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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KLZK 191730
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
1230 PM CDT Mon Apr 19 2021

.UPDATE...

Updated to include the 18Z aviation discussion.

&&

.AVIATION...

VFR conditions are forecast for all terminals during the period.
Mostly clear conditions are expected Monday afternoon, with light
westerly winds. Winds will become more southwesterly overnight.
Scattered cloud cover will expand over the southern parts of the
state overnight.

Cloud cover will increase from the NW Tuesday morning as a cold
front enters the state, bringing rain showers that will expand
across the northern half of the state by Tuesday afternoon.

&&

.PREV DISCUSSION...(ISSUED 633 AM CDT Mon Apr 19 2021)
UPDATE...

Updated to include the 12Z aviation discussion.

AVIATION...

Aside from patchy BR/FG this morning, VFR conditions will prevail
at all terminals this period. Winds will remain W/SW at or below
10 kts, becoming light/VRB overnight. High clouds may move over
southern terminals this afternoon with cloud cover increasing for
northern terminals near the end of the period.

PREV DISCUSSION...(ISSUED 418 AM CDT Mon Apr 19 2021)
SHORT TERM...Today Through Tuesday Night

Morning mesoanalysis depicts an elongated area of low-amplitude
mid/upper troughing stretching from near New England southwestward
to the Baja peninsula, punctuated by modest shortwave impulses.
The embedded shortwave responsible for yesterday`s rain and
thunder continues pushing east across the TN Valley with a surface
ridge expanding across the south- central CONUS. Do expect
tranquil weather today and tonight with temps running near to
slightly below average, yielding highs in the upper 60s to low 70s
and lows in the 40s tonight.

Meanwhile, water vapor imagery shows the next mid/upper trough
queuing up across the northern Rockies. While guidance has
trended a touch slower with this feature, do still expect it will
cross the central Rockies overnight and move across the Plains
states through the day Tuesday before pivoting northeast over MO
by Tuesday evening. Attendant to this upper feature is a strong
Canadian cold front, poised to sweep across the area Tuesday into
Tuesday night.

Ahead of the front, temps will climb to near average over roughly
the southeastern half of the state. Over the northwest, increasing
cloud cover ahead of and strong cold air advection in the wake of
the front will limit high temps to the 40s and 50s. Moisture
remains modest given the lack of substantial return flow from the
Gulf, although PWAT values on the order of 0.75 to 0.8 inches will
be enough to squeeze out rain showers along and ahead of the
front, primarily over the northern half of AR where moisture and
dynamic forcing are most in phase. That said, there could be
enough moisture farther south to generate isolated to scattered
showers, but confidence in more widespread coverage remains very
low. Winds will pick up markedly as the front approaches with
breezy westerly winds becoming north to northwesterly behind the
boundary. Wind headlines are not anticipated, although gusts could
approach 30 mph Tuesday afternoon and evening.

Temps will quickly fall in the wake of the front, both at the
surface and in the lower troposphere. Based on forecast soundings,
ensemble guidance, and calibrated statistical guidance, there is a
small window for mixed wintry precip over northern AR Tuesday
night assuming moisture isn`t entirely scoured out by then.
Should any wintry precip materialize, no accumulation or impacts
are expected and precip will end before dawn on Wednesday.

Of more consequence will be temperatures very late in the period
as the post-frontal Canadian air mass begins to settle over the
area. Initialized guidance remains on the warm side, likely a
consequence of climatological influence, so skewed temps Tuesday
night closely to the 25th percentile which yields near to sub-
freezing temps over roughly the northwestern half of AR. Readings
in the mid/upper 20s are likely over northwestern AR. Based on
this trend, did expand the Freeze Watch to include Polk, Randolph,
and Lawrence Counties with no changes to the remainder of the
watch. Sensitive vegetation is certainly at risk given the
magnitude of cold air expected and several record lows may be
challenged if not broken.

Strong surface ridging immediately behind the front suggests
winds will drop off fairly quickly Tuesday night. Clearing skies
and light winds in the presence of the anticipated cold will
readily produce frost over a large area. Did include patchy frost
as far south as a Camden to Pine Bluff to Stuttgart line with
widespread frost expected farther north and west. While min temps
over the southeastern half of the area will likely end up near to
above freezing, sensitive vegetation will still be at risk from
frost, so please prepare accordingly.

LONG TERM...Wednesday Through Sunday

A large area of Canadian high pressure will follow a cold front,
and will build into Arkansas by Wednesday morning. Low temperatures
will be in the upper 20s to upper 30s, with a freeze likely
in much of the Ozark and Ouachita Mountains. Frost will be
widespread as well.

Temperatures will start slowly modifying on Thursday as the high
exits to the east and return flow kicks in. Even so, readings will
remain below average. A large storm system will approach from the
southern Plains on Friday, with rain becoming widespread. There may
be rumbles of thunder as well. Amounts from a half inch to an inch
are expected, with the heaviest totals in southern sections of the
state.

Precipitation will begin tapering off Saturday as another cold
front arrives from the north with drier air. Temperatures will get
closer to seasonal as the period ends, but may still fall a little
short.

There should be additional warming beyond the period as ridging
occurs over the middle of the country ahead of a large storm
system/trough out west.

&&

.LZK Watches/Warnings/Advisories...
Freeze Watch from late Tuesday night through Wednesday morning
FOR Baxter-Boone-Cleburne-Conway-Fulton-Independence-Izard-
Johnson-Lawrence-Logan-Marion-Montgomery-Newton-Polk-Pope-
Randolph-Scott-Searcy-Sharp-Stone-Van Buren-Yell.

&&

$$


Aviation...SHELTON