Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | 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 221816

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1216 PM CST Sun Jan 22 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 351 AM CST Sun Jan 22 2017

Attention this prd will focus on storm system emerging from the
sthrn Plains. Closed low is expected to track from NE TX to wrn NC
while the assoc SFC low moves from NW AR to the sthrn Appalachians
from this mrng to Mon mrng. This set-up should spread decent precip
across the sthrn half of the FA but...the models have changed
significantly since 24 hrs ago. Now the precip shield is fcst to be
not nearly so robust. There should be two areas that have better
precip coverage. A SW-NE orientated frontogenetical band fcst to
dvlp over the next several hours across SE KS extending into NE MO.
This lift should persist most of the mrng with the band dssptng
around midday. Then another area of precip should lift N out of AR
thru the day as the lows pass just S of the CWA and then pivot
across the SErn FA drng the aftn. This solution means most of the
area largely misses out on the best precip chances. The threat of
rain diminishes from W-E drng the aftn with all but the far ern
zones expected to be dry by 00Z. PoP grids have correspondingly been
lowered. The highest PoPs this mrng are across cntrl and NE MO as
well as SE MO and then the focus on SE MO and sthrn IL for this
aftn. Winds should increase and become gusty thru the day as the
system passes E of the region. Gusty northerly winds should
continue overnight.

Despite the cloud cover and precip...temps should once again be well
above normal though not quite as warm as yesterday. Highs should
make it into the 50s with the exception of NE MO and W cntrl IL
where readings will hold in the mid/upper 40s...which is still 10-15
degrees above normal. Tonight will be cooler than the past two
nights but still above normal with lows in the 30s which is closer
to typical daytime highs for mid/late Jan.


.LONG TERM...  (Monday through Saturday)
Issued at 351 AM CST Sun Jan 22 2017

Breezy and cooler conditions will prevail on Monday morning, with
winds diminishing in the afternoon as the previous system continues
to advance well to the east and a weak surface high slides into the
area.  A deep long wave trof over the western U.S. will progress
eastward on Tuesday and Tuesday night with the lead upper low and
short wave trof moving out of the Rockies through the Plains and
into the mid/upper MS Valley by Wednesday morning. The accompanying
surface low and cold front will move across the CWA on Tuesday night,
but will be preceded by a strong WAA regime and moderating/above
average temperatures on Tuesday. Height falls aloft and weak large
scale ascent along and ahead of the advancing the cold front support
the potential for spotty/scattered showers across primarily northern
portions of the CWA.

A broad long wave trof will evolve during the later half of the week
over much of the CONUS with a series of disturbances impacting our
area within the increasingly cyclonic upper flow. The first of
these occurs in the Wednesday/Wednesday evening time frame, and
the ECMWF is a bit stronger and suggests enough forcing to
produce some light precipitation across the northern half of the
CWA. If this occurs it would largely be rain on Wednesday with a
potential for a rain/snow mix or some light snow on Wednesday

Temperatures will get back to near normal after Wednesday as the long
wave trof continues to evolve and the aforementioned disturbances
bring progressively colder air into the region.



.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1147 AM CST Sun Jan 22 2017

An area of mainly IFR ceilings along the I-44/I-55 corridor
should slowly dissipate this afternoon which should leave the area
with VFR ceilings into the evening. Expect the lower clouds over
northwest Missouri and Iowa to eventually move over our area
during the mid to late evening. Expect low-end MVFR and IFR
ceilings to then prevail through Monday morning. While these
general trends look sound...exact timing and ceiling heights are
low confidence.


Watching IFR ceilings at Lambert. Current satellite trend is to
clear out the low clouds, but confidence on timing is low right
now. Once the low clouds clear out, Lambert should stay VFR until
sometime during the late evening or early overnight hours. Again,
the timing on lowering ceilings is uncertain, but I leaned
pessimistically and brought ceilings down earlier than guidance
suggested. Once ceilings drop, expect low end MVFR or potentially
IFR to prevail through Monday morning with improving conditions in
the afternoon.





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