Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 210444
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1144 PM CDT Sun Jul 20 2014

.UPDATE:
Issued at 930 PM CDT Sun Jul 20 2014

Another clear/calm night in store with slowly increasing winds out
of the south across central/northeast Missouri overnight. Low
temperatures for now still look on track as dayshift forecaster
leaned toward cooler guidance across eastern Ozarks/southwest
Illinois where impacts of sfc ridge axis are still being felt.
Only real change to going forecast was to add some patchy fog
across those same areas where temps should approach or exceed
crossover temperatures due to light winds/clear skies...similar
conditions as observed this morning.

Gosselin

&&

.SHORT TERM: (Tonight through Tuesday)
Issued at 235 PM CDT Sun Jul 20 2014

The main weather story for the next few days will be the return of
summer heat. Southerly flow across the region today has brought
warmer temperatures and increasing moisture, with RH noticeably
higher today. This upward trend will continue through Tuesday as
the upper high/ridge currently centered in NM amplifies and builds
northeastward through the Nation`s midsection. Monday looks around
normal for this time of the year. Tuesday looks seasonably hot
with a pronounced low-level thermal ridge centered through the
northern half of the CWA with H85 temps of +22 to +24 degC, mid
levels temps of +12 to +14 degC and H5 heights of 594+ dm, all
supporting high temperatures well into the 90s. These warm
temperatures aloft are expected to effectively cap any surface
based storm development. We might need to keep an eye on a few
high-based showers at 10 kft or higher on Tuesday morning across
northern sections of CWA associated with a pocket of moisture
aloft and steep lapse rates.

Glass

.LONG TERM: (Tuesday night through Next Sunday)
Issued at 235 PM CDT Sun Jul 20 2014

The return of summer heat will be short-lived however. A new
longwave trof will develop across the eastern U.S. during the
later part of the upcoming week in association with large scale
amplification across the Canada into the northern portion of the
U.S., with an initial short wave trof digging through the Great
Lakes-mid/uppper MS Valley late Tuesday into Wednesday. This wave will
send a cold front across the region in the Tuesday night/Wednesday
time frame. Height falls/cooling aloft, convergence along the
front, and good moisture and instability should be sufficient for
at least scattered showers and thunderstorms. Cooler temperatures
and dry weather will then prevail in the wake of the front
Thursday/Friday as surface high pressure dominates the region. The
combination of the northward returning front on Friday night and
then another cold front Saturday-Sunday will bring a return of
showers and thunderstorms.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1123 PM CDT Sun Jul 20 2014

High pressure slowly shifts east through the forecast. Southerly
wind pick up just a bit with afternoon cumulus the highlight. Some
morning fog possible at SUS and CPS, but current temp/dew pt
spreads are 5 - 10 degrees more tonight so will leave out.

Specifics for KSTL: VFR with light southerly wind.

JPK

&&

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

$$

WFO LSX






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