Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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899
FXUS63 KEAX 011150
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
550 AM CST Thu Dec 1 2016

.Discussion...
Issued at 247 AM CST THU DEC 1 2016

Quiet short-term forecast as the upper low over the Great Lakes
region continues to slide off to the northeast. Any lift generated by
the upper low and contributing to flurries yesterday has also shifted
far enough out of the region that even where stratus lingers today in
northeast MO, should not see any additional flakes fly. The back edge
of the upper trough will elongate and trail across the northern CONUS
as additional shortwave energy carves down its back, so even though
the main upper low will be moving off over the next few days, the
pathway for chilly Canadian air into the northern Plains will remain
mostly unchanged today and Friday, with perhaps just a degree or two
of potential warming each day. Lowered highs just a smidge in far
northeast MO today where stratus will be persistent, and also raised
highs a few degrees across far southern portions of the CWA where
there is potential for midlevel stratus to develop during the evening
and persist through the night, holding temperatures up.

Another trough currently edging into the Pac NW will deepen and slide
down the west coast over the next few days, eventually pushing over
the Rockies by Saturday and allowing colder 850 hPa temperatures to
drop down from the northwest, which will hold temperatures in the
lower 40s CWA-wide on Saturday afternoon; however, the colder 850
hPa temperatures will be short-lived as the upper trough continues to
slide east and southwesterly flow allows warmer conditions to build
into the region. A steady stream of energy and moisture is expected
to emanate from the southwestern U.S. into the Gulf Coast region, but
some moisture may overrun the system to the south and join up with a
northern-stream shortwave trough to bring light precipitation into
our forecast area Saturday night through early Sunday. Model
soundings continue to indicate a p-type of all rain, but have had to
include a rain/snow mix where surface temperatures are marginal.
Regardless, does not look like a situation where any wintry
precipitation accumulation is expected, and rain amounts will be
light due to the brevity of the system and limited moisture
availability.

Things get a little more interesting but a LOT more uncertain as
early as Monday when the deep upper low at the base of the trough
over the Baja Peninsula ejects out into the deep southern Plains.
Both the EC and GFS are in agreement that a surface low will develop
and swing up to the north northeast by midweek as the upper low melds
into the main upper flow and lifts northeast, but are still fairly
different in where the surface low develops, treks, and the character
of precipitation associated with the system. The GFS phases wrap-
around moisture on the northwest side of the low with a cold front
extending down from the next system to arrive, and paints a fairly
extended period of broad, light precipitation across the region
Tuesday night through Wednesday. The EC keeps the systems more
separate, but also brings light precipitation through with the cold
front from the next trough. The primary disagreement, which is key
this time of year, is the amount, extent, and arrival time of cold
air pushing down with the next trough. The GFS is very quick to bring
in frigid 850 hPa air; thus resulting in a p-type of mainly snow
throughout the CWA. The EC keep precipitation closer to the 850 hPa
temperature gradient, possibly bringing some snow into the region but
starting as rain and drying out when the cold air arrives, thus
accumulations would be pretty unlikely. Anecdotally, the EC solution
looks much more familiar and typical of early December than the GFS,
but will have to watch how these systems play out as uncertainty is
expectedly still very high.

&&

.Aviation...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 550 AM CST THU DEC 1 2016

Clear skies are expected at all TAF sites today, with the exception
of some possible stratus edging near KSTJ once again over the next
few hours. Currently, it appears stratus will stay just north of the
KSTJ terminal and bases should remain above 3 kft even if they do
briefly impinge on the airfield, and would then depart again to the
northeast by 15z. Winds will remain out of the west northwest at 7 to
10 kts throughout the day, then will become light and variable after
sunset.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...Laflin
Aviation...Laflin



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