Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 171955

Area Forecast Discussion
National Weather Service Quad Cities IA IL
255 PM CDT Sun Sep 17 2017

Issued at 254 PM CDT Sun Sep 17 2017

The surface cold front which moved through the area with dissipating
rains prior to dawn is now from near Chicago to Kansas City. With
dry air flowing in behind this front, there should be no rainfall
through the evening hours.  Very pleasant conditions are found over
the upper Midwest, with dewpoint in the 40s and 50s.


.SHORT TERM...(This Evening through Monday)
ISSUED AT 254 PM CDT Sun Sep 17 2017

A confidently dry evening will given way to questionable pops for
the rest of the night, as a short wave trof over Nebraska and Kansas
lifts northeast over the frontal boundary. Models move this main
short wave over Iowa into Wisconsin during the day Monday, while
keeping the front south. This puts most of our CWA into a position
where rainfall could once again appear robust as it enters the
western counties toward morning, but dies on arrival. Ad the main
short wave support lifts north, it will separate from the main CAPE
pool south of the front. Thus, I expect the rains to split around
the CWA, with better coverage lifting into Wisconsin, and stronger
intensities staying south in Missouri. The global models of the
GEM/ECMWF/GFS do not resolve this issue, but I am thinking the
depiction of that split seen in the 12Z NMM and ARW models is on
target, as it looks very similar to this past morning. Given, this
potential, I have limited the likely pops to the western areas in
the morning to northwest in the afternoon, while keeping the
southeast in lower chances.

In any case, the thin cloud cover and dry air should allow for low
in the upper 40s to lower 50s in the north half, and mid 50s south,
followed by widespread cloud arrival early Monday. The clouds and
east winds will hold temperatures down to the mid 60s northwest to
mid 70s southeast.  If the rain does come in more widespread than
this scenario, we could be a few degrees colder.


.LONG TERM...(Monday Night through Sunday)
ISSUED AT 254 PM CDT Sun Sep 17 2017

Forecast focus on a mainly dry and summer-like pattern for at least
the next 7 to 10 days, with expectations the drought will continue
to worsen across all of the dvn cwa.

Monday night: Short wave coming across the area will generate
scattered showers and a few thunderstorms. However, the forcing
looks to weaken so not looking for widespread or significant rain.

Tuesday through this weekend: Blocked pattern again with models
depicting a deep upper level trough in the western United States,
and ridging in the east. To add to the confidence of this blocked
pattern is the active Atlantic hurricane season, with "Jose", "Lee"
and "Maria" currently all lined up in a row. See the National
Hurricane Center`s website for more details. In fact, as the week
progresses high pressure aloft will strengthen in the Great
Lakes/Ohio Valley.

What this means for the dvn cwa is an extended period of very warm
temperatures with no rain expected, as the main synoptic
front/forcing will be out in the Plains. Highs will be well into the
80s, with some lower 90s likely each day. The consensus models may
not be warm enough. Also, low confidence in pops that the models
indicate in the grids. These very warm and dry conditions will
worsen the drought across the dvn cwa that began in mid to late July.



.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1218 PM CDT Sun Sep 17 2017

A cold front has swept through all TAF sites in eastern Iowa and
northwest Illinois as of 15Z today, and dry air is now filtering
in behind the front. The period of MVFR cigs are ending from north
to south already, and only BRL has been included in one more hour
after 18Z of these cigs. Northwest winds will become light
northeast tonight, under high overcast to clear conditions.
Towards morning, an area of rain, possibly with thunder will move
east towards the area. The is highly questionable with respect to
intensity, and since there is little low level moisture, this
seems to have little risk for low cigs until rain is well
developed. The timing of rain seems move probably after 18Z




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