Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 270457
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1157 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 06z TAFs through 06z Thursday Night)
Issued at 1157 PM CDT Wed Apr 26 2017
Rain and IFR conditions prevail for most of the TAF sites will
begin to slowly retreat from SW to NE overnight and into early
Thursday morning, yielding VFR conditions thereafter. Dry wx is
also expected for much of the region once this current episode of
rain leaves late tonight with rain chances again on the increase
heading into Thursday night but low enough to preclude mention in
TAF. W-NW winds will continue for much of Thursday before becoming
light-variable with a surface RIDGE building in, and eventually
leading to an easterly flow later on Thursday night.
SPECIFICS FOR KSTL: IFR conditions and rain to continue until
around 09z with improvement to VFR and dry wx by daybreak
Thursday. W-NW surface winds until Thursday afternoon becoming
light-variable then easterly later on Thursday night.