Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 110808
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
308 AM CDT Fri Aug 11 2017

.SYNOPSIS...
Issued at 308 AM CDT Fri Aug 11 2017

Early this morning, surface low pressure slide east of Door County
Wisconsin into the northern mitten of Michigan. A cold front
associated with this low was slowly sagged across the CWA.
Northerly flow over Lake Superior led to the development of low
stratus that was filtering south towards the area. To the west, a
quick moving wave led to light showers across southern Iowa. This
wave and high pressure moving into the area will serve as the main
foci for the short term forecast.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 308 AM CDT Fri Aug 11 2017

Main forecast concerns for the short term are temperatures and the
potential for stratus this morning. Perfect fetch off of Lake
Superior led to the development of stratus and even some drizzle
across Wisconsin this morning. Current layer wind forecast is for
this stratus deck to move south into the area and then turn to the
east towards Chicago. RAP suggests that the best chance for
stratus is north and east of a line from Independence IA, to
Princeton, IL. The WRF simulated satellite data suggests and more
southerly flow of the stratus. Currently, the WRF seems to be over
aggressive. Will go with a consshort for sky conditions. Guidance
holds onto the cloud deck through noon today. This may be a little
to late, however at this time I have low confidence for timing of
break up so will go with guidance.

This cloud cover will then affect high temps for today. The high
temps are predicated on stratus holding on across the area
depicted in the RAP. If this does not occur, temps will need to be
raised. Regardless, it will be a nice low humidity day for mid
August.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 308 AM CDT Fri Aug 11 2017

Beautiful weekend weather will be found over the region as high
pressure remains in place for Saturday and Sunday. While warm
advection will result in a slight chance for showers and storms by
Sunday night, the remainder of the weekend will see a low humidity
air mass, temperate highs in the 70s to lower 80s, and plenty of
sunshine.

Looking toward Sunday night and Monday, an upper low will weaken
into an open wave aloft in the plains Sunday afternoon, and this is
the forcing for what could bring a few showers and storms to eastern
Iowa. This will likely not be a significant rain event for anyone in
our area as the storms are weakly forced and will be acting on a
seasonally dry air mass. In any case, another pleasantly cool high
pressure will be moving in for Monday and Tuesday, with the moisture
shunted well south and west during that period.

The GFS and EC both show a convectively active warm front working
northeast over our region Wednesday and Thursday, with diffuse
forcing in a transition to northwest flow Friday.  This results in
our forecast showing pops on several days, along with building heat.
If heat does build in as forecast, it will be short lived before the
transition to northwest flow. The EC is quick in this transition,
while the GFS shows a slower, more convectively active transition
with a heavy rainfall event for Friday. There is certainly time to
determine this day 6-8 rain potential with more refinement in the
coming days.

ERVIN
&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1137 PM CDT Thu Aug 10 2017

Fast moving upper level wave will bring sprinkles and spotty
light showers to areas south of I-80 prior to daybreak, and have
handled with vcsh wording at BRL but left out at MLI. Otherwise,
front nearing Mississippi River will gradually shift southeast
of the terminals by sunrise with N/NW winds 4-8 kts. Some patchy
fog is possible overnight through daybreak, but enough uncertainty
given unfavorable northerly wind even being light precludes from
mention. Late tonight and Friday morning anticipate stratus with
areas of low VFR to MVFR cigs to develop at all sites, except for
BRL. There is a low probability of IFR cigs at DBQ Friday morning.
High August sun angle and drying on increasing NW winds around
10 kts during Friday should bring about a gradual lifting of cigs
to VFR toward midday into the afternoon, with clearing by evening.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Ervin
AVIATION...McClure



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