FXUS63 KLSX 182110

Area Forecast Discussion
National Weather Service Saint Louis MO
410 PM CDT Mon Mar 18 2019

.SHORT TERM... (Through Late Tuesday Afternoon)
Issued at 259 PM CDT Mon Mar 18 2019

The period is pleasantly quiet with few items to address. The main
focus will be on chances for precipitation ahead of the next system
late Tuesday.

Surface high pressure is position at the western edge of an upper
longwave trough with northwest flow aloft. Surface analysis shows
a spread in temperatures that range from the mid/upper 40s over
northeast Missouri and into interior portions of Illinois to the
mid/upper 50s over central and southeast Missouri.

Northwest flow continues to pump relatively drier air into the
area with just enough surface and mid-level moisture to result in
diurnal cu, mainly over far southeastern Missouri and central
Illinois. Given deeper mixing, what has developed generally
resides between 4k and 6k feet AGL. Satellite obs show some of
this eroding on the back side, which is likely due to lower RH
being pushing in from the northwest through the mid-levels.
Expect much of the evening to remain mostly sunny with cloud cover
giving way after diurnal heating is lost.

Tuesday is looking to remain dry for most locations with the main
region in question being over central Missouri. As the surface low
ejects east from the plains, it runs well ahead of the main upper
level shortwave that is passing southward through the central
plains. Ahead of the surface low, there is a relatively weak area
of mid-level lift associated with a warm front. However, moisture
is lacking through the surface and up to a certain point through
the mid layer, which has me less confident in any appreciable
precip. Therefore, much of the day is likely to remain dry with
maybe a widely scattered shower from Columbia to Quincy from late
morning into the early evening.

Otherwise, expect high clouds to stream in and thicken through the
morning as moisture continues to increase above 10k feet. Surface
flow turns out of the south/southwest, likely pushing temperatures
into the 50s, despite less sunshine that today.


.LONG TERM... (Tuesday Night through Next Monday)
Issued at 259 PM CDT Mon Mar 18 2019

Much of the long term is quiet, but bookended by precipitation
chances. Near normal temperatures will moderate late in the week
with above normal condition as we head into next weekend.

Rain chances will increase through late Tuesday afternoon into
Tuesday evening. Latest trends in guidance bring a surface low
from southwest to northeast through the heart of central
Missouri. This focuses better lift and core of deeper moisture
through central and northeast Missouri Tuesday evening and Tuesday
night. Further east, drier air remains in place through the low
and mid-levels, holding precipitation off until later in the

A cold front extending southwest of the surface low will begin to
push east through Tuesday night and into Wednesday morning. There
is enough moisture and convergence along the front that will
result in a linear pattern of scattered rain showers, most likely
through early Wednesday morning. Winds shifts out of the west
behind the front, but there isn't much cold air associate with the
surface wave. The main front moves through behind the upper level
shortwave late Wednesday with temperatures that will top out in
the 50s.

Much of the time is quiet beyond Wednesday as we settle back in
underneath northwest flow. A narrow, high amplitude upper ridge
begins to build northward through the central plains late this
week. As this move east, southerly flow develops and brings
milder, above normal temperatures to the region from Thursday into
Friday. It look like much of this could extend into the weekend as
surface high pressure builds over the Great Lakes and Midwest.
The next chance of rain may hold off until early next week. This
results from a broad and weak upper level wave that continue to
open up as it pushes into the Midwest. Surface dry layer may
impede much of the onset with plenty of time for changes to occur.
For now, it looks like low end chances for scattered rain showers
as we going into Monday with temperatures in the low 60s.



.AVIATION... (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1230 PM CDT Mon Mar 18 2019

VFR conditions are expected through the period with generally
light/variable winds today into tonight. Otherwise, diurnal cloud
development will result in few/scattered decks between 3k and 6k
feet through sunset this evening.

Our next system will approach from the west late Tuesday. While
precipitation is not expected until after the period in most
places, slight chances are possible at KCOU before the period
comes to a close.


Little concern through the period with VFR conditions and light
wind anticipated. Diurnal cu should remain widely scattered/few
this afternoon and fades with loss daytime heating.

An approaching system could introduce slight chances for rain
late Tuesday afternoon/evening. It is likely much of this holds
off until after nightfall given limited moisture.





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