Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 220446
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1146 PM CDT Tue Apr 21 2015
Issued at 643 PM CDT Tue Apr 21 2015
A small update to the forecast for this evening to remove PoPs
outside of srn portions of the CWA, where PoPs were increased based
on latest RADAR trends and mdl guidance. Still expect area of RA
over IA to move swd into the area. A s/w shud help regenerate some
isod to sct TSRA across srn portions of the CWA late tonight, but
coverage shud be less than current activity.
Also lowered temps a few degrees based on the latest mdl guidance.
Believe temps will remain above the freezing mark, but is expected
to be close across nrn portions of the CWA. Currently do not
anticipate frost as winds shud help prevent it. However, with
clouds clearing out, RA expected this evening, frost can not be
completely ruled out. Will continue to monitor this evening and
update as needed.
.SHORT TERM: (Through This Evening)
Issued at 237 PM CDT Tue Apr 21 2015
Cumulus field continues to increase across southern Missouri this
afternoon with a few storms developing along a weak convergence
zone that stretch across the Ozarks. Can`t rule out a few reports
of hail or wind with these isolated to widely scattered
thundershowers but beleive threat is very small for widespread
impact. Othwerwise, breezy condtions will continue with west winds
gusting to 30 MPH at times.
.LONG TERM: (Wednesday through Next Tuesday)
Issued at 237 PM CDT Tue Apr 21 2015
The weather pattern is more reminiscent of winter, than
spring, across the center of the CONUS this afternoon with a deep
closed upper level low spinning across the Upper Peninsula of
Michigan and accompanying trof stretching far and wide from the
northern Plains to New England. A shortwave rotating south-southeast
on the resultant northwest flow aloft across the lower Missouri and
middle Mississippi River Valleys will bring another cold front south
across the CWA tonight. While a few showers are possible with the
front, the bigger story will be the continued below normal
temperatures that will be with us through at least Thursday morning.
High temperatures will struggle to get out of the 50s again on
Wednesday and frost is looking more and more likely for Thursday
morning. Will include patchy frost area-wide late Wednesday night
into Thursday morning for now and let later shifts determine need
for any increase in coverage and potential headlines. Would be far
more confident if cloud cover was going to be completely absent
during the period, but middle and high level clouds could start
edging back north overnight and limit coverage of frost.
Aforementioned cloud cover returning to the area will be in response
to rising heights as the next storm system that will affect our
region begins to approach from the west. This system has Pacific
origins and will be somewhat undercutting the predominant upper
level trof that currently encompasses the western 2/3rds of the
CONUS. Models are beginning to converge on the track of the surface
low (just to our south) and all indicate a very good chance of
measurable rain heading into the first half of the weekend. Have
continued the trend of slowly increasing PoPs for Friday afternoon
through Saturday morning with up to an inch of rainfall possible.
Northwest flow will re-establish itself across the region in the
wake of the low pressure system. High pressure, although temporary
should allow for one completely dry day this coming weekend on
Sunday. It appears that a series of upper level disturbances will
bring renewed chances of showers to the area Sunday night through
Tuesday with temepratures remaining below normal through the entire
.AVIATION: (For the 06z TAFs through 06z Wednesday Night)
Issued at 1145 PM CDT Tue Apr 21 2015
VFR conditions and NW surface winds will prevail thru the period.
It now looks as though the SHRA will not come to fruition for the
STL metro sites so have removed VCSH. Otherwise, gusty winds can
be expected for much of the daytime hours once again.
Specifics for KSTL: VFR with NW surface winds thru the period.
SHRA to remain to the north and or dissipate, so unless something
new forms nearer the front, VCSH is no longer needed. Otherwise,
gusty winds once again during Wednesday daytime.