132 
FXUS64 KLZK 242141
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
341 PM CST Sun Dec 24 2017

.Discussion...
GOES 16/East Water Vapor imagery current shows 
longwave troughing across the central CONUS with a moderate 
upstream ridge. As the mid- south shortwave trough rotates around 
the longwave trough, upper flow is expected to gradually "flatten"
out over the next couple days -- leading to quasi-zonal or WNW 
flow. A few weak perturbations in the flow will move across, with 
only minor response to the surface sensible weather. 

In the near term... Subsidence in the wake of a trough has finally 
spread across western Arkansas, clearing skies across much of the 
state. Areas of fog/drizzle or even flurries are limited to extreme 
eastern Arkansas (and NE Arkansas for the flurries). Any precip and 
most clouds will soon dissipate as dry air / subsidence prevails.

.SHORT TERM...Today Through Tuesday
For the short term period, very good agreement exists between all 
the primary global and [relevant] regions models. With cold air in 
place, temperatures will drop below freezing statewide. Surface high 
currently located over the south/central plains will gradually shift 
eastwards over Arkansas. The pressure gradient will initially be 
strong enough to keep winds high and the near-surface layer mixed 
such that maximized cooling isn't realized. Eventually, across the 
western half of the CWA, winds will go to near calm. By then 
however, onset of high clouds will likely radiate enough heat back 
to prevent maximized diurnal cooling. All that said, temperatures 
will range from the mid teens to the upper 20s tonight -- the 
perfect temperatures for landing sleighs on roofs. Highs Christmas 
day will range from the mid 30s in northern Arkansas to mid 40s near 
Louisiana. 

A weak perturbation in the upper flow will move across Arkansas 
Monday night into Tuesday morning. Only a weak surface response in 
the form of variable winds is expected before easterly to 
southeasterly winds resume as strong surface high builds in the 
midwest CONUS.

Tuesday will be another cold day with the cold airmass still in 
place. Skies will begin mostly clear at first before mid-level 
isentropic lift begins in response to strengthening pressure 
gradient from high plains / intermountain west cyclogenesis brings 
in some mid level clouds from the south. At this point in time, it 
doesn't appear lift and moisture will be sufficient for much 
precipitation until later in the forecast. See long term.

&&

.LONG TERM...Tuesday Night Through Saturday
The period begins with continued large scale longwave troughing 
across the central CONUS with reinforcing shots of cold air sweeping 
southward from the Arctic. Within this trough structure, embedded 
shortwave energy will be the primary focus for any precipitation 
episodes, although the details are unfortunately yet-to-be-
reasonably-resolved by model guidance or human interpretation of 
said guidance. The sure bet going forward is the pattern will be 
seasonably cold and periodically fitful with winter precipitation 
possible around mid week and potentially again over New Years 
weekend. 

The 12Z suite of model guidance has largely failed to converge on a 
common solution, with large run-to-run inconsistencies noted with 
the past several GFS runs. The operational ECMWF retains a bone dry 
solution for the mid week time frame, opposite the wetter 
operational GFS solution. Ensemble guidance shows little consensus 
with large discrepancies among individual members. One potential 
trend within the guidance is for a weaker impulse overall, which 
would largely negate a more impactful system. Model QPF fields that 
do show precipitation (e.g., the GFS) advertise low QPF, generally a 
couple hundredths of an inch liquid equivalent. Decided to keep only 
slight chance PoPs area wide with a small area of low-end chance 
PoPs in far southeastern counties until the system is better 
resolved in the guidance. Precipitation will creep in from the south 
late Wednesday night into Thursday morning.

As for precipitation type: model forecast soundings generally 
support an overall mode of snow across roughly the northern third of 
the state; a mix of sleet, snow, freezing rain, and rain across the 
central third of the state; and a mix transitioning to rain across 
roughly the southern third of the state. To stress the point -- this 
is a low confidence forecast and impacts, as of now, are expected to 
be minimal. Did include a 0.1 inch snow accumulation contour across 
northern zones where temperatures will remain near or below freezing 
throughout the day Thursday. Precipitation will end northwest to 
southeast late Thursday into Friday. 

After a brief lull late Friday into early Saturday, another and 
potentially more powerful shortwave trough will approach the area
for the end of the period and beyond. Large model discrepancies 
preclude more specific PoP fields and timing, but did include a 
broad brushed area of slight chance PoPs with wintry precipitation
possible again to round out the long term.

Cooper

&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     40  22  39  25 /  20   0   0  10 
Camden AR         49  25  45  28 /  10   0   0  10 
Harrison AR       33  19  37  23 /  20   0   0  10 
Hot Springs AR    45  25  43  27 /  10   0   0   0 
Little Rock   AR  46  25  41  28 /  20   0   0   0 
Monticello AR     47  25  43  30 /  10   0   0   0 
Mount Ida AR      45  23  43  26 /  10   0   0   0 
Mountain Home AR  35  19  38  21 /  20   0   0  10 
Newport AR        40  22  39  27 /  20   0   0  10 
Pine Bluff AR     47  25  42  29 /  20   0   0   0 
Russellville AR   43  22  41  27 /  20   0   0   0 
Searcy AR         45  24  40  26 /  20   0   0   0 
Stuttgart AR      46  25  40  29 /  20   0   0   0 
&&

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

$$

Short Term...BROWN / Long Term...COOPER