141 
FXUS63 KLSX 262035
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
335 PM CDT Thu Jun 26 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 333 PM CDT Thu Jun 26 2014

Expect spotty afternoon convection to dissipate early this evening 
with loss of heating, but anticipate another uptick in PoPs during 
the predawn hours (primarily west of the Mississippi River) as 
shortwave/MCV, or possibly outflow from upstream convection, 
approaches and moves into western sections of our CWA.   For the 
time being have kept PoPs in the slight chance category for the 
overnight hours which may be too low, but there is certainly a lack 
of support from any of the hi-res solutions to go higher at this 
time.   Lows should be be similar to those of last night, generally 
in the 65-70 range.

Truett

.LONG TERM:  (Friday through Next Thursday)
Issued at 333 PM CDT Thu Jun 26 2014

Could not rule out showers and thunderstorms in the morning ahead of 
the MCV currently moving slowly eastward through KS, although the 
better coverage may still continue to be during the afternoon and 
early evening hours when the atmosphere is the most unstable due to 
surface heating. The models do not have much qpf for Friday night, 
but then ramp up convection by Saturday afternoon which should 
continue Saturday night as a negatively tilted upper level trough 
moves through the northern Plains.  Do not trust the GFS qpf output 
during this time period due to its convective feedback issues.  Will 
go close to the warmer high temperatures of the GFS MOS for Friday 
and Saturday over the cooler NAM MOS.  The NAM MOS appears too cool 
at least partially due to its greater low level cloud cover forecast 
during the afternoon hours which appears overdone.  The best 
potential for convection on Sunday should be across southeast MO and 
southwest IL where there will be the best low-mid level moisture and 
instability just ahead of the last shortwave trough.  The GFS model 
keeps convection north of our forecast area Sunday night and Monday 
as an upper level trough moves eastward through the northern Plains, 
then has a little qpf for us Monday night into Tuesday as a 
weakening cold front drops southeastward through our area.  The 
ECMWF model drops a possible MCS southeastward into our forecast 
area already by Monday morning, then also has convection along the 
cold front Monday night and Tuesday.  There may be lingering 
convection across southeast MO and southwest IL Tuesday night near 
the weak frontal boundary.  The GFS model brings slightly cooler and 
drier air into at least northeast MO and west central IL Wednesday 
and Wednesday night as a surface ridge builds southeastward into our 
area behind the cold front.  The ECMWF model is similar, although a 
little slower bringing the cooler air into our area with a secondary 
cold front dropping into the region as shortwaves continue to rotate 
through the upper level trough over the Great Lakes region.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1239 PM CDT Thu Jun 26 2014

CU field is in the process of developing, especially along the
Mississippi River where weak trof/surface convergence was noted earlier
this morning. Have added some VCSH for the next 1-2 hours at UIN,
STL, and CPS based on new echo development during the last 20
minutes, and will obviously have to watch additional development
of hit and miss convection during the afternoon for possible
inclusion in TAFs. This diurnally-driven convection threat should
dissipate by early this evening, leaving just a few mid and high
level clouds for the overnight hours. Believe any threat of overnight
convection will primarily be near/north of KUIN with greatest
coverage to the north of our area, although will be fine-tuning
this as upstream trends hopefully become a bit more obvious.

Specifics for KSTL: Sct-bkn CU aoa 5kft expected this afternoon
along with hit and miss convection. Radar indicating showers now
forming 5-10NMI ne of the airport so have added VCSH for the next
hour or so, and will obviously have to keep an eye on radar trends
for possible adjustments to the this threat during the afternoon,
including the threat of thunderstorms directly impacting the
terminal complex. Storm threat should dissipate early this evening
with loss of heating, with just a few mid-high clouds expected
during the overnight hours. 

&&

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

$$

WFO LSX