a slow warming trend.

Overall, conditions will not be oppressive given fairly
dry air in place/dewpoints in the 60s to around 70 degrees.
This will result in heat index values below triple digits.

Temperatures will start off near seasonal on Tuesday, and
will go a little above average in the days to follow. Again,
this does not appear overly hot.

Toward the end of the week, the ridge may actually retrograde
a bit. This will allow a front to slowly approach from the
north. Included isolated to scattered showers and thunderstorms
by the beginning of next weekend.

46

&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     74  83  65  85 /  30  60  40  10
Camden AR         76  89  72  88 /  10  30  60  30
Harrison AR       70  78  61  82 /  60  50  10   0
Hot Springs AR    76  86  70  88 /  10  60  60  20
Little Rock   AR  76  87  70  87 /  10  60  60  10
Monticello AR     76  89  73  85 /  10  30  60  40
Mount Ida AR      75  86  66  87 /  10  50  50  10
Mountain Home AR  71  80  62  85 /  60  50  20   0
Newport AR        74  84  67  86 /  30  60  50  10
Pine Bluff AR     76  89  71  86 /  10  50  70  20
Russellville AR   75  83  67  87 /  20  50  40  10
Searcy AR         74  85  68  86 /  20  60  60  10
Stuttgart AR      75  88  70  87 /  10  60  70  20
&&

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

$$

Short Term...CAVANAUGH / Long Term...46



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