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Area forecast discussion 
National Weather Service Lincoln Illinois
728 PM CDT Monday Jul 27 2015

Update...
issued at 728 PM CDT Monday Jul 27 2015

Line of thunderstorms that developed along a stationary frontal
boundary late this afternoon continues to push eastward into
west-central Illinois early this evening. 00z/7pm radar imagery
shows the leading edge of the precipitation extending from Burlington,
Iowa to just north of Saint Louis. The storms are moving away from
the best instability and as the sun sets, weaker instability
further east into Illinois will wane as well. As a result, am
expecting the convection to weaken and completely dissipate before
midnight. Based on current radar trends, have increased probability of precipitation to
likely across the west/SW County Warning Area this evening...tapering down to chance
probability of precipitation along the I-55 corridor. Further east, am expecting dry
conditions across the remainder of the area. Once the storms fade,
dense cirrus clouds will likely linger for much of the night. This
will tend to limit the potential for dense fog overnight. Will
still keep patchy fog in the forecast though, as airmass remains
quite moist and winds will become light/variable in the vicinity
of the front.

&&

Short term...(tonight)
issued at 255 PM CDT Monday Jul 27 2015

Remnants of stationary boundary draped across the Midwest this
afternoon. An upper ridge building in from the western Gulf Coast
up through the upper Midwest and western WI. Last nights fog
managed to keep a lot of moisture in the boundary layer this
morning, only elevating it to 2k-3k feet with the cloud deck this
afternoon. With cumulus redeveloping in any gaps in the cloud cover,
most areas have been mostly cloudy throughout the day, limiting the
amount of diurnal mixing out of the low level dewpoints. Rich moisture
and dewpoints in the low to middle 70s this afternoon will lend itself
to another muggy and warm evening. Patchy fog possible later
tonight towards morning as well. May need to upgrade mention to
dense fog...but will know better once the xover temperatures are
established.

Long term...(tuesday through monday)
issued at 255 PM CDT Monday Jul 27 2015

Weak convergent boundary will still be located in southwest part of
County Warning Area Tuesday so will keep a slight chance of precipitation in the afternoon
along that an just ahead of the approaching cold front in the
northwest. Models very similar with the frontal boundary and have
trended quicker with the front. So have chance probability of precipitation sooner for Tuesday
evening with continued chance probability of precipitation for Wednesday. With front coming
through sooner...precipitation will end sooner so have no probability of precipitation for Wednesday night.
Dry weather will move into the area for Wednesday night through the end of
the week as high pressure builds into the region from the west. This
high pressure will also bring lower/drier dewpoints into the area with
westerly winds. As the ridges shifts east...another frontal system
will push toward the area for the weekend. This front is forecast to
be slow moving and elogated from west to east...almost parallel with
the flow. So think best chance of precipitation will be sun and Sunday night.
So will have chance probability of precipitation for time period.

With southerly flow ahead of an approaching front...expecting temperatures
to get quite warm tomorrow...looking at upper 80s in the northeast
to lower 90s in the west and southwest. The only possible negative
to temperatures getting this warm will be if there is any scattered
convection of convective blow-off clouds over the area. Dewpoints
are in the lower to middle 70s today and upper 70s are not that
far away and should be in the area tomorrow. So hot temperatures combined
with upper 70s dewpoints will result in heat index values of 100 in
the east to 110 in the west. So will be issuing a heat advisory
for most of the area...to not include 4 counties in the east. With
the front coming through sooner on Wednesday...temperatures and dewpoints
in the southwest will not get high enough to warrant a
continuation of the advisor through Wednesday. Beyond the front on
Wednesday...temperatures will drop back down into the 80s with dewpoints back
into the 60s.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 648 PM CDT Monday Jul 27 2015

A line of thunderstorms that developed along a stationary frontal
boundary late this afternoon has pushed slowly eastward and is now
crossing the Mississippi River into west-central Illinois. The
storms are moving away from the best instability and are expected
to diminish considerably over the next couple of hours. Based on
current radar trends...think a few showers may make it as far east
as kpia and kspi between 02z and 04z. Have included a tempo group
for -ra at those sites accordingly...with dry conditions further
east. Once the showers fade...a blanket of thick cirrus clouds
will persist through the overnight hours. Due to the cloud
cover...do not think dense fog will re-develop late tonight as it
did last night. Have reduced visbys to around 2-3sm at all
terminals after 08z...but have removed mention of dense fog. Once
any early morning fog dissipates...mostly sunny and dry conditions
are expected on Tuesday with winds becoming S/southeast at 5-8kt.



&&

Ilx watches/warnings/advisories...
heat advisory from 1 PM to 8 PM CDT Tuesday for ilz027>031-
036>038-040>044-047>054-056-061>063-066>068-071>073.

&&

$$

Update...Barnes
short term...hjs
long term...auten
aviation...Barnes

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