Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 240034

Area Forecast Discussion
National Weather Service Quad Cities IA IL
734 PM CDT SAT JUL 23 2016

Issued at 734 PM CDT Sat Jul 23 2016

Area of thunderstorms beginning to diminish somewhat with only a
small cluster of strong storms just north of the Quad Cities and
into extreme nw IL. It appears the strong cap has suppressed
convection south of Interstate 80. Will be able to reduce pops as
the remaining storms move across.

Low confidence in convection overnight as the HRRR indicates
another line of thunderstorms sweeping northwest to southeast across
the cwa after midnight. However, it also progged a bunch of
convection in eastern SD but as of this writing only a lone storm
was near Watertown SD. Time will tell.

Regarding the heat headline: have let the excessive heat warning
expire even though a few locations south of Interstate 80 may
still experience 100 to 105 early this evening. Depending on
convective and cloud trends on Sunday another heat headline may be
needed south of Interstate 80 ahead of the cold front. Will pass
concerns on to later shifts.


Issued at 400 PM CDT Sat Jul 23 2016

SBCAPE of 6000 J/KG over southeast IA with the CAPE gradient
across our northern cwa. Deep layer shear and mid level lapse
rates were increasing in our north so line of thunderstorms, some
severe should move across our north late this afternoon into the
early evening. 3 pm temperatures ranged from the upper 70s at
Dubuque to the lower 90s at most locations. Dewpoints were in the
mid 70s to lower 70s, with heat index values ranging from 100 to 115.


.SHORT TERM...(This Evening through Sunday)
ISSUED AT 400 PM CDT Sat Jul 23 2016

Late afternoon through Tonight: HRRR takes a line of severe
thunderstorms eastward across roughly our northern half of the
cwa (I-80 northward) through early this evening. Due to the
extreme instability damaging winds 70+ mph and an isolated
tornado or two is possible with a boundary located in our far
north. Flash flooding is also possible in our northern cwa.

Low confidence in the overnight convection as most of the models
keep the MCS to the north of the cwa, but the HRRR brings remnants
of an MCS into our cwa. Will keep chance pops going through the
night. Lows will be in the mid to upper 70s.

Will let the heat warning expire at 7 pm even though a few
locations may still have heat index values of around 100 until
about 8 pm.

Sunday: Cold front will gradually work it`s way southeast across
the cwa, with continued chances for thunderstorms ahead of the
front. Later in the afternoon dewpoints will begin to lower.
In our southern cwa heat index values may rise to 100 to 105
so a heat advisory may be needed. However, this depends on any
cloud cover. Highs will range from the mid 80s to lower 90s.

.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 400 PM CDT Sat Jul 23 2016

Fair weather early this week then unsettled weather mid to late

Sunday night...Short deterministic models show high pressure will
build across the forecast area ending the oppressive heat wave as the
cold front that will produce thunderstorms on Sunday moves to the
south and east. The upper level flow aloft will be changing to the
northwest bringing slightly cooler and drier weather for early next
week. Low temperatures Sunday night will be in the mid 60s across
the north and around 70 across the south.

Monday and Tuesday...High pressure will be the dominate weather
feature with sunny skies and near normal July temperatures.
Dewpoint temperatures will drop into the mid to upper 60s making
humidity values more comfortable than the upper 70s and lower 80s
experienced during the recent heat wave. High temperatures both days
will be in the mid 80s with overnight lows in the upper 60s to near
70 Monday night and mid 60s Tuesday night.

Wednesday and Thursday...Mid range models prog a shortwave to move
across the Upper Mississippi Valley Wednesday into Thursday bringing
with it the possibility of more thunderstorms. This shortwave could
move to the south and east Thursday evening which may provide a very
brief dry period before the next short wave approaches Friday.

Friday and Saturday...Confidence is low in the timing of storms for
this time period with large discrepancies in long term model
solutions. The prudent thing to do at this point is to mention that
thunderstorms are possible Friday afternoon and Saturday as the next
shortwave approaches the region.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 734 PM CDT Sat Jul 23 2016

VFR conds expected through the taf cycle. Low confidence in
convective trends so for now will keep the tafs dry. A cold front
will arrive on Sunday with winds becoming northwest behind the
front. Ahead of the front winds will be from the south to
southwest around 10 knots or less.


.DVN Watches/Warnings/Advisories...


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