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Area forecast discussion...updated aviation 
National Weather Service St Louis MO
1158 PM CDT sun Jul 5 2015

Short term: (tonight through monday)
issued at 331 PM CDT sun Jul 5 2015

The evening looks rather tranquil across the region with
dissipating diurnal cumulus and a few high clouds filtering across the
area. The return of southerly low level flow has lead to warmer
temperatures today and greater moisture. Overnight there are
indications by the NAM and especially the rap that we may see some
spotty elevated showers and thunderstorms from south central MO
into east central and southeast MO in the near dawn hours, then
shifting east on Monday morning. A very weak peturbation in the
northwest flow aloft, and more importantly veering and strengthening
low-level flow in the 3000-7000 feet layer and attendant thermal and
moisture advection could generate some activity in the 07-15z time
frame. I have added some slight chance probability of precipitation to the forecast with
this in mind. Otherwise milder temperatures on tap tonight and a
rather warm day is on schedule for Monday. The models now all have
a bit slower progress with the cold front, not entering far
northwest MO until the 21-00z time frame. Given this slower speed
and lesser clouds expected with the forecast warm air advection regime, I expect
temperatures well into the 80s with a few spots around 90. We
could also see some spotty diurnally driven pulse storms in the
afternoon in the broad warm moist and unstable warm sector.


Long term: (monday night through next sunday)
issued at 331 PM CDT sun Jul 5 2015

Monday night into Wednesday still looks like a wet and stormy
pattern with widespread multi-day average rainfall totals of 2-4
inches. The biggest issue is just where the heaviest rainfall may
focus with the models having some growing differences with time
from Tuesday and beyond where the front may lie. The European model (ecmwf) has the
most agressive southward push early on then wavers the front
through the area late this week. Alternatively the GFS and NAM
both don't move the front as far south and then waver it Tuesday
night into Wednesday as surface waves move along it, finally
pushing north of the County Warning Area by Thursday evening. The region spanning
the frontal zone will be very moist and a broad region of deep low
level convergence will focus widespread showers and thunderstorms
with potential for heavy rain. We may ultimately need a Flash
Flood Watch once we can pin down the region a bit better.

Looks like precipitation chances will decrease into next weekend
with a return of Summer heat.



Aviation: (for the 06z tafs through 06z Monday night)
issued at 1142 PM CDT sun Jul 5 2015

Expect visibilities will continue to waver between 4-6sm for much of the
rest of the night. I think there's too much boundary layer wind to
support fog much thicker than that. However...noticed that kuno
came in with an 800ft ceiling at 0435z. Expect these IFR ceilings
to spread north-northeast through the rest of the night. Not
really sure how far northeast these low clouds will get before
sunrise, but areas south of the I-70 corridor are definitely under
the gun. Model guidance doesn't seem to be too interested in
spreading the ceilings as far north as I-70, but I can't rule it
out. Stratus and fog/haze should dissipate within 1-3 hours of
sunrise. There may also be some isolated showers or thunderstorms
after 12z Monday morning, but the wide-spread nature of this
precipitation makes it unlikely to affect any of the taf sites.
Remainder of Monday should be VFR with increasing south-southwest
flow...becoming gusty up to around 20kts in the afternoon. Some
scattered showers and thunderstorms are possible as well, most
likely over parts of southeast into east central Missouri. More
widespread thunderstorm activity will be possible on Monday
evening...mostly over northeast Missouri.

Specifics for kstl:

Expect visibility at Lambert to waver between 5-6sm for the rest of the
night. There is a chance that stratus which is in the process of
forming over south central Missouri may move up to overspread the
terminal by sunrise, but the chance this will happen does not look
high enough to put a ceiling in the taf at this time. Isolated
showers and possibly a thunderstorm may be in the vicinity of the
terminal during the morning...but like the stratus it looks like
probabilities are low that any precipitation will affect the
terminal. VFR flight conditions are expected Monday with
increasing south-southwest flow...becoming gusty in the afternoon.
There's a better chance of a thunderstorm in the afternoon...but
probably only 30% at best. VFR conditions are expected Monday
evening...but there's another chance of thunderstorms
overnight...timing and coverage are still uncertain so have left
mention out for now.



Lsx watches/warnings/advisories:


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