Area Forecast Discussion
Issued by NWS Little Rock, AR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
827
FXUS64 KLZK 012049
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
249 PM CST Thu Dec 1 2016

.DISCUSSION...

Main concerns in this forecast period are over the weekend and
into next week with the chance of rain increasing over AR. Severe
storm threat at this time appears to be low and isolated, with
these rain events more rain and showers, versus thunderstorms. But
this will be monitored. Temperatures also will be chilly, and at
this time stay above freezing.

Sunny skies with cooler than normal temperatures are being seen
today. The surface high pressure had settled over the region,
and brought the dry and cool weather conditions. Highs were
reaching the 50s with some around 60 over the south. Light and
variable winds or light south to southwest winds are being seen.
The upper pattern has become more zonal, and this will help
systems move through the region over the weekend and into the
coming week.

&&

.SHORT TERM...Tonight Through Saturday Night

The short-term will have little weather, with mostly clear
tonight, and mostly sunny on Friday. Temperatures will be close to
a bit above normal values Friday. Increasing clouds will be seen
later Friday ahead of the next weather system. Rain chances are in
the forecast mostly after midnight in southwest AR, then spreading
across the state on Saturday and the weekend. As mentioned
earlier, instability will be low, and this event is more of a rain
and shower event and hence the forecast reflects this.
Temperatures over the weekend will be a bit cooler than normal due
to the cloud cover and rain. At this time, only far northern AR
will see some temperatures lowering to around 40 to the upper 30s
Saturday morning and Sunday morning, so have kept forecast liquid
at this time. This will be monitored while ground temperatures do
remain well above freezing. Rain amounts initially will be light,
then increase through the weekend.

&&

.LONG TERM...Sunday Through Wednesday...

Sunday...By Sunday morning the expectation is that the large upper
trough over the western CONUS has broken into two pieces. The
northern piece of energy aloft is expected to remain progressive and
continue east over the mid west while the southern piece of energy
cuts off into a closed low and moves slowly east towards the South
Plains. The northern piece of energy is expected to make its way
east of Missouri by early Sunday afternoon. Behind this trough upper
level shortwave ridging is expected to move over Arkansas out ahead
of the approaching closed low. This should cause widespread rain
showers to dissipate from northwest to southeast across Arkansas
throughout the day on Sunday. Kept some low chances of rain in the
forecast especially across southern Arkansas Sunday afternoon and
overnight because it is unclear how much the ridging will work
against the persistent lift from low-level warm air advection over
the state.

Monday...Upper level shortwave ridging and weak forcing for
subsidence will be replaced by strong forcing for ascent by late
Monday morning as the upper low weakens a bit...becomes negatively
tilted and moves northeast towards Arkansas. Low-level warm air
advection is expected to ramp up over the state Monday morning...
and then strong differential positive vorticity advection will
spread over the state Monday afternoon as the trough makes a move
directly at Arkansas.

The negative tilt of the upper trough (that is the cold air aloft is
forecast to become superimposed over warm air in the lower
troposphere) will help to steepen mid-level lapse rates over
Arkansas allowing for some isolated thunderstorm activity to develop
in the more widespread rain showers associated with the strong large
scale lift over the region out ahead of the upper trough. Severe
storms are not expected across Greater Arkansas at this time as it
looks like low-level moisture surge resulting in surface based
convection will remain shunted to the southeast over Mississippi and
Alabama.

If the low-level triple point were to back up more than currently
advertised into Arkansas...then the threat for severe storms would
increase substantially near and southeast of the triple point from
late Monday afternoon through Monday night. Synopticly this
system looks supportive of a high impact severe weather
event...but fortunately at this time it looks as though the
synoptic set up favors MS/AL over Arkansas. Will obviously keep a
close eye on the evolution of this system in later forecast in
case something changes.

Showers and thunderstorms will transition over to light rain showers
behind the upper trough Monday night through Tuesday morning. At
this time it looks like arctic air remains bottled up in the
northern plains long enough to prevent any chance of snow or frozen
precipitation Monday night and Tuesday across Arkansas. The
subsidence associated with strong cold air advection behind the
upper trough is expected to be enough to cause precipitation to come
to an end across the state by Tuesday morning.

The GFS now indicates that the strong cold air advection behind the
upper trough on Tuesday is sufficient to bring an end to rain
chances through the remainder of the week. However this seems to be
related to the speed of a much larger trough that is expected to
move east over the northern half of the CONUS behind Monday`s
passage of the negatively tilted upper trough over Arkansas. The GFS
keeps the trough farther north and moves it east faster than what
the ECMWF was advertising on its 01/00Z run. A slower and farther
south track to this second but much larger upper trough would
certainly lead to additional rain chances across Arkansas for
Wednesday into Wednesday night. Due to the discrepancy in the models
kept rain chances in the forecast for Wednesday and Wednesday
night...but lowered POPs to 20-30 percent as confidence in the large
scale mid-week model solutions is low at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     34  58  38  46 /   0   0  20  60
Camden AR         34  63  43  48 /   0   0  60  90
Harrison AR       34  57  36  46 /   0   0  20  60
Hot Springs AR    35  60  42  48 /   0   0  40  80
Little Rock   AR  36  61  41  48 /   0   0  30  80
Monticello AR     35  63  43  49 /   0   0  40  80
Mount Ida AR      34  60  41  47 /   0   0  50  80
Mountain Home AR  32  57  36  46 /   0   0  20  50
Newport AR        34  58  38  47 /   0   0  10  60
Pine Bluff AR     35  61  42  48 /   0   0  30  80
Russellville AR   34  59  41  46 /   0   0  40  70
Searcy AR         34  59  39  47 /   0   0  20  70
Stuttgart AR      35  61  41  48 /   0   0  30  80
&&

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

$$

Short Term...59 / Long Term...CAVANAUGH



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.