Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252043
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
343 PM CDT WED MAY 25 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 248 PM CDT Wed May 25 2016

Convection across parts of southeast MO and southwest IL should
shift east-southeast of our forecast area by early this evening.
With shortwave energy shifting east-northeast of the region it
appears that most of the forecast area should be dry this evening.
Still a lot of uncertainty as to where convection will initiate
later tonight, but it appears that there may be convection
developing and moving into parts of northeast MO and west central
IL late tonight on the nose of a southwesterly low level jet. With
continued southerly surface winds and relatively high surface dew
points, lows tonight will be at least 10 degrees above normal for
late May and a little warmer than the previous night.

GKS

.LONG TERM...  (Thursday through Next Wednesday)
Issued at 248 PM CDT Wed May 25 2016

Low confidence forecast continues with regards to the location,
timing and coverage of convection expected with weak southwest
flow shortwaves continuing to move through the area coupled with
a warm, moist and unstable southerly low level flow. May be mainly
scattered diurnal convection during the afternoon and early
evening on Thursday with slightly warmer temperatures. Should see
an increase in cloud cover along with coverage of showers/storms
by Friday as an upper level trough/low over southwest US
approaches from the Plains. Will increase pops into the likely
catagory on Friday over the entire forecast area, along with
cooler high temperatures due to the increased cloud cover and
precipitation coverage/duration expected. This upper level trough
should shift northeast of our area by Saturday night with a lull
in the convective activity expected from Saturday night through
at least Sunday night. The warm and humid weather pattern should
continue for Memorial Day into the next work week with weak
southwest upper level flow and weak surface winds. Mainly
scattered diurnal convection is expected during the afternoons and
early evening hours. The ECMWF model does have an upper level
trough moving eastward through the northern Plains which sends a
cold front southeastward through our forecast area on Wednesday
which would be a focus for convection, but the GFS model does not
have these features, so for now will just have chance pops for
the end of the extended forecast period.

GKS

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 643 AM CDT Wed May 25 2016

Another difficult aviation forecast with lots of uncertainty in
coverage of showers and thunderstorms, timing, and location.
Scattered showers and thunderstorms have been developing from KCOU
eastward since around 10z and the threat for SHRA/TSRA either at
the terminal or in the vicinity will continue this morning. The
general thought is that most of the activity should shift to the
east of KCOU by mid-morning and east of the St. Louis area
terminals by midday. Another round of thunderstorms is anticipated
this afternoon originating over eastern MO/west-central IL and
hence the TEMPO group. A lull in precipitation is then expected
until later tonight when more showers and thunderstorms are
expected across northern MO into western IL impacting KUIN.

Specifics for KSTL:

Scattered showers and thunderstorms have been developing between
KCOU and KSTL since around 10z and the threat for SHRA/TSRA
either at the terminal or in the vicinity will continue until late
morning. Another round of thunderstorms is anticipated later this
afternoon originating over eastern MO, and hence the TEMPO group
from 21-00z. Most of the shower and thunderstorm activity tonight
is expected across northern MO into western IL, possibly drifting
southward to KSTL by early Thursday morning. Confidence is not
high enough to add any overnight mention at this time.


Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX


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