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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 64 °
• Low: 45 °
• Partly Cloudy

• Friday
• 
• High: 68 °
• Low: 55 °
• Clear

• Saturday
• 
• High: 73 °
• Low: 50 °
• Chance of T-Storms

• Sunday
• 
• High: 73 °
• Low: 55 °
• Partly Cloudy

• Monday
• 
• High: 75 °
• Low: 63 °
• Mostly Cloudy

Area forecast discussion...updated aviation 
National Weather Service St Louis MO 
1141 PM CDT Wednesday may 22 2013 


Update... 
issued at 841 PM CDT Wednesday may 22 2013 


Isolated showers...mainly light can still be expected across northestern 
MO and west central Illinois for the remainder of the night as a weak shortwave 
over eastern Nebraska drops southeastward through northestern MO and west central Illinois late 
tgt. More significant showers just ahead of a cold front extending 
from a surface low near Ord SW through sar and familiar should remain east-southeast 
of our forecast area as the front continues to move slowly southeastward. 
Although much of the cumulus and stratocumulus clouds have dissipated 
across southeastern MO and southwestern Illinois with loss of daytime heating...low-mid 
level clouds will continue to rotate southeastward through at least the 
northern half of our forecast area for the rest of tgt...behind the 
upper level low/trough and associated surface low over the Great Lakes 
region. Cooler low temperatures are forecast for tgt compared to 
the previous night...and slightly below normal for late may due to 
weak low level cold air advection behind the cold front and lowering surface dew 
points. The 00z Thursday NAM model run drops the 8 degree c 850 mb 
isotherm southeastward into southeastern MO and southern Illinois by 12z Thursday. 


Gks 


&& 


Short term...(through late tonight) 
issued at 314 PM CDT Wednesday may 22 2013 


A few showers that popped up along and ahead of a reinforcing cold 
front will continue to gradually move eastward...and any lingering 
showers should taper off quickly after sunset this evening with a 
loss of diurnal heating. The large low continuing to spin over the 
upper Midwest/Great Lakes will act to keep much of the region 
under partly to mostly cloudy skies tonight...thus have not gone too 
far below guidance on tonight's lows...which will generally be in 
the low to middle 50s across the area. Observation today over eastern and 
southeastern Nebraska have indicated some pockets of light 
rain/drizzle occurring on the back side of the low...thus cannot 
rule out some light precipitation over the northern tier of the County Warning Area 
as the low begins to finally lift northeast...mainly during the late 
overnight hours to just before daybreak. 


Phillipson 


Long term...(thursday through next wednesday) 
issued at 314 PM CDT Wednesday may 22 2013 


Thursday through Friday night...vorticity maxes moving across the area tomorrow 
may support isolated showers however the timing of the vorticity maxes 
are currently forecast to be temporally out of sync with diurnal heating 
which would tend to limit precipitation coverage. Some cloud cover should 
persist tomorrow within cyclonic flow aloft in the wake of a 
departing low pressure system. A strong surface high then builds into 
the Midwest and brings cooler air to MO/IL...effectively pushing a 
frontal boundary in southern MO/northern Arkansas southward as a cold front. The coolest overnight 
lows out of the next several days will probably occur late 
tomorrow night/early Friday morning. Temperatures should remain 
seasonably cool on Friday under the influence of cool Ely surface flow. 
Generally dry conditions are expected through Friday night however 
nocturnal convection driven by the low level jet may clip the northwestern County Warning Area on 
late Friday night. 


Sat through Tuesday...surface winds will gradually become southerly across the County Warning Area 
around the back side of the surface high once it shifts farther eastward. A 
developing low over the plains will reorient a baroclinic zone such that 
it stretches through eastern Kansas and western MO as a warm front. Temperatures will 
warm up over the weekend as this boundary lifts into central MO with the 
temperature increase aided by the strong sun angle at this time of 
year. Models are hinting at a few ill-defined vorticity maxes moving 
across the area over the weekend which may support scattered 
thunderstorms. Additionally...upstream nocturnal mesoscale convective system development may also 
affect our area this weekend...either as decaying remnants moving 
into the County Warning Area or by generating an mesoscale convective vortex which focuses thunderstorms and rain development 
during the following afternoon. Pop12 climatology for this time of year 
is around 30 percent and that looks reasonable given the lack of 
well-defined features to focus precipitation development and the uncertainty 
regarding the effects of upstream mesoscale convective system activity. The upper air 
pattn over the central part of the country will shift from ridging 
to SW flow by the middle of the week after a shortwave moves into 
the southwestern Continental U.S.. 


Kanofsky 


&& 


Aviation...(for the 06z tafs through 06z Thursday night) 
issued at 1130 PM CDT Wednesday may 22 2013 


Trough currently over Iowa will move slowly south...reaching KUIN 
12-14z and kcou and the St. Louis metropolitan tafs 15-18z. MVFR clouds 
currently over Iowa will move south with the trough...and have 
gone with 1500ft ceilings at KUIN and 2000ft at kcou and the St. 
Louis metropolitan tafs. There are some IFR ceiling in Iowa...so couldn't 
rule out these lower ceilings...particularly at KUIN. Isolated 
-shra is also possible...with the best chances at KUIN...so have 
maintained vcsh there. West winds will veer northerly behind 
trough...and then northeasterly by tomorrow evening as skies clear. 


Specifics for kstl...expect trough to pass through the terminal 
around 18z causing winds to veer from the north. Ceilings will 
lower into the 2000-3000ft range by middle-morning before improving 
back to VFR late in the day. 


Britt 


&& 


Lsx watches/warnings/advisories... 
MO...none. 
Illinois...none. 
&& 


$$ 


Weather forecast office lsx