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
000
FXUS63 KLSX 182307
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
607 PM CDT THU AUG 18 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 341 PM CDT Thu Aug 18 2016

Isolated to scattered showers and thunderstorms are possible
across the southern CWA overnight due to increasing moisture and
ascent, but widespread coverage is not anticipated attm.

Kanofsky

.LONG TERM...  (Friday through Next Thursday)
Issued at 341 PM CDT Thu Aug 18 2016

There are three primary forecast concerns over the next 7 days:
thunderstorm chances for Friday through Saturday night, cool
overnight lows on late Sunday/early Monday, and thunderstorm
chances for the middle part of next week.

A strong cold front will approach the region tomorrow and
tomorrow night before moving through the CWA on Sat/Sat night.
Large-scale lift ahead of an upper vort max will support
widespread coverage of showers and thunderstorms, especially on
Friday night and Saturday. Models depict 20-30 kts of 0-6km shear
across parts of southeastern MO and southwestern IL on Sat
aftn/eve, which may be sufficient for a few strong to severe
thunderstorms depending on instability.

A surface high builds in behind the front and ensures quiet wx
conditions for Sun/Mon. Highs on Sunday may struggle to reach 80
degrees F within the cooler post-frontal air mass. The current
forecast highs for Sunday (upper 70s) are 5-10 degrees below
average. The center of the surface high should be located nearly
overhead by 12z Mon, and the combination of nearly clear skies and
light winds should produce favorable radiational cooling
conditions on Sunday night/early Monday morning. The combination
of good radiational cooling conditions along with a cooler
post-frontal air mass should bring overnight lows down into the
mid to upper 50s across most of the region, which is roughly 5-10
degrees below average.

The surface high moves slowly eastward early next week and
southerly return flow commences over the plains, sharpening a N-S
boundary which eventually lifts northeastward as a warm front on
Wed. Models also depict a stalled cold front or quasistationary
front somewhere over the region during the middle and late part of
next week. A few weak shortwaves will move across the area during
the middle and late part of next week and may interact with the
sfc boundaries to produce periods of showers and thunderstorms.

Kanofsky

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 549 PM CDT Thu Aug 18 2016

Diurnal cumulus clouds will dissipate early this evening with
loss of daytime heating. Mainly just some high level cloudiness
for the St Louis metro area as persistent high level clouds
continue to stream northeastward through southeast MO and
southwest IL. South-southwest surface wind will become light
later the evening. There may be some fog late tonight/early Friday
morning, particularly at CPS and SUS, although the MOS guidance
appears a little overdone with its forecast of stratus and fog.
Scattered diurnal cumulus clouds is expected again late Friday
morning and afternoon. There may also be isolated showers/storms
Friday afternoon, but for now will keep the tafs dry. Surface
winds will be southerly on Friday with the surface ridge southeast
of the region and a cold front approaching from the northern
Plains.

SPECIFICS FOR KSTL: Diurnal cumulus clouds will dissipate early
this evening with loss of daytime heating. Mainly just some high
level cloudiness as persistent high level clouds continue to
stream northeastward through southeast MO and southwest IL.
Southwest surface wind will become light later the evening. There
may be some fog late tonight/early Friday morning, although the
MOS guidance appears a little overdone with its forecast of
stratus and fog. Scattered diurnal cumulus clouds is expected
again late Friday morning and afternoon. There may also be
isolated showers/storms Friday afternoon/evening, but for now
will keep the STL taf dry. Surface winds will be southerly on
Friday with the surface ridge southeast of the region and a cold
front approaching from the northern Plains.

GKS

&&

.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.