Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 230807

Area Forecast Discussion
National Weather Service Quad Cities IA IL
307 AM CDT Wed May 23 2018

Issued at 255 AM CDT Wed May 23 2018

High pressure was centered over WI and northern IL early this AM.
Light winds and mainly clear skies has allowed temps in these
areas to drop into the lower to middle 50s, and also resulted in
the formation of some fog. Further west temperatures were being
held up in the 60s due to cloud cover and light east/southeast
winds. Elevated arcing band of storms extends from southwest MN
through north central IA early this morning. Convection was
occurring within zone of strong theta-e advection and 850 mb
convergence/ confluence downwind of mid level instability axis.
Meso-Beta Elements (MBEs) moving southeast at a right angle to
inflow creating a favorable setup for repeated activity and
locally heavy rain. With MBE vectors from northwest, and low level
jet (LLJ) veering but weakening we will have the potential to see
some propagation and/or development of convection into eastern IA
until mid morning before nocturnal LLJ and attendant kinematic
processes wane.


.SHORT TERM...(Today and Tonight)
ISSUED AT 255 AM CDT Wed May 23 2018

Will have mention of fog along and especially east of the Mississippi
River through daybreak. Fog could be patchy dense in portions of
northern IL. Otherwise, watching the convection over north central
IA. Will have low to moderate PoPs until mid morning for portions
of eastern IA (mainly along/n of I-80) to account for possibility
of scattered elevated showers and even a few storms drifting and/or
developing into some areas west of the Mississippi River before
LLJ wanes. Lightning and locally heavy downpours are the main threats
from any storms. For the afternoon expecting partly to mostly sunny
skies. Humid conditions are on tap west of the Mississippi River
within low level moist axis characterized by dew points in the 60s.
Slightly drier air with dew points in the 50s expected into northern IL
being in close proximity to departing high. Highs should top out in the
upper 70s to middle 80s. Can`t completely rule out a shower or weak
storm late this afternoon across the far south with convective
temps breached, but lack of any other apparent trigger lends support
for too low of coverage for mention... should it even occur.

Tonight, mainly clear to partly cloudy. Elevated weak theta-e advection
may lend to some accas and low potential of a shower west of the
Mississippi River, but again in absence of other trigger any coverage
would appear too isolated for mention. Lows coolest east (mid/upper 50s)
and warmest south/west (mid 60s).

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 255 AM CDT Wed May 23 2018

Long term period will be dominated by weak upper level flow as large
stationary trough is forecast to remain across the SW CONUS.
Overall, ridging to weak SW flow will drive the weeks weather. This
will lead to a warming and increasing moisture trend through the week.
Numerous waves will pass through the flow leading to chances for
showers and thunderstorms with each wave. Overall chances for strong
to severe storms will be tied to mesoscale features that will not be
resolved until the day of the storms.

First wave is expected to move into the area Wednesday into Thursday
morning.  Overall shear is weak with this system, suggesting that
organized updrafts will be difficult.  The question now turns to
rain.  PWs will be high, above 1.5 inches, however there appears to
be a lack in H85 flow that will lead to the needed moisture
transport.  Much like the past few days, isolated heavy rain is
possible, but not widespread.  This environment will remain in place
until the end of the week, when better chances for showers and
thunderstorms will return to the area.  From a sensible weather
point of view, it will feel a lot more like summer.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1216 AM CDT Wed May 23 2018

VFR conditions expected to largely dominate the TAF cycle. Light
winds and moisture will result in some patchy fog with
visibilities 2-5sm after 23/10z to 23/14z. Also, watching an area
of showers and storms over north central IA attendant to elevated
warm, moist advection. Some of this activity may drift and/or
develop into eastern IA toward 12z through mid morning before
diminishing. KCID would appear to have best chances for seeing
some of this activity, but spotty coverage limits mention to just
VCSH for now. Any shower and storms will have potential for MVFR




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