862 
FXUS63 KLSX 261212
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
712 AM CDT Mon May 26 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Mon May 26 2014

Expecting summertime weather for Memorial Day.  Upper ridge axis is 
east of the area over the Ohio Valley with Southwest flow through 
the depth of the troposphere.  Warm and humid air will continue to 
persist over the mid Mississippi Valley today.  Convection over 
western Missouri looks to have produced an outflow boundary which is 
propagating northeast this morning, and this boundary may be a focus 
for convection once daytime heating is added to the mix.  There is 
also a subtle shortwave moving northeast into Missouri from eastern 
Kansas which could enhance convection late this morning and this 
afternoon over central and northeast Missouri.  Further east, think 
outflow boundaries combined with diurnal heating should provide 
triggers for afternoon convection.  Have bumped pops up to likely in 
central and northeast Missouri by 18Z, with mid-high chance further 
east.  Used a combination of 850mb mix-down temperatures and MOS 
guidance for highs today, which yields max temps in the mid to upper 
80s.

Carney

.LONG TERM:  (Tonight through Sunday)
Issued at 330 AM CDT Mon May 26 2014

A longwave upper ridge over the central CONUS will remain the 
dominant feature into the early part of next weekend, ensuring the 
temperature regime will be one that is above average thru the 
period. 

A cutoff storm system over northern NM is expected to continue to 
drift eastward into the southern Plains by Tuesday, and towards the 
MS Delta region by Thursday.  During this time, it is expected to 
miss giving our region a direct hit, but will still hurl several 
upper level disturbances into our region thru Tuesday from the 
southerly flow ahead of it.  Additional disturbances will work their 
way down Wednesday and Thursday from the north, and will be coupled 
with, for a time, a backdoor front.  This front will then probably 
linger into Friday and perhaps Saturday.

All of this will be acting on what should be a remarkably similar 
atmospheric column from day-to-day.  One that is unusually moist for 
this time of year, with little-no CINH, and enough instability for 
thunder; but shear will be much too weak with freezing levels 
sufficiently hi to largely preclude any widespread severe wx.  PoPs 
should peak during the afternoon with peak heating and fade by late 
night and early morning, repeating the cycle each day and enhancing 
when it can latch on to an upper level disturbance as detailed in 
the preceding paragraph.  Kept PoPs in the 20-50% range each day, 
trending towards climo PoPs of 25% towards late week.

TES

&&

.AVIATION:  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 645 AM CDT Mon May 26 2014

VFR flight conditions and southwest flow will prevail through late
morning across the area. Early morning fog in sheltered areas should
dissipate within the next hour. Expecting scattered to numerous
showers and thunderstorms to develop by early afternoon. Greatest
coverage is expected to be across central and northeast Missouri
as well as west central Illinois. While confidence is high that
there will be storms, am less confident on timing and over all
coverage so have only continued VCTS rather than upgrading to
TEMPO in terminal forecasts. VFR conditions should prevail outside
of storms this afternoon. Guidance is in good agreement that the
storms will not last long past 00Z. Any areas that receive rain
today will also likely see some light fog late tonight as well.

Specifics for KSTL:

VFR flight conditions and southwest flow will prevail through
early afternoon at Lambert. Expecting scattered showers and
thunderstorms to develop by early afternoon in the vicinity of the
terminal. While confidence is high that there will be storms
around the STL Metro area, am less confident on timing and over all
coverage so have only continued VCTS rather than upgrading to
TEMPO. VFR conditions should prevail outside of storms this
afternoon. Guidance is in good agreement that the storms will not
last long past 00Z. 

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX