Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 270016
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
716 PM CDT Wed Apr 26 2017
.SHORT TERM... (Through Late Thursday Afternoon)
Issued at 126 PM CDT Wed Apr 26 2017
Deep upper trof will swing thru the region this evening with the
cdfnt pushing sewd thru the area. Ongoing TSRA are expected to
continue along the sern CWA border for the next few hours with
mainly a wind threat.
Expect precip event to transition to a stratiform RA with sct to
isod TS spreading over much of the CWA. Some areas of heavy
rainfall will be possible this evening as the sfc low approaches
the area. Have held off any flood headlines for now, but will need
to monitor how the event unfolds.
Thurs is expected to remain dry with a weak sfc ridge building
into the region ahead of the next approaching system. Have trended
temps twd the warmer guidance with clouds expected to clear out
during the morning hours. Have not gone above the warmer guidance
due to at least some clouds expected to spill back into the region
during the afternoon.
.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 311 PM CDT Wed Apr 26 2017
After a brief break in the precipitation, next in a series
shortwaves will slide through region beginning late Thursday night.
This shortwave in conjunction with decent moisture and convergence
along a developing warm front will help overrunning precipitation
develop and slide northward across forecast area.
Warm front to lift north of forecast area by Friday afternoon,
though will see scattered showers and storms persist in warm sector.
Will see a decent temperature gradient on Friday due to frontal
boundary with highs ranging from the low 60s north to the upper 70s
Then frontal boundary begins to sink back south across forecast
area, stalling out along I-44 corridor Friday night. In the
meantime, closed upper low over southwestern U.S. to begin lifting
northeast towards forecast area. Will see several rounds of heavy
rainfall due to increasing moisture advection ahead of this system
Friday night through Sunday. Still some differences between the
models concerning qpf with this system. Will go with a blend with
widespread totals of 2-5 inches expected from NE MO to SE MO with
higher totals possible across the eastern Ozarks. Since there is
still some uncertainty with amounts and location of heaviest
rainfall, will only update ESF product and not issue any flood
watches at this time. As for any severe chances, broad low level
jet to develop Friday night and enhance convergence along and
north of stalled frontal boundary. So could see elevated
convection, mainly along and south of I-70 corridor Friday night.
Will continue to see wide range of temperatures due to frontal
boundary and precipitation.
Closed upper low to finally lift out of southern plains and lift
deepening surface low north northeastward towards Great Lakes
dragging the cold front through region on Sunday. Precipitation
chances to taper off Sunday night, though will see some wrap around
showers on backside of system late Sunday night/early Monday morning
before coming to an end.
Another brief break in the precipitation Monday afternoon through
Tuesday morning before next system moves Tuesday afternoon through
Wednesday. Coolest temps will be on Monday with highs in the mid 50s
to mid 60s, then moderate back into the mid 60s to low 70s by
Tuesday and Wednesday.
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 710 PM CDT Wed Apr 26 2017
Rain and IFR CIGs will prevail for the TAF sites for much of this
evening, with gradual improvement and rain ending from west to
east. VFR is then expected to prevail thru the daylight hours of
Thursday and continue into Thursday night as clouds increase and
rain chances gradually ramp up late. Winds will shift to W-NW
shortly if not already so and will continue for much of Thursday
before becoming light-variable with a surface RIDGE building in.
SPECIFICS FOR KSTL: IFR CIGs expected shortly and with
intermittent VSBYs in IFR from rain to continue for much of the
evening and early overnight. Improvement to VFR by daybreak
Thursday with VFR to prevail thereafter.