Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 210457
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1157 PM CDT Wed May 20 2015
.SHORT TERM: (Through Late Tonight)
Issued at 327 PM CDT Wed May 20 2015
The shortwave causing today`s rain is nearly through the area, and
the last vestiges of the rain are now moving through east central
Missouri. Some lingering light rain may continue past 00Z in our
far eastern Illinois counties, but should be ending shortly
thereafter. Primary concern for tonight after the rain ends will be
clouds and temperatures. The clearing line is way up in South
Dakota and Minnesota and doesn`t look to be moving too fast. Think
we may see some faster clearing than what`s occuring now as the wave
moves further east and drier air funnles south into the region, but
the majority of the area will likely stay cloudy/mostly cloudy.
Stuck close to the colder guidance numbers for lows tonight. Lows
last night back in the plains were mostly in the low 40s and upper
30s so going with the colder numbers seemed reasonable.
.LONG TERM: (Thursday through Next Wednesday)
Issued at 354 PM CDT Wed May 20 2015
High pressure will build into the Mid-Mississippi Valley Thursday
and be a major influence on the weather through Saturday. Latest
model guidance keeps the CWFA dry through Saturday afternoon with
below normal temperatures Thursday and Thursday night, warming back
to near seasonal normals for Friday and Saturday. Southwest flow
aloft becomes reestablished by Saturday evening as another deep
trof sets up over the western CONUS. This trof will eject several
waves at us Saturday night through Monday night when it will finally
be pulled up into the mean flow and the pattern will de-amplify.
Periods of showers and thunderstorms look pretty likely from
Saturday night through Monday or Monday Night as a result of the
passing shortwaves. Can`t rule out more rain into the middle of
next week as well in zonal flow aloft as additional shortwaves move
across the area, though handled this with chance PoPs rather than
anything higher at this time. Temperatures look warm for Sunday
through next Wednesday with highs generally in the upper 70s to mid
80s and lows in the upper 50s and 60s due to prevailing
south-southwest flow bringing warm humid air up from the deep south.
.AVIATION: (For the 06z TAFs through 06z Thursday Night)
Issued at 1157 PM CDT Wed May 20 2015
The IFR CIGs have pushed to the south per the model consensus
earlier this evening and are doubtful to redevelop overnight as
additional dry air filters in from the north. Satellite shows
clouds breaking up to the north and we should expect more broken
cloudiness over the next several hours as the CIG trends generally
continue upward and should stay above 2000ft with few exceptions.
Only at UIN is an early overnight clearing of sorts expected and
this will probably result in fog formation and VSBY reductions
into the IFR range for a brief time. Clouds elsewhere should
preclude fog formation. Otherwise, VFR conditions are then
expected at the TAF sites shortly after daybreak Thursday onward.
Light NW surface winds will back from the W-SW late Thursday.
Specifics for KSTL: should be clear of IFR CIGs and fog should be
precluded as long as clouds stick around which currently they
appear that they will. Otherwise, improving conditions to VFR
shortly after daybreak Thursday and this will continue for the
remainder of the period.