Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 120909
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
409 AM CDT Sat Jul 12 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 321 AM CDT Sat Jul 12 2014

Thunderstorms have largely remained north of the area over
southern Iowa tonight, though over the past couple hours, a band
of showers has developed that extends from central Missouri
eastward through the St. Louis metro area, mainly associated with
the nocturnal low level jet. These showers may persist a couple
hours after sunrise before diminishing. A few stronger storms are
present over central Illinois, with coverage gradually increasing
into southwest Illinois along a weak surface boundary. Overall,
expect this activity to slowly diminish through the morning hours.

The main concern today will be the heat, as 850mb temperatures
rise to 20-22C, which translates to highs in the 90s area-wide,
with mid 90s expected generally along the Missouri River and into
the St. Louis metropolitan area. Humidity will be on the increase
as well, with afternoon dewpoints in the low 70s combining with
the hot temperatures to result in heat index values in the upper
90s to around 100 degrees. Much of the area should remain dry
once the morning`s precipitation tapers off. However, high
resolution models indicate the potential for some showers and
thunderstorms to develop over southeast Missouri and southern
Illinois this afternoon in an area of moisture convergence with
little to no cap. Have introduced slight chance pops for this area
during the late afternoon.

JP

.LONG TERM:  (Tonight through Friday)
Issued at 321 AM CDT Sat Jul 12 2014

By tonight, a low over western Ontario will begin to drop to the
northern Great Lakes and intensify, as the ridge over our area
begins to break down in response to the developing eastern CONUS
trough. Storms are expected to grow upscale into an MCS tonight from
eastern Nebraska through southern Iowa and into northern Missouri,
riding along the frontal boundary which will begin to sink south
overnight. While the slight risk of severe weather for tonight
remains just north of the CWFA as of the 06Z outlook, stronger
storms that occur overnight in northeast Missouri and west central
Illinois would have damaging winds as the primary threat.

During the day Sunday, the cold front will push southward, with
the chances for showers and thunderstorms overspreading the area
from north to south. Given convection expected tonight and
Sunday, high temperatures Sunday over northern portions of the
area will only reach the middle 80s, though the southern half of
the forecast area should have no trouble reaching into the low to
perhaps middle 90s once again. Widespread height falls over the
region on Sunday along with strong diurnal destabilization ahead
of the front should result in strong, to possibly severe storms,
which would likely produce damaging wind as a primary threat. The
cold front will continue to move south of the area by Sunday
night, and while a lull in precipitation is expected late Sunday
night and early Monday, a second, reinforcing cold front will once
again provide a chance for showers and thunderstorms Monday
afternoon and evening.

On Tuesday, cooler and drier air will filter into the area in the
wake of the cold front, and as surface high pressure builds in.
Temperatures will be well below normal Tuesday and Wednesday with
highs not expected to make it out of the 70s, and lows in the
50s. A moderating trend is expected for the last half of the work
week, with temperatures rising into the mid 80s by Friday, with
dry conditions expected to prevail.

JP

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1125 PM CDT Fri Jul 11 2014

Primary concern continues to be the chance for widely scattered
showers and thunderstorms...generally along and east of the
Mississippi River and across northeast Missouri and west central
Illinois later tonight. Short range guidance continues to develop
precipitation between 09Z and 11Z. Doesn`t look particularly
intense, except for perhaps some stronger storms pushing into
central Illinois toward daybreak. Went ahead and added vicinity
showers in the STL metro TAFs and Quincy since the guidance has
been very consistent. Precipitation may linger into mid-morning in
some spots. VFR flight conditions should prevail outside of any
precipitation, and are expected to prevail through Saturday.

Specifics for KSTL:

Primary concern continues to be the chance for widely scattered
showers and thunderstorms later tonight. Short range guidance
continues to develop precipitation between 09Z and 11Z, but doesn`t
look particularly intense in the STL Metro area. Went ahead and
added vicinity showers in the STL TAF since the guidance has been
very consistent. Precipitation may linger into mid-morning in
some spots. VFR flight conditions should prevail outside of any
precipitation, and are expected to prevail through Saturday.

Carney

&&

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

$$

WFO LSX






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