Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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

082
FXUS63 KLSX 192344
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
644 PM CDT Sun Mar 19 2017

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 340 PM CDT Sun Mar 19 2017

Scattered convection continues to shift eastward from central to
eastern MO this afternoon.  This activity is in an areas of 850 mb
warm air advection, theta-e advection, and moisture convergence on
the nose of a modest southwesterly low level jet.  This activity
should weaken with most of it dissipating by early evening.  More
elevated convection is expected to develop later this evening and
overnight as a stronger low level jet ramps up across northern MO.
There is still uncertainty as to the location of this convection
with most of the models, particularly the high resolution CAMs
keeping most of the convection north-northeast of our forecast area
tonight.  The operational GFS model looks too far south with its QPF
tonight.  For now will just go with scattered convection mainly
across northeast MO and west central IL late tonight.  Could not
rule out isolated hail in the stronger cores due to favorable lapse
rates and vertical wind shear.  With low level warm air advection
along with southerly surface winds and gradually rising surface dew
points temperatures will fall this evening, but then become nearly
steady or rise slightly overnight.  Most of the convection on Monday
should be east of the Mississippi River as the low level jet weakens
and veers.  A cold front will be dropping southward through our area
on Monday, but there will be some capping/CIN over MO and the
moisture profile will be more favorable for convection in IL ahead
of a weak shortwave.  Highs on Monday will be unseasonably warm, 10
to 20 degrees above normal, with the warmest readings across central
and southeast MO where the least cloud cover is expected along with
the highest 850 mb temperatures.

GKS

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 340 PM CDT Sun Mar 19 2017

(Monday Night-Saturday)
   The cold front over or just south of the St. Louis metro will
push southward to the Missouri Bootheel by Tuesday morning. This
will usher in slightly cooler and drier air to the area. A shortwave
pushes through the area Tuesday providing chances for showers with a
few thunderstorms south of St Louis.  High pressure will provide a
small break on Wednesday. There is a bit of uncertainty with the
system that will impact the area late this week into the weekend.
The GFS/ECMWF has displayed some timing and placement issues. That
being said decided to go with a GFS/CMC solution for this forecast.
A warm front will move up from the south ahead of the cold front in
the central plains on Thursday. This will provide chances for
showers and thunderstorms during the morning hours before the warm
front pushes north of the area. A cold front will slowly push
through the area Friday with chances of showers and thunderstorms on
tap through Saturday.

Kelly

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 626 PM CDT Sun Mar 19 2017

SPECIFICS FOR KCOU: VFR conditions are expected for the first 0-6
hours, but isolated SHRA/TSRA are possible after 04z. A broad area
of MVFR cigs should develop and reach the terminal during the
morning hours and then persist until after a cold front has moved
through the region. Initially southeast winds will gradually veer
ahead of the approaching cold front and become westerly to
northwesterly after fropa.

SPECIFICS FOR KUIN: VFR conditions are expected for the first few
hours of the TAF period, but a developing low-level jet will
support scattered SHRA/TSRA near the terminal after 05z. A broad
area of MVFR cigs should reach the terminal during the morning
hours and persist until after a cold front has moved through the
region. Initially southeast winds will gradually veer ahead of the
approaching cold front and become westerly to northwesterly after
fropa.

SPECIFICS FOR KSTL, KSUS, KCPS: A brief period of MVFR cigs was
occurring at St. Louis metro area TAF sites at TAF issuance, but
satellite imagery shows that improvement to VFR is imminent. A
southwesterly low-level jet will develop and increase overnight,
leading to LLWS conditions after 06z. A broader area of MVFR cigs
should reach the terminals by mid-morning and persist until a cold
front moves through the region during the afternoon. Initially
southeast winds will gradually veer ahead of the approaching cold
front and become westerly to northwesterly after fropa.

Kanofsky

&&

.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.