Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KLSX 202335

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
635 PM CDT Tue Mar 20 2018

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 346 PM CDT Tue Mar 20 2018

Surface high pressure over the Great Plains will build slowly east
through Wednesday.  Water vapor imagery is showing a shortwave over
South Dakota and Nebraska that will drop southeast through the
Missouri Valley across western Missouri tonight. Short range
guidance is developing some light precip over west central and
central Missouri this evening as the wave ripples by.  Low levels
look relatively dry so I`m not sure how much precip will actually
reach the ground.  Regardless, thermal profiles suggest that the
most likely precip type will be liquid if anything does reach the
ground.  Clouds overnight will likely keep temperatures from
bottoming out too hard, but lows in the upper 20s to low 30s look
likely.  Should see a clearing sky on Wednesday as high pressure
continues building into the Mississippi Valley from the west.  March
sunshine is expected to help temperatures rebound into the upper 40s
and low 50s.


.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 346 PM CDT Tue Mar 20 2018

Low level flow turns back to the southwest on Thursday as the
surface high moves east of the Mississippi Valley.  Models have been
consistently printing out precip Thursday and Thursday night as the
nose of a 20-30kt low level jet pushes into the 850mb baroclinic
zone resulting in weak to moderate moisture convergence and
isentropic lift.  There`s still some question though about how much
moisture will be available to generate precip as the retreating
ridge axis extends all the way south into the central Gulf of
Mexico.  Have therefore limited PoPs to the chance range rather than
going higher in spite of the model consistency and good agreement.

Medium range guidance is trying to come into better agreement for
Friday through Sunday with the next storm system.  The low is
forecast to develop over eastern Colorado and western Kansas late
Friday and move into Missouri Saturday.  The low moves east-
southeast into the Tennessee Valley by Saturday night and the
southern edge of a large Canadian high pushes in from the northeast
behind the low.  This looks like another good chance for rain across
much of Missouri and Illinois...with strong moisture convergence
wrapping around the cold sector of the low.  Sunday looks dry at
this time between a strong upper level ridge moving overhead and the
surface high pushing cool dry air in from the east and northeast.
The longwave pattern continues to progress east with a deep trof
developing over the Western U.S. and the upper ridge moving over the
Eastern Seaboard on Monday. Resulting southwest flow over the
Central U.S. will provide deep moisture return into the Mississippi
Valley and an increasing chance for rain early next week.



.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 614 PM CDT Tue Mar 20 2018

Nwly to nly flow expected thru the TAF period. Believe cigs will
remain VFR, however, some MVFR cigs may develop further west and
impact COU. There is also a chance of rain, or perhaps light snow,
impacting COU tonight.

SPECIFICS FOR KSTL: VFR conditions thru the period expected. Winds
will remain nwly to nly and increase Wed morning, then diminish
again after sunset.



Saint Louis     33  49  33  54 /   5   0   0  40
Quincy          29  47  30  50 /  10   0   0  50
Columbia        32  51  33  61 /  10   0   0  10
Jefferson City  32  52  31  62 /  10   0   0   5
Salem           32  47  29  52 /  10   0   0  30
Farmington      31  50  30  58 /  10   0   0  10




WFO LSX is the U.S. government's official web portal to all federal, state and local government web resources and services.