Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 032318 AAA
AFDLZK

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
518 PM CST Sat Dec 3 2016

.DISCUSSION...

Updated to include the 00Z aviation discussion below...

&&

.AVIATION...

Widespread rain continues across the area early this
evening...which will continue over the next several hrs before
coverage becomes a bit more scattered. As this happens...do think
the VIS will decrease as some fog develops. By midday
Sun...rainfall coverage should become isolated if not
absent...with some improving conditions expected.

&&

.PREV DISCUSSION...(ISSUED 251 PM CST Sat Dec 3 2016)

Short Term...Tonight through Monday...

The principal weather concern this afternoon is still the upper
level low located over western North America. Water vapor imagery
reveals the low centered along the Sonoran coast on the Gulf of
California, drifting slowly eastward. Analysis of a diverse set of
model data shows fairly good consistency in moving this low
eastward over the next 48 hours into the Ern OK/Nern Tx region,
with the trof becoming negatively tilted.

The low will continue to kick out shortwaves across the area until
it approaches late in the period. Best rain chances will be tonight
through early tomorrow, and again on Monday as the upper level low
approaches.

Midlevel lapse rates will become quite a bit steeper on Monday as
the low approaches the area, and there will be an impressive amount
of upper level difluence to the northeast of the negatively tilted
trof and upper low. Although surface temperatures will remain on the
low side and there will not be much instability in the lower layers,
I have opted to include isolated thunderstorms in the forecast
during the day on Monday due to the aforementioned reasons -
principally for the southeast half of the forecast area.

At the surface the area will remain under the control of high
pressure, and a northerly wind component will continue throughout
the period.

QPF values are always a bit tricky, but under the current scenario
the heaviest rainfall should remain primarily in the southeast, with
average basin values in the one inch range this afternoon and
tonight, with locally higher amounts approaching two inches. Outside
of the southeast rainfall totals will be quite a bit less.

As for aviation concerns...flying weather is going to be rather
lousy for the remainder of the afternoon and tonight for most sites.
LIFR conditions are already present at a number of sites across the
south, with IFR conditions generally across the rest of the south.
By midnight tonight I am anticipating LIFR conditions at all of our
TAF sites.

LONG TERM...Monday Night Through Saturday...

Widespread rain will be ongoing Monday night as a strong upper
low moves directly over Arkansas after lifting northeast out of
south Texas. The upper low will is also associated with a cold
front that will move through the area between midnight and sunrise
Tuesday. The rain should rapidly end from west to east Tuesday
morning and be completely out of the CWA by noon. Being primarily
north of the warm front, thunder appears unlikely, but if it does
occur it will be across southern portions of the CWA. Strong
storms are NOT expected.

Mostly dry Tuesday night in advance of a reinforcing arctic front
to move though the state Wed...most likely during the afternoon in
Little Rock. Virtually all models are in agreement in bringing some
post frontal precip with the front, so have included pops in the
forecast Wed and Wed night. It`s possible that precip could linger
just long enough Wed night that a brief bout of light snow or
rain/snow mix may occur across the northwestern portions of the
state, and most likely occurring in the higher elevations. At this
point little or no accumulations are expected. However, this bears
watching as temps and timing of this system are difficult to predict
this far out. Regardless, any snow will not last long. It is also
worst noting that the GFS is faster with the frontal passage with
less precip than the ECMWF. The ECMWF actually keeps pops around on
Thu, but this model appears to be the outlier.

Much colder temps anticipated Wed night through the weekend, with
another arctic cold front possible Sunday. Rain may accompany that
front as well. Thu night could be the coldest temps we have
experienced since the winter of 2014-15, since our coldest low at
Little Rock last winter was 22F. Wind chills Thu should stay mainly
in the 20s.

&&

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

$$


Aviation...62


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