Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 141804

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1204 PM CST Tue Feb 14 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 338 AM CST Tue Feb 14 2017

Mix of rain and some sleet currently over southeast Missouri and
southwest Illinois will exit the CWA by mid morning.  The shortwave
trough that is producing the precipitation will quickly move
southeast of the area this morning. Although some drier air will
advect in the low and mid levels, cirrus will continue to stream
northward today as an upper low moves from the Southern Plains into
the Lower Mississippi Valley.  Tonight still looks dry as the
Missouri and Illinois will lie under subsidence behind the

Highs today will be above normal given the already relatively warm
temperatures and RAP forecast soundings showing mixing up into the
900-850mb range.  This supports a compromise of the GFS and NAM MOS
temperatures.  Will continue to go with the compromise of the MOS
temperatures tonight when a tight surface pressure gradient will
keep winds up during the night.


.LONG TERM...  (Wednesday through Monday)
Issued at 338 AM CST Tue Feb 14 2017

Little change in the forecast for Wednesday through Monday for this
morning`s forecast.  Northwest flow through the depth of the
troposphere on Wednesday should make it the coolest day of the next
7.  Low level flow will turn back to the west and southwest again on
Thursday.  Southerly low level flow will persist through Monday.
Temperatures on Thursday will rebound into the mid 50s to low 60s.
Temperatures will continue to warm Friday and Saturday as the upper
level ridge currently over the West Coast moves into the Great
Plains and Mississippi Valley.  850mb temperatures rise to between
9C and 11C Friday.  850mb temperatures fluctuate between about 4C and
9c through the weekend but rise again to 12C or higher on Monday.
This will translate to temperatures in the mid to upper 60s and even
low 70s...perhaps even warmer.

Weather should be dry across most of the area until at least
Saturday/Saturday night.  There may be some light showers over
southern portions of the CWFA as a wave undercuts the large scale
ridging over the area Saturday and Saturday night...guidance prints
out very light qpf and there is sufficient low level moisture
convergence and dynamical forcing to support precip.  Have therefore
added some slight chance PoPs Saturday over the eastern Ozarks
Saturday as the wave passes.  The next chance for rain will come
Sunday night and Monday as the upper ridge shifts east into the Ohio
Valley.  850mb jet ramps up to 40-50ks by 12Z Monday forcing
moderate low level moisture convergence.  Latest model runs are
actually a little slower than previous runs with the onset of
precip, but have opted to only make modest changes to PoPs at this
time in case this is an anomaly and subsequent runs are faster


.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1202 PM CST Tue Feb 14 2017

Weak frontal boundary exiting south of taf sites, so VFR
conditions to prevail with northwest to north winds through
forecast period.

Weak frontal boundary exiting south of taf sites, so VFR
conditions to prevail with northwest to north winds through
forecast period.



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