Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 241202
Area Forecast Discussion
National Weather Service Lincoln IL
702 AM CDT Thu Jul 24 2014
ISSUED 248 AM CDT Thu Jul 24 2014
Drier air has spread over the entire forecast area, with dew
points at 2 am as low as 49 degrees at Effingham. Large high
pressure across northern Minnesota is building southward,
resulting in mostly clear skies across the area early this
morning. Upstairs, high pressure ridging continues from New Mexico
to North Dakota, with a strong 500 mb low over Washington state.
This low will be more of a player for our weather later in the
weekend. In the meantime, trying to time the extent of nocturnal
convection will be the main forecast concern for this package.
SHORT TERM...Today through Saturday Night:
Quiet weather expected through this evening, as the high pressure
settles into the Midwest. Mid to upper 70s likely for highs today,
as dew points remain quite comfortable (50s) for late July.
Upper ridge expected to break down this evening as the low tracks
across the southern parts of British Columbia and Alberta. This
will allow a surface low over Montana to dive southeast into
eastern South Dakota overnight. Strong low-level jet of 45-55
knots along the 850 mb warm front expected to result in an MCS
forming toward midnight across Iowa, before tracking southeast.
Rather pronounced dry wedge around 800-850 mb is shown on NAM and
GFS forecast soundings tonight, and the general model suite
continues to slow the arrival in our area as a result. Thus, have
kept just slight chance PoP`s northwest of the Illinois River late
tonight, and concentrated the main chances of rain across the
north half of the CWA during the day on Friday. Convection should
be fairly elevated, limiting the severe threat. Development of
another MCS is expected Friday night across Wisconsin and northern
Illinois, with elevated convection moving through the forecast
area late night and early Saturday. The remainder of Saturday will
likely remain capped, before yet another MCS forms late afternoon
or early evening. This last MCS is the one most likely to produce
severe weather, with very unstable CAPE`s over 3000 J/kg and 0-6
km shear becoming more decent around 35-40 knots. Latest SPC Day3
outlook does include the entire forecast area in 15% probabilities
(slight risk) of severe weather for Saturday afternoon/night.
LONG TERM...Sunday through Wednesday:
By early Sunday, the earlier mentioned upper low will be opening
up some as it drops southeast into northeast Minnesota. Some
lingering convection is possible on Sunday, before the passage of
a cold front ahead of this wave. Have kept the remainder of the
forecast dry, as high pressure builds into the mid Mississippi
A broad upper trough will dominate the Midwest most of next week,
as an upper low spins over southern Hudson Bay. This will result
in another shot of cooler weather early next week, with some
slow modification in temperatures. However, below normal
temperatures will prevail beginning on Monday. Long range
indications are that this below normal trend will continue into
the first few days of August.
ISSUED 700 AM CDT Thu Jul 24 2014
High pressure and dry air today will help keep VFR conditions for
all terminal sites over the next 24 hours.
An early look at the 12z KILX sounding shows 25kts of wind from
050 at 600ft AGL. We could see some gusty northeast winds at
times this morning after mixing develops.
Winds should weak with diurnal cooling this evening. Clouds will
be minimal today, with just a few cumulus in the 4-5k level.
Storms could approach PIA late tonight, but we only included
increase mid clouds after 10z tonight for now.
DEC ob site is still down, so amendments are not scheduled at
night, when the airport tower does not augment observations.