Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 120259
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
959 PM CDT Fri Jul 11 2014
Issued at 951 PM CDT Fri Jul 11 2014
Overall theme to the fcst still appears to be on track. The first
batch of precip continues to weaken as it moves through cntrl IL.
Precip is currently dvlpng north of the warm front across NE NEB/SE SD
and NW IA. This activity should continue to expand over the next
several hrs and then slide ESE along the warm front into ern IA
and cntrl IL. Have trimmed back POPS some for tonight...esp prior
to 9Z. It looks like it will be well after midnight before any
significant precip makes it into the CWA.
.SHORT TERM: (Through Late Tonight)
Issued at 321 PM CDT Fri Jul 11 2014
Psuedo warm front currently stretching from northern Kansas across
northern Missouri into southern Illinois will lift northward tonight
and better defined across Nebraska, Iowa and north-central Illinois.
This boundary will also be the main focus for convection tonight
with lift provided by a veering west-southwesterly LLJ and a series
of weak mid-level impulses tracking east along the southern edge of
the westerlies. Model QPFs and convection allowing models all
generally agree that convection across eastern Iowa will take a more
southeastward turn overnight in response to veering flow aloft,
potentially impacting portions of northeast Missouri into west
central and south central Illinois. Warming aloft should generally
limit the westward extent into Missouri. Temperatures should be much
warmer tonight due to bouts of clouds, southerly winds and higher
.LONG TERM: (Saturday through Next Friday)
Issued at 321 PM CDT Fri Jul 11 2014
On Saturday, best chances of rain for our area will be over
northeast MO and west central IL as overnight complex dies out. Hot
and humid weather to return to the region with highs in the low
to mid 90s, and heat indicies approaching 100.
By Saturday night, main frontal boundary begins to slide south
into forecast area with chances of showers and thunderstorms on the
increase and expand south across rest of forecast area by Sunday.
Could see chances of severe weather through this period with main
threat being damaging winds. Best chances Saturday night will be
across far northern portions of MO and north half of IL as MCS
develops and tracks east along boundary. By Sunday, as front
continues to track south through region, will see steeper lapse
rates by afternoon with plenty of low level moisture, so could see
clusters or line segments develop. Lows through the weekend to
remain mild with low to mid 70s Saturday night and mid 60s to low
70s Sunday night. Highs on Sunday will be a bit cooler north due to
storms, clouds and cold front, in the mid 80s north to the mid 90s
Despite front moving south of forecast area by Sunday night,
activity to persist as strong upper level shortwave slides into the
Great Lakes region by Monday helping to trigger more showers and
thunderstorms along secondary cold front. Dry and cooler conditions
expected by Tuesday as strong surface ridge builds in. Highs to drop
into the 70s by Tuesday then begin to moderate a bit by the end of
the work week.
.AVIATION: (For the 00z TAFs through 00z Saturday Evening)
Issued at 626 PM CDT Fri Jul 11 2014
Primary concern for tonight is the possibility of thunderstorms
across northern Missouri into west central and southwest Illinois.
Expecting a complex of thunderstorms to develop tonight across
parts of Iowa and build southeast into northern Missouri into west
central Illinois. Additional development to the southwest across
central and southwest Illinois during the pre-dawn hours is also
likely, though it`s not clear how far to the west the
precipitation will build. VFR flight conditions are expected
outside of any heavier thunderstorms.
Precipitation could linger through mid-late morning across parts
of Illinois, but VFR flight conditions are expected to prevail
outside of areas of precip.
Specifics for KSTL:
Expect VFR flight conditions to prevail through the night and into
Saturday at Lambert. There is a slight chance that the western
edge of an area of thunderstorms might affect the terminal during
the pre-dawn hours, but best indications are that the
precipitation will stay east of the Mississippi River. The
earliest there could be rain at the terminal would be 09-11Z, so
will continue to watch trends and see what the 00Z model guidance
comes up with.