Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 190008
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
608 PM CST Wed Jan 18 2017
.SHORT TERM... (Through Late Thursday Afternoon)
Issued at 325 PM CST Wed Jan 18 2017
Forecast is still on track that showers and a few thunderstorms will
move into the area late tonight and tomorrow.
Low clouds broke up across the area today only to be replaced by mid
and high clouds that are streaming northward ahead of a dual upper
low currently over western Kansas and New Mexico. This moisture
stream will continue to cause clouds to lower and thicken across the
area through the evening hours. The chance for showers will
increase by late this evening over southeast Missouri as moisture
convergence increases on the nose of a low level jet underneath
increasing mid level ascent ahead of the upper low. The chance of
for showers will spread northward and increase across the area
overnight into Thursday morning as the upper low moves eastward.
The greatest chance for showers and highest rainfall totals will
be across southeast Missouri into southern Illinois where the
strongest low level forcing and precipitable moisture will be.
There will still some potential for thunderstorms tomorrow as
lapse rates steepen with the upper low. The chance of rain will
begin to taper off from west to east late in the day as the
forcing lifts eastward.
Temperatures will show little diurnal swing the next 24 hours
because of the clouds and the rain. They are a combination of
compromise MOS values and SREF 2 meter temperatures.
.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 325 PM CST Wed Jan 18 2017
Amplified weather pattern will remain over the CONUS from Thursday
night through the end of the forecast period on Wednesday. The main
feature of this pattern will be the longwave trof now off the west
coast of North America. This trof will dig across the western
states remaining in place through early next week. Persistent south
to southwest flow over the region will keep temperatures well above
normal. In fact, the warmest day in the upcoming stretch looks to
be Saturday with highs in the low to mid 60s which is pushing 30
degrees above normal for mid to late January.
Several shortwaves will rotate around the base of the persistent
western trof and eject northeast across the Plains. These waves
combined with moisture convergence on the low level jet will keep a
persistent chance of showers to the area at least through Sunday
night and into Monday morning. The pattern begins to shift Monday
night and Tuesday as the longwave trof finally moves east into the
Great Plains. Current indications are that Tuesday will be dry but
the chance of showers will return Tuesday night as ridging ahead of
the longwave shifts east and southwest flow returns.
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 549 PM CST Wed Jan 18 2017
Surface ridge over the OH and TN Valley regions will continue to
shift eastward. Mid-high level cloudiness will continue to spread
through our area ahead of a slow moving upper level low over the
central Plains. Low level moisture and cloudiness will advect
northward into the taf sites late tonight and Thursday morning
with the cloud ceiling eventually dropping into the IFR catagory.
Visibilities will also lower due to a combination of fog and rain
or showers late tonight/Thursday morning. A weak southeast
surface wind will become more easterly on Thursday.
SPECIFICS FOR KSTL: Surface ridge over the OH and TN Valley regions
will continue to shift eastward. Mid-high level cloudiness will
continue to spread through our area ahead of a slow moving upper
level low over the central Plains. Low level moisture and
cloudiness will advect northward into STL late tonight and
Thursday morning with the cloud ceiling eventually dropping into
the IFR catagory. Visibilities will also lower due to a
combination of fog and rain or showers late tonight/Thursday
morning. A weak southeast surface wind will become more easterly
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 40 50 44 58 / 40 70 50 20
Quincy 35 44 39 52 / 10 60 60 20
Columbia 39 48 42 57 / 40 40 30 20
Jefferson City 41 49 42 58 / 40 40 30 20
Salem 39 51 46 57 / 30 70 70 20
Farmington 41 51 44 58 / 60 70 40 20