Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 220515

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1215 AM CDT Sun Apr 22 2018

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 316 PM CDT Sat Apr 21 2018

Initial wave of activity has been slowly diminishing as it tracks
across forecast area today, so just seeing some sprinkles. In the
meantime, the main system, a closed upper low over western KS to
slowly track to the east southeast tonight, lifting and deepening
associated surface low, currently over north central TX, as it
does this. Despite dry easterly flow at the surface, low level
moisture will be on the increase which will slowly offset the dry
air. Explicit models showing this as well, so pops to increase
tonight, with likelies as far north as I-70 corridor towards
daybreak. Then as initial shortwave exits, precip chances drop
south a bit, then another shortwave to bring precip chances back
north towards I-70 corridor during the afternoon and early evening
hours on Sunday. Otherwise, near normal lows tonight in the mid
40s to low 50s. Highs on Sunday, just a bit below normal,
especially along and south of I-70 due to cloud cover and
precipitation. The warmest temps will be across portions of
northeast MO and west central IL.


.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 316 PM CDT Sat Apr 21 2018

By Sunday evening, upper low will be centered over northern AR and
will continue its very slow track to the east northeast through
Monday night. So precipitation to persist across area then come to
an end by early Tuesday morning. Models are hinting at an even
slower pace for this system, so may need to keep precip chances
going on Tuesday, so will pass this onto mid crew.

Beyond that, dry wx to not persist for long as next system slides
southeast into area on busy northwest flow aloft. This system will
be more progressive, so rain to taper off by Wednesday afternoon.
Slightly cooler air to filter in for mid week. Then dry wx once
again, before a cold front tracks through beginning Thursday
afternoon through Friday morning with another round of light rain
before tapering off Friday afternoon.

Otherwise, temps to remain near or just below normal through the
week with daytime highs in the 60s and lows in the 40s.



.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1153 PM CDT Sat Apr 21 2018

Light rain showers are expected to spread east and northward
overnight and into Sun. KUIN will remain VFR and dry thru the
period with ely winds. Main question will be how far north the
precip will spread. Have delayed precip somewhat, but believe
that showers will move north to impact KCOU/KSUS/KCPS toward
sunrise. The precip shield shud sink back south thru the morning
hours, with a second round possible during the afternoon hours.
That said, can not rule out showers moving into and impacting the
terminals off and on throughout much of the day. A second
question will be how far north MVFR cigs will develop. Latest
guidance suggests MVFR cigs shud remain south of the terminals,
albeit not far south. Best chances for lower cigs are during the
Sun evening hours and will continue to monitor as new data
becomes available.

SPECIFICS FOR KSTL: Have backed off timing of onset of precip to
around sunrise. As this initial band dissipates, the focus shud
return south of the terminal. However, isod to sct showers shud be
possible thru the afternoon hours. Questions still remain how far
north MVFR cigs will develop. Have kept a sct deck in when MVFR
cigs are more likely, but lower cigs may remain south as dry air
continues to filter into the region.



Saint Louis     50  64  50  63 /  40  60  50  40
Quincy          46  64  46  64 /  10  10  10  10
Columbia        50  64  48  62 /  50  60  30  20
Jefferson City  51  62  49  63 /  60  80  50  30
Salem           49  64  51  62 /  30  60  50  50
Farmington      50  57  49  60 /  80  90  90  50




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