Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 202003
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
303 PM CDT Fri Oct 20 2017

.SHORT TERM...Today Through Sunday Night

Early afternoon water vapor satellite imagery and 12Z subjective
RAOB analysis showed a large upper trough over the northwestern
CONUS and a shortwave trough located over the southern high
plains. A large upper level ridge was in place over the
southeastern CONUS...extending north over the Great Lakes region.
Regional radars showed isolated rain showers extending from east
Texas to the north over western Arkansas and into Missouri. Rain
was extremely light with only sprinkles making it down to the
surface as the rain showers were elevated over a very deep layer
of dry air as observed by the LZK morning weather balloon. The
southern high plains shortwave trough and retreating upper level
ridging were aiding in the moistening and cooling of the
thermodynamic profile aloft though and will help set the stage for
heavier rainfall Saturday night into Sunday.

For tonight...persistent warm and moist air advection will cause
clouds to increase throughout the overnight hours. The increase in
southerly winds near sunrise and return of low-level clouds on a
weak low-level jet will keep overnight temperatures warm and in
the lower to mid 60s for lows tonight/Saturday morning. The
increase in clouds will prevent temperatures from getting too warm
on Saturday...but some breaks in the clouds and filtered sunshine
will still allow temperatures to climb up into the mid to upper
70s by Saturday afternoon due to the warm start to the day. The
southern high plains shortwave trough is expected to move
northeast of Arkansas tonight. This will take some of the lift we
are seeing with today`s showers away from the region, likely
keeping most areas dry during the day on Saturday. However
persistent warm and moist air advection will keep at least some
weak lift in place over the state...so kept a 20 percent chance of
rain in the forecast to account for the potential for an isolated
shower or storm with the return of deeper moisture.

The large upper trough currently over the northwestern CONUS will
dig southeast during the day on Saturday. A strong shortwave
trough is expected to rotate through the base of the larger upper
trough and spread strong large scale forcing for ascent over
eastern Oklahoma and western Arkansas Saturday evening through the
overnight hours. This strong lift combined with deep southerly
flow will moisten up the troposphere resulting in deep moist
adiabatic lapse rates over the state and very little cap. This
will allow for very efficient precipitation processes resulting in
a very high confidence in most locations across the state seeing
thunderstorm activity Saturday night into Sunday morning. Have
anywhere from 80 to 100 POPs in the forecast from Saturday night
to Sunday as this upper level system moves over the area.

There is a chance for some severe storms Saturday night into
Sunday morning across northwestern Arkansas. With strong lift and
little cap to work with...convection should organize into a long
line or several clusters of storms in a line. Either way the storm
mode will favor a primary hazard of damaging straight line winds
and localized heavy rainfall and flooding. There is some small
threat for tornadoes but with the storm system primarily moving
through during the overnight hours...surface based instability
will be limited. Thunderstorm activity will continue across the
state on Sunday...but the threat for severe weather is expected to
remain low.

If the upper level system is slower than expected
similar to what the 12Z NAM shows...there may be a low threat of
severe storms across eastern Arkansas Sunday afternoon. If the
system is on pace with the 12Z GFS forecast then it looks likely
that low-level cold air will outpace the upper level cold air and
storms on Sunday will remain elevated keeping the severe weather
threat low. Either way...on and off rain chances are a good bet
across much of the state on Sunday...so if you have outdoor plans,
Saturday is your better bet for a warm and dry day outside! Highs
on Sunday will range from the 60s in the northwest to the lower
70s in the southeast. Cooler and drier air will move across
Arkansas behind this upper level system Sunday night into Monday.

Cavanaugh

&&

.LONG TERM...Monday Through Friday

By Sunday night, rain will start to taper off some, as the cold
front moves eastward. However, by this time, the trough digging down
into the midsouth region is expected to form a cutoff low. There`s
some spread in model solutions beyond this point, but most are
clustering in on the low moving out of the region Monday afternoon
or night. At that point, rain chances will come to an end.

Colder air will move into the region on Tuesday. This will be even
more so on Tuesday night, as a cutoff low forms over the Great Lakes
Region and the upper flow becomes more meridional. Lows on Wednesday
morning will fall into the 40s, with highs mainly in the 60s during
the afternoon. A few places in the northwest may even stay in the
50s.

The aforementioned cutoff low will move eastward on Wednesday and
the upper flow will become more zonal. Surface high pressure passing
through will bring more of a southerly component to the winds, which
will allow temperatures to moderate.

Any moderation, though, will be short-lived, as another powerful
upper trough digs down into the Southern Plains at the end of the
week. This will push another cold front into the region, with
showers and thunderstorms expected. Behind that system (in other
words, just beyond the end of the period), there could be a more
significant push of cold air. But, that`s a discussion we will have
to have at another time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     62  75  65  69 /  10  20  90  90
Camden AR         66  78  69  73 /  20  30  80  80
Harrison AR       60  74  57  60 /  20  20 100  60
Hot Springs AR    64  76  66  66 /  20  30  90  70
Little Rock   AR  64  78  68  72 /  10  20  80  80
Monticello AR     65  80  69  74 /  10  30  50  90
Mount Ida AR      63  75  64  63 /  20  30  90  70
Mountain Home AR  64  75  61  63 /  20  20 100  70
Newport AR        61  77  66  73 /  10  20  80  90
Pine Bluff AR     64  79  68  74 /  10  20  70  80
Russellville AR   63  76  65  65 /  20  20  90  70
Searcy AR         62  77  66  72 /  10  20  80  80
Stuttgart AR      63  78  68  75 /  10  20  70  90
&&

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

$$

Short Term...CAVANAUGH / Long Term...57


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