Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280502
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1202 AM CDT Sun Jun 28 2015

.UPDATE:
Issued at 922 PM CDT Sat Jun 27 2015

Most of the diurnally driven cu and showers have dissipated expect
for a few stragglers across the eastern Ozarks in Iron and Reynolds
County. These too should dissipate within the next hour or so.
Otherwise it appears to be a "cool" night with below average
temperatures. Clouds will begin to spread into northern sections
of the CWA overnight in advance of the next upstream northwest
flow short, however light winds and lots of clear time should
allow for some patchy radiational fog areawide.

Glass

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 325 PM CDT Sat Jun 27 2015

Sfc ridge will continue to build into the region this eve. Ridge
axis is progd to move swd thru the after Midnight tonight, bringing
swly winds to nrn and wrn portions of the CWA late tonight. Expect
high to possible mid level clouds to move into nrn portions of the
CWA near sunrise.

With the winds becoming swly late tonight, have trended slightly
warmer for these areas. For other areas, have trended aob the cooler
guidance for tonight, esp for ern Ozarks regions, with winds
becoming light under a clear sky. With much cooler temps expected,
can not rule out FG development overnight. The deep mixing today
will help cool dewpoints which may help prevent FG development.

Otherwise, expect SHRA that develops this afternoon to dissipate
quickly with sunset with the remainder of tonight dry.


Tilly

.LONG TERM:  (Sunday through Next Saturday)
Issued at 325 PM CDT Sat Jun 27 2015

(Sunday through Sunday Night)

Complex of showers and thunderstorms ahead of a potent northwest flow
vort max is expected to be just northwest of the forecast area early
Sunday morning. This area is expected to head into portions of
northeastern Missouri and west-central Illinois around midday.
Not sure whether or not area of showers/storms will sustain itself
through the morning hours but believe the area might as the
low-level moist/warm advection sustains itself. In any
event...strengthening of this complex...if it sustains
itself...would be likely along with new development downstream.
Supercells will be favored convective mode due to favorable
deep-layer shear (35-45 knots) along with a sufficiently unstable
airmass. As SPC noted in their discussion...NAM dewpoints and
therefore progged instability seems highly suspect but GFS MLCAPE
values would still support supercells. All forms of severe weather
will be possible late afternoon/early evening on Sunday though large
hail does seem like the predominate threat due to steep lapse rates
aloft. However...damaging wind gusts and isolated tornadoes also
possible. Highest threat of severe weather will be during the
afternoon hours across central and northeastern Missouri.

Initial supercells may collide/congeal into clusters by early
evening with damaging winds becoming more of a threat. Storms are
expected to gradually weaken as instability wanes by late evening.
By 0600 UTC, front will be nearly bisecting the CWA with chance PoPs
from 6-12 UTC.

Regarding high temperatures for tomorrow...went near or slightly
above warmer MET guidance as NW flow/clipper type disturbances are
notoriously known for yielding highs warmer than guidance south and
west of the track of the surface low.


(Monday through Saturday)

Quieter weather looks to be on tap for early next week with only a
slight chance of showers/storms Monday through Tuesday mainly east
of the Mississippi River. Another active period of weather looks in
store late Tuesday night through Thursday. Best chances of showers
and storms currently look to be on Wednesday and Wednesday night as
another shortwave embedded within northwest flow transverses the
mid-Mississippi Valley. Still some uncertainty of course with
regards to track/timing...but unfortunately this appears to be
another event which may produce some widespread rain amounts of a
couple of inches and exacerbate ongoing river flooding.

Temperatures will start off near seasonal norms Monday and Tuesday
due to deep mixing and westerly surface flow. Leaned above warmest
guidance each day due to these factors. By Wednesday and
Thursday...clouds/precip chances should yield below normal highs and
near normal low temperatures.

NW flow aloft looks to continue heading into the 4th of July weekend
with continued chances of showers/storms along with slightly below
normal highs.


Gosselin

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1147 PM CDT Sat Jun 27 2015

Specifics for KCOU, KUIN: Light winds and clear skies will
continue to promote light radiational fog across the region
overnight. Winds will continue to back ahead of an approaching low
pressure system, eventually becoming southwesterly and gusting to
around 20kts after 16z. Scattered SH/TS could affect KUIN before
18z, but precipitation chances at all TAF sites are higher after
21z because of favorable diurnal heating.

Specifics for KSTL, KSUS, KCPS: Light winds and clear skies will
continue to promote light radiational fog across the region
overnight, especially at KSUS where moderate rainfall earlier this
evening greatly increased the low-level moisture compared to
nearby TAF sites. T-Td spreads were high enough at KSTL at TAF
issuance to preclude a fog mention attm. Winds will continue
backing overnight ahead of an approaching low pressure system.
Expect scattered SH/TS to affect St. Louis metro area TAF sites
later this afternoon and into the evening.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






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