Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 182103

Area Forecast Discussion
National Weather Service Saint Louis MO
403 PM CDT Sun Mar 18 2018

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 402 PM CDT Sun Mar 18 2018

A strong shortwave over the Four Corners Region is moving east int o
the Great Plains and forcing cyclogenesis over eastern Colorado this
afternoon.  A broken band of showers and thunderstorms has already
formed over Oklahoma in the warm sector ahead of the low.  Short
range mesoscale models look to be handling the current weather
pretty have leaned heavily on them for timing and coverage
of precipitation tonight into Monday.  The band of showers over
Oklahoma should continue to spread northeast into Missouri this
evening, though current indications are that it will weaken and
potentially even dissipate as it moves into central and southeast
Missouri late this evening.  Focus then turns to precipitation on the
actual cold/warm front early Monday.  Guidance is showing strong low
level moisture convergence along the front wrapping back into the
triple-point and the occlusion as the low moves along the
Missouri/Arkansas border on Monday.  This will be the best chance
for rain as the occluded front moves through southeast Missouri late
Monday morning into the afternoon with lingering deformation zone
showers during the late afternoon into the evening.  Temperatures
will be very dependent on clouds and precip through Monday, but
expect it to be similar to today with highs perhaps a couple of
degrees warmer due to the warm advection ahead of the low.


.LONG TERM...  (Monday Night through Next Sunday)
Issued at 402 PM CDT Sun Mar 18 2018

Monday`s storm system will continue heading east at a good clip and
will be over North Carolina by early Tuesday morning.  Low level
north/northwest flow with with plenty of clouds in the wake of the
low.  Models show northwest flow over the Midwest with several
subtle shortwaves rippling south across our forecast area Tuesday
and Wednesday.  There should be sufficient moisture in the wake of
the low on Tuesday for these disturbances to produce a few sprinkles
or light showers...primarily across parts of southern Missouri.  The
persistent northwest flow will eventually dry up the low levels
Wednesday night...but another low is forecast to begin devleoping on
Thursday night into Friday which will turn the 850mb flow back to
the southwest.  Guidance spits out QPF due to 850mb moisture
convergence along and east of the Misssissippi River on Thursday
night into Friday.  Beyond that...medium range guidance diverges
quite sharply with the GFS being much faster than the ECMWF in
bringing the low through the Midwest.  Generally speaking though,
the pattern looks showery, tho timing is obviously low confidence.
Temperatures should be at or above seasonal normals.



.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1240 PM CDT Sun Mar 18 2018

Expect band of MVFR stratus to continue to persist across much of
eastern Missouri and west central and southwest Illinois through
this afternoon and into tonight. There is erosion of the cloud
mass from the southwest and the northeast, it is very slow and
think the majority of the area will stay broken to overcast with
MVFR ceilings between 1000-2000 feet. Any locations that do
scatter out will likely fill back in after sunset. Low pressure is
expected to move from Colorado across the Plains and along the
Missouri/Arkansas border tonight through Monday. Showers and a few
thunderstorms are likely starting tonight and continuing into
Monday as the system moves through. The highest chance for rain
will be mainly across central, east central, and southeast
Missouri as well as southwest and south central Illinois. While
low MVFR ceilings are expected to prevail through Monday, heavier
rain showers and thunderstorms could bring ceilings/visibilities
down to IFR at times.


Expect MVFR stratus with bases between 1200-1800 feet to prevail
at Lambert through most of the forecast period. Isolated showers
Current thinking is that rain showers are possible after 09-12Z,
and more persistent rain will overspread the STL metro area during
the late morning or early afternoon. IFR conditions are possible
with this heavier rain, but there seems to be little consensus in
model guidance on this question.



Saint Louis     41  52  34  48 /  30  90  80  10
Quincy          39  53  31  44 /   5  40  30   5
Columbia        41  50  33  48 /  40  80  60  10
Jefferson City  42  50  35  49 /  50  90  60  10
Salem           41  54  33  47 /  20  90  80  10
Farmington      42  52  35  49 /  70  90  70  20




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