Area forecast discussion
National Weather Service Lincoln Illinois
134 PM CDT Tuesday Jun 18 2013
Discussion...
issued 133 PM CDT Tuesday Jun 18 2013
Latest model suite in reasonable agreement through the forecast
period as heights build and Summer moves into full swing.
Short term...tonight through Wednesday
Cold front at 18z extends from near Macomb...across Decatur...to
near Terre Haute. Instability along the front will likely be sufficient
for convective development later this afternoon and early evening along
the boundary where convergence and pooling dew points are
occurring. High pressure centered over the upper Great Lakes is
expected to continue to push the boundary southward through
tonight. Diurnal stability combined with drier air being advected
into Illinois should end rain chances by midnight.
Wednesday should be dry as high pressure dominates. Temperatures
should be cooler than normal. That will change as the week GOES on.
Long term...Wednesday night through Tuesday
Strong upper low in the northeast Pacific is expected to make
landfall across the northwest in the next 24 hours. As this
feature pushes East...Ridge should build ahead of it. Models are
consistent in developing rising heights across the Mississippi
Valley with rises of 160 meters at 500mb between now and Friday
evening. Temperatures should respond by moving above normal for
the late June. Low-level flow should also come around to south-
southwest by Friday allowing dew points to climb. Combination of
humidity and temperatures should bring heat index values between 95 and
102 across the area for the weekend and into early next week.
Biggest difference between the major models is whether ridging
will be sufficient to keep precipitation to our north. 00z European model (ecmwf)/12z NAM
are weakest and develop a pattern that is most conducive to
diurnal convection. 12z GFS/Gem is stronger with ridge and suggest
that any activity should remain isolated at least through the weekend.
Models in good agreement in redeveloping the upper ridge back over
the southern rockies by next Tuesday which will develop a little
more in the way of flow across Illinois and higher rain chances.
This transition may be a little fast and will keep Tuesday down to
slight chance for now but later shifts will have to watch carefully
for model trends.
Barker
&&
Aviation...
issued 1218 PM CDT Tuesday Jun 18 2013
Main concern for this taf set is timing of convection this
afternoon. Several high-resolution models pointing to scattered
storm development in central Illinois beginning around 19-20z and
most numerous during the middle to late afternoon hours. Have kept
thunderstorms in the vicinity wording at all taf sites for this afternoon...but have
focused on the kspi-kdec-kcmi corridor by adding tempo periods of
thunderstorms and rain and variable/gusty winds with the storms...as this area is
near a frontal boundary. Should see the convection fade out with
sunset. Drier northeast flow will clear out much of the area
overnight. Have held off on any overnight MVFR fog conditions...
but any areas that get excessive rainfall during the day may see
some develop although confidence is not high at the moment.
Geelhart
&&
Ilx watches/warnings/advisories...
none.
&&
$$
