Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
417
FXUS63 KLSX 300927
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
427 AM CDT Thu Mar 30 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 334 AM CDT Thu Mar 30 2017

A slow-moving low pressure system will continue to influence the
region today and tonight. Due to the initially slow movement of
this system, parts of the LSX CWA will be in a favorable location
for severe thunderstorms today, especially across the eastern CWA
during the afternoon hours. The potential for severe
thunderstorms will shift eastward with time, and the eastern half
of the CWA (especially locations east of the Mississippi River)
will have a greater chance of experiencing severe weather through
the evening hours compared to the rest of the CWA.

Ongoing SHRA/TSRA early this morning will gradually move out of
the CWA, leaving several hours for air mass recovery before the
next round of convection develops ahead of an approaching cold
front associated with the aforementioned low pressure system.
Although there is some question about the amount of cloud cover
and resultant destabilization today, models still depict 500-1000
J/kg of CAPE across the eastern CWA in the presence of 40-50 kts
of 0-6km shear. This will be sufficient for severe thunderstorms.
The primary threats are hail and damaging winds. A few isolated
tornadoes aren`t entirely out of the question, especially if
enough clearing occurs and instability values are higher than
expected, but forecast 0-1km shear values of around 10-15kts are
fairly low. The potential for tornadoes is greater farther east
where 0-1km shear values are much more favorable.

Lingering precipitation behind the departing low pressure system
should exit the region overnight. Overnight lows will be around 10
degrees cooler than last night due to a cooler post-frontal air
mass.

Kanofsky

.LONG TERM...  (Friday through Wednesday)
Issued at 334 AM CDT Thu Mar 30 2017

Another disturbance will move onshore near the CA/OR border on
Thursday and settle into the southwestern CONUS on Friday as a
closed low pressure system. This feature then makes slow eastward
progress over the weekend, eventually approaching MO/IL. As has
been the case for the last few nights, the GFS, ECMWF, and GEM now
offer different solutions for the evolution of this feature and
for the evolution of the next 2-3 upstream disturbances. The
general consensus is that an active weather pattern will persist
through the middle of next week. Expect around 1-2 days between
the increased precipitation chances associated with these periodic
low pressure systems.

Kanofsky

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 135 PM CDT Wed Mar 29 2017

Scattered showers with MVFR conditions are expected during the
afternoon. Line of thunderstorms are expected to develop over
western Missouri this afternoon and move across the terminal
during the late afternoon and evening hours with IFR and MVFR
conditions. MVFR and IFR conditions with showers and scattered
thunderstorms will continue through the night. Additional
thunderstorms with MVFR conditions will be possible on Thursday.|

SPECIFICS FOR KSTL: Scattered showers will be possible with MVFR
conditions this afternoon. A line of showers and thunderstorms
with IFR and MVFR conditions. MVFR and IFR conditions with showers
and scattered thunderstorms will continue through the night.
Additional thunderstorms with MVFR conditions will be possible on
Thursday.|

Britt

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     68  45  54  41 /  80  50  10   0
Quincy          61  40  49  37 /  80  80   5   0
Columbia        59  42  54  40 /  70  60   5   0
Jefferson City  60  43  56  40 /  70  60   5   0
Salem           71  47  53  40 /  90  40  20   0
Farmington      66  46  58  40 /  60  40   5   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.