Lake County SKYWARN

NWS Area Forecast Discussion

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Decoded

Original

Area Forecast Discussion
National Weather Service Chicago/Romeoville Illinois
934 AM CDT Friday july 30 2010

.Discussion,
332 AM CDT

A relatively dry airmass remains in place across the forecast area
early this morning with an expansive area of surface high pressure
centered across Lake Michigan and moving east.  Moisture channel
imagery shows a well organized trough over the st.  Lawrence Valley
with a northwesterly flow overhead and across much of the upper
Midwest and Great Lakes.  Several shortwaves are visible in the flow
and have been generating bands of convection off to the north and
west where deeper moisture resides.  Further west, two upper low
circulations are noted, one off the oregon coast and another to the
north over northern british columbia and alberta.  These are helping
to force ridging over the US and Canadian Rockies which will come
into play in the local weather into next week.

As noted above, several shortwaves will continue to traverse the
upper flow overhead.  Convection continues across southeastern
sodak, western Iowa, and southern Minnesota in conjunction with
an upper wave.  The surface high is fairly expansive and strong and the
convection will likely have a tough time making eastward progress as
it approaches the area.  The associated vorticity maximum does make it into
the area late this morning/early this afternoon but deep moisture
will be slow to increase.  Cloud cover will continue but precipitation
chances should remain low with the low levels remaining dry.  Have
refined timing of POP's through the day but will continue with slight
and low chance pops, mainly west, with the current activity still
making decent progress.  May be that only sprinkles or some scattered
light showers can make it into the far west this morning with the
bulk of the current complex remaining across southern Wisconsin.  Precipitation
chances will increase late this afternoon/early this evening as a
mid level baroclinic zone becomes established overhead with a well
defined trough appearing around h85.  Will continue with higher
chance POP's tonight.  Will not be able to completely remove POP's for
Saturday with the baroclinic zone/mid level trough moving slowly eastward
but the best chance will be during the morning across the eastern
county warning area.  Temperatures will be around 80 or in the lower 80s today with 850mb
temperatures around 14c and a fair amount of mid and high cloud cover.
Expect moSt Louisy mid 80s Saturday with slightly warmer mid level air
and probably more sunshine in the afternoon.

Things dry out for Sunday as upper ridging amplifies and shifts
eastward across the High Plains.  Surface high pressure will continue
with northwesterly flow aloft.  Waves will move through the flow but
be focused to the north and west across Minnesota and Wisconsin
Sunday into Monday.  Surface low pressure does take shape across the
northern High Plains late in the weekend then move northeastward
across Ontario Monday in conjunction with an upper low.  This will
flatten the flow and allow a surface front to drop towards the area into
Tuesday.  A gradual but steady warming trend is expected with most
areas near 90 by Tuesday.

Mdb

&&

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