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 251729

1129 AM CST Tue Nov 25 2014

.SHORT TERM: (Today through Wednesday Night)
Issued at 325 AM CST Tue Nov 25 2014

West-northwest flow will continue through most of the day today
as a weak surface ridge tries to move into the Mississippi Valley.
Short range guidance is indicating that the clouds currently over
northeast Missouri and west central Illinois should clear out
during the morning. Expect temperatures to rise into 35-40 degree
range across most of the area under a partly to mostly sunny sky

Meanwhile, shortwave upstream over Alberta will dive down into the
longwave trof over the central CONUS.  The surface clipper is now
forecast to dive southeast through the Missouri Valley tonight and
early Wednesday morning.  Guidance seems to be in pretty good
agreement that the surface low will be near Kirksville at around 18Z
Wednesday.  Low will continue off to the southeast into Kentucky
Wednesday night.  Mid-level shortwave energy combined with weak to
moderate frontogenetical forcing and even some upper level
divergence on the left exit region of an upper level jet streak will
combine to produce a band of precip which will affect areas
primarily along and east of the low track.  This will encompass most
if not all of our CWFA on Wednesday.  BUFKIT soundings from the NAM
and GFS do support mostly snow during the morning, with a potential
for mix of snow and/or rain in the afternoon.  Expect surface
temperatures to be near or just above freezing at the initial
outset with slowly rising temperatures through the day.  Current
thinking is that accumulations will be an inch or less, but this
could change quite a bit if the low shifts its track either to the
west or to the east.  Some lingering sprinkles or light snow will
likely continue over eastern areas during the evening, drying out
overnight with lows dipping back into the 20s.


.LONG TERM:  (Thursday through Monday)
Issued at 350 AM CST Tue Nov 25 2014

Cool on Thanksgiving Day behind Wednesday`s system as a 1035mb high
builds into the Mississippi Valley with highs struggling into the
low to mid 30s across most of the area.  However, the longwave trof
over the eastern CONUS will begin to translate eastward later
Thursday and Thursday night.  This pattern shift will set up a
warming trend for Friday and Saturday.  Southwest flow will prevail
both days which will provide us with increasing low level moisture
as well as warming temperatures.  Temperatures will rise into the
40s and 50s Friday and mid 50s to low 60s Saturday.  Both GFS and
ECMWF show some transient areas of light QPF on Saturday, but
believe this is the typical reaction to strong low level moisture
advection.  In most of these cases there is little if any actual
precipitation.  Another clipper moves across the Upper Midwest which
drags a cold front into northern Missouri Saturday night into
Sunday.  This front becomes quasi-stationary over our area which
will make temperature forecasting for Sunday and Monday quite
difficult.  Medium range guidance is in good agreement at this time
with the front dipping south Sunday night and Monday as a strong
high pressure system dips into the Northern Plains from Canada and
then shifts eastward across the Upper Midwest.  Both GFS and ECMWF
print out precip as the front moves south...looks like most likely
from over-running warm advection at 850mb.  Think chance/slight
chance PoPs in the MOS blend look good at this time with slowly
falling temperatures for Sunday through Monday.



.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1115 AM CST Tue Nov 25 2014

VFR and dry conditions expected thru 12z Tues. Clouds will
gradually move into the region, thicken and lower thru this
period. Winds will gradually back to swly this afternoon and
become sely late tonight. Precip is expected to begin as all SN
at all terminals Tues mid to late morning depending on site.
Latest guidance suggests COU will change to RA around 18z, while
UIN will remain SN thru the afternoon. Much more uncertainty
exists for SUS/CPS with the sfc fnt in the region, but may change
to a RASN mix in the afternoon.

Specifics for KSTL: VFR and dry thru 15z Tues. Winds will be aob 8
kts and gradually back and become light and vrb tonight. Winds
will pick up out of the SE Tues morning. Precip is expected to
start as SN and possibly mix with RA during the late afternoon.
However, have low confidence in precip type during the afternoon.





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