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000
FXUS63 KLSX 160313
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1013 PM CDT Sat Mar 15 2014

.UPDATE:
Issued at 958 PM CDT Sat Mar 15 2014

Mdl data for the 00z cycle is just beginning to role in.
Therefore, only minor changes have been made to the going forecast
as only the NAM has arrived so far. Main changes made were to
account for current RADAR trends. Day shift discounted the NAM,
which at the time seemed reasonable. However, am beginning to
wonder if the GFS/ECMWF aerial coverage of precip is too much. If
trends continue, adjustments may be needed. Aside from timing of
precip and poss amounts, the general trends are expected to
continue. Frontogenetical band over IA shud continue to push swd
tonight. As it does, it shud also begin to diminish after sunrise.
Precip associated with the low spread ewd across the srn half of
the CWA. However, am becoming concerned that as the main s/w moves
ewd during the day Sun, that the moisture transport will shift to
the e out of the region. Low level forcing also quickly shifts
ewd. This may cause a swd shift in the precip maximum and may
reduce precip amounts overall. Precip may come to an end earlier
as well, but currently not by an appreciable amount of time.

Tilly

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 405 PM CDT Sat Mar 15 2014

Rain will spread northeastward as a southern stream shortwave over
the TX Panhandle moves northeastward towards southwest MO and a
northern stream wave now over WY and western CO drops
southeastward through the Plains on the heels of the southern
stream shortwave. Upper level divergence will be increasing
tonight, particularly across the southern half of our forecast
area. At the same time a cold front will be dropping southward
through our area. The models were depicting a frontogenetical band
of snow late tonight across northeast MO and west central IL
behind the surface front. Accumulations of up to one inch are
expected across northeast MO. Further south rain is expected,
possibly changing to sleet towards morning across central MO as
the surface layer cools to the freezing mark with an elevated warm
layer above freezing.

GKS

.LONG TERM:  (Sunday through Next Saturday)
Issued at 405 PM CDT Sat Mar 15 2014

Deformation type precipitation is expected on Sunday as a
surface/850 mb low moves across AR and into TN and northern portions
of MS AL.  Most of the precipitation will be south of Interstate
70. The precipitation type across southeast MO and southwest IL
will be initially rain, but will change to sleet and eventually to
snow as the elevated warm layer erodes. There may also be a brief
period of freezing rain in some areas before the rain changes over
to sleet. Will issue a winter weather advisory across southeast
MO and southwest IL into central MO where 2 to 4 inches of snow
along with sleet is expected. Temperatures will be nearly steady
on Sunday with cold air advection, low level clouds along with
precipitation. Surface winds will be very strong and gusty due to
the tight surface pressure gradient between the strong surface
ridge over the northern Plains and the surface low well south of
our area. The precipitation should shift southeast of our area by
Sunday evening as the upper level trough shifts east of the region
and the surface ridge builds southeastward through our area.
Below normal temperatures are expected Sunday night with a
clearing sky and a diminishing wind. A warming trend will begin
Monday afternoon as southerly flow returns as the surface ridge
shifts east of our area. An upper level trough and associated cold
front will mvoe eastward through the region Tuesday night. It
appears that most of the precipitation will remain north of our
forecast area along and north of the track of the surface low.

GKS

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 649 PM CDT Sat Mar 15 2014

Latest surface analysis shows quasi-stationary frontal boundary
extending from southern Indiana through northeast Kansas then
southwest to area of low pressure over south-central Kansas.
Quasi-statinnary frontal boundary expected to move southward over
night acrpss easterm Missouri and southwest Illinois. A weather
system over Texas is forecast to move east and bring light rain
over the area after midnight and then change over to a mixture of
ice pellets and snow after 1000 UTC over STL area and 0900 UTC
over central Missouri. Light snow will continue during the morning
hours over STLarea. surface winds will be gusty up to 30 kts from
the northeast early Sunday morning.

Specifics for KSTL: Quasi-stationary front expected to move south
across STL between 0300 and 0400 UTC. Surface winds will becoming
northeast with gusts 25 to 30 kts after 0900 UTC. Rainshowers
forecast to begin after 0600 UTC with rain changing to sleet and
snow after 0900 UTC. Surface winds will remain from the north-
northeast with gusts of 20 to 30 kts after 0900 UTC. Sleet and
snow will change over to all snow around 1400-1500 UTC. Light snow
will end during the mid to late afternoon hours.

Przybylinski

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...WINTER WEATHER ADVISORY from 4 AM to 7 PM CDT Sunday FOR
     Crawford MO-Franklin MO-Gasconade MO-Iron MO-Jefferson MO-
     Madison MO-Osage MO-Reynolds MO-St. Francois MO-Ste.
     Genevieve MO-Washington MO.

IL...WINTER WEATHER ADVISORY from 4 AM to 7 PM CDT Sunday FOR Clinton
     IL-Marion IL-Monroe IL-Randolph IL-St. Clair IL-Washington
     IL.

&&

$$

WFO LSX