Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service quadrant cities Iowa Illinois
656 PM CDT Tuesday Jun 30 2015

issued at 642 PM CDT Tuesday Jun 30 2015

Forecast still on track for the overnight period. Rain across west Iowa
has been slow to shift east. Believe that most of the rain wont
make it to the far SW until 06z Wednesday. Did increase the probability of precipitation
coverage slightly as a nod to the hires models that suggest areas
from i80 south could see rain with this system through tomorrow.
This could be overdone but decided to increase the probability of precipitation slightly
to represent that.


issued at 323 PM CDT Tuesday Jun 30 2015

12z upper air analysis has an 850mb low over lower Michigan with a weak
trough into southern Illinois. An 850mb warm front ran from northeast
Montana into central Nebraska. Satellite trends through middle
afternoon show a smoke layer high aloft with it most noticeable from
the Mississippi on west. Low clouds were across Wisconsin and moving
into northern Illinois while a band of low and middle level clouds were
along the Missouri River in the plains.

18z surface data has a weak trough from lower Michigan into northeast
Missouri. An inferred weak boundary ran from the eastern Dakotas
into western Missouri. Dew points were in the 50s across the Great
Lakes and upper Midwest with 60s from the Ohio Valley back into the


Short term...(this evening through wednesday)
issued at 323 PM CDT Tuesday Jun 30 2015

Quiet and dry conditions should be seen through sunset across the
area. The layer of smoke aloft is helping to suppress temperatures
just below the temperature needed to initiate convection. While one
cannot rule out a rogue shower developing prior to sunset...nearly
all of the area should remain dry.

Signals from the models point to another thunderstorm complex
developing this evening along the Missouri River and moving
southeast overnight. This storm complex should just brush the
southwest and South Quarter of the area after midnight.

Based on what the models are suggesting internally...the heaviest
rain should remain to the south and west of Kirksville Missouri.
However...Scotland and possibly the southwest corner of Clark
counties could get brushed with up to one half inch of rain.

If the thunderstorm complex would develop just a little further
west...the possibility does exist that rainfall in the far south and
southwest areas might be under 0.10 inches.

Wednesday morning...rain with possibly some thunderstorms should be
occurring south of an kotm to kgbg line. Boundaries left over from
the nocturnal storm complex combined with differential heating will
determine the potential for diurnal convection Wednesday afternoon.
Right now the better potential would be south of I-80.

Long term...(wednesday night through tuesday)
issued at 323 PM CDT Tuesday Jun 30 2015

While locations just southwest of the County Warning Area will remain wet and
active...there is a good indication that eastern Iowa and
northwest Illinois will finally be under the influence of Great
Lakes high pressure for several days...possibly all the way
through the upcoming weekend. There are significant model
variations to this...but over all we have growing confidence that
a more dry regime is in store for some time.

Rains Wednesday night will likely fall southwest of the County Warning the
European model (ecmwf) and GFS both show surface high pressure building over the
southern Great Lakes. This should provide a solid push of dry air to
keep any convection and rains south of our County Warning Area border...or more less
keep Missouri and southern Illinois in The Heart of the wet weather.

Thus...Thursday through Saturday should also be dry...with quite
mild air for early July. Highs in the upper 70s to lower 80s will
combine with lows in the lower 50s northeast to lower 60s southwest
Thursday and Friday to bring nearly ideal weather for most
activities. Dry...and just slightly warmer weather is expected into
Sunday. At which point...probability of precipitation will increase as a cold front is
expected to shift into the Midwest toward late Sunday and early
Monday. The GFS is active with the front with good moisture and
dynamics...while the European model (ecmwf) is much weaker...with a quick change back
to a regime of wet weather south over Missouri / southern Illinois
with dry Iowa and northern Illinois. Meanwhile the extended GFS
brings a large upper high into the Western Plains and eastern
rockies...placing a favorable heat dome there and aggressive mesoscale convective system
track through Iowa and Illinois. Thus...beyond Tuesday...very little
confidence is found in the forecast with respect to temperature or


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 642 PM CDT Tuesday Jun 30 2015

VFR conditions will dominate through the period. Haze associated
with smoke from fires in Canada will likely lead to visbys at or
around 6sm through the period. Could see some rain make it to
brl..this could lead to some of the haze being cleared out at brl
tomorrow. Do not think thunder will happen at brl...but there is
still a slight chance. Otherwise..winds will be light.


Dvn watches/warnings/advisories...


short term...08
long term...Ervin

National Weather Service Glossary of Abbreviations