Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 201751
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
Issued by National Weather Service Kansas City/Pleasant Hill MO
1251 PM CDT Thu Apr 20 2017
.SHORT TERM... (Through Late Tonight)
Issued at 406 AM CDT Thu Apr 20 2017
Not a lot of change from the prev forecast thru tonight. Continued
warm trends for the ern half to two thirds of the CWA for today.
While there shud be a mostly bkn cloud deck today, the area shud
begin the day quite warm. With continued CAA tonight and clouds
clearing across nrn portions of the CWA, have trended aob the cooler
MOS while trending slightly warmer further south.
Mdl solns do not have a great handle on how precip will evolve
today. Expect ongoing SHRA with sct TS to continue thru the morning
hrs. TSRA shud develop ahead of the fnt, across ern and srn portions
of the CWA, by early afternoon with a weak CAP in place and heating.
Severe parameters are not great and think CAPE is overdone in many
mdl solns, wud expect pockets of greater instability to exist in
this area. With a weak CAP, storms shud initiate before much CAPE
can build, limiting the severe threat. That said, a threat will
remain with unidirectional hodographs allowing for storms to merge
with bowing segments possible. Believe main threat will be wind if
storms can become organized.
.LONG TERM... (Friday through Wednesday)
Issued at 406 AM CDT Thu Apr 20 2017
Models remain in pretty good agreement with upper level shortwave
over Central Plains sliding east, dragging surface low along stalled
boundary just south of forecast area. Rain chances to increase and
spread northward through out the day and into the overnight hours on
Friday. By Saturday, as system begins to lift off to the east
northeast, will see showers gradually taper off, especially by
Saturday evening. A few issues to deal with are qpf with this system
and temperatures, especially highs on Saturday. With front south of
forecast area, cloud cover, precipitation and northeast winds, it
will be a rather chilly rain with highs only in the upper 40s to mid
50s Saturday. Warmest temps will be across far northern portions of
forecast area where the lowest pops are. As for qpf, storm total
amounts of about an inch, along I70 corridor, to between 2 and 3
inches over southeast MO/southern IL can be expected. But it is over
a 3 day period, so feel that a flood watch is not warranted at this
Surface ridge to build in beginning late Saturday night, so will see
moderating temperatures for the remainder of the forecast period.
Temperatures to warm back up into the mid to upper 60s on Sunday,
then into the 70s by Tuesday and Wednesday. Extended models have
some timing and placement issues with the next system that will
approach the region by late Tuesday night, Wednesday. For now kept
what Superblend has with increasing chances of rain for this period.
.AVIATION... (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1249 PM CDT Thu Apr 20 2017
Hinted at some pockets of low end VFR or borderline MVFR CIGs with
the post frontal stratus, but actual MVFR prevailing clouds looks
unlikely. Terminals find themselves on the northern edge of the
precipitation late in the forecast period, so handled with VCSH for
now, but prevailing periods for rain will likely be needed later.
SPECIFICS FOR KSTL: FROPA taking place at the terminals which should
keep heavy rain away, but spotty showers are still possible
behind the front. Generally looking at VFR conditions with perhaps
a few patches of MVFR CIGs for the next few hours. Rain at the
terminals late in the forecast period is a bit uncertain, with the
heavier amounts remaining south of the St. Louis terminals. Could
see periods of showers late in the forecast period, but no
potential flight restrictions are forseeable at this point.
Updates to the rain activity and potential flight restrictions
will be addressed on upcoming issuance.
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 76 50 60 44 / 50 10 30 70
Quincy 70 44 59 42 / 40 5 10 40
Columbia 70 48 58 43 / 50 10 40 70
Jefferson City 71 49 59 44 / 60 10 50 70
Salem 79 50 60 45 / 70 30 40 70
Farmington 76 51 57 44 / 70 50 70 90