Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 171612
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1112 AM CDT Sat Jun 17 2017

.UPDATE...
Issued at 1053 AM CDT Sat Jun 17 2017

Forecast has been adjusted a bit to account for a southerly shift
in potential for severe storms this afternoon.

There still remains the question as to how much activity will be
seen across the entire CWA as the focus for storms will be over
the southeast portion of the area.

The cold front is still looking to move into the western part of
the forecast area near mid to late afternoon and quickly shift
southeast. Mesoanalysis reveals a boundary in place across the
forecast area, roughly from KOTM to KCWI. Areas north of this line
will have a lesser potential for significant storms today and the
outlook has been scaled back. Looking to the south of this
boundary, the low level enhanced flows look to be focused further
south than previous forecasts were anticipating. Still believe
there will be convection firing along and south of the boundary
as it moves southeast later this afternoon, but coverage may be
more scattered, rather than widespread. CAMs are picking up on
this southern shift and have widespread convection along the front
around 03Z this evening, which will primarily be south of the
local forecast area. Any timing shift though could change this
scenario so it will continue to be monitored closely through the
afternoon.


&&

.SYNOPSIS...
Issued at 350 AM CDT Sat Jun 17 2017

MCS that moved into our nw cwa last evening stratified out during
the night and basically has been a beneficial heavy rain maker
instead of a severe weather event.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 350 AM CDT Sat Jun 17 2017

Forecast focus on potential for significant severe weather event
and SPC has an enhanced/slight risk over the cwa.

Current MCS should exit the cwa early this morning followed by a
decrease in clouds which should allow temperatures to rebound well
into the 80s this afternoon. I do not see a trigger for
additional storms for most of the day, as we will be somewhat
capped. However, by late this afternoon strong to severe storms
should rapidly develop. This is when a deepening upper level
trough, increasing shear as 70-80 knot mid level winds, and
rather strong cold front arrives to provide the forcing needed to
trigger the thunderstorms.

The thinking hasn`t changed in regard to modes of severe weather
(damaging winds of 70-80+ mph, large hail and potential for an
isolated tornado or two). At some point this evening an
organization of the storms into a fast moving linear line should
occur with an enhanced risk of very damaging winds. However,
confidence has lowered since yesterday of the exact locations in
the cwa where the severe storms will form. The ECMWF basically
keeps our north half dry whereas most other models indicate storms
firing over most of the cwa. The day shift will need to monitor
trends but for now will keep likely pops over most of the cwa. The
storms should move out of the cwa by midnight or shortly thereafter.

With temperatures rising into the mid to upper 80s and dewpoints
in the lower to mid 70s, the heat index values will soar into the
mid to upper 90s. This will be especially true south of Interstate
80. However, this is below the headline criteria. Lows tonight
will be in the lower to mid 60s.

.LONG TERM...(Sunday through Friday)
ISSUED AT 350 AM CDT Sat Jun 17 2017

Forecast focus on below normal temperatures through early next
week then a return to warm and stormy pattern later in the week.

Sunday through Tuesday: Northwest flow providing pleasant mid June
weather with below normal temperatures and comfortable humidity.
Highs will be in the 70s to around 80 with lows in the 50s.

Wednesday through Friday: Zonal flow returns with a warm front
lifting into the cwa and then stalling. Periodic rounds of
thunderstorms are expected but low confidence in timing. This far
out it is too early to assess the severe weather potential. Highs
will be well into the 80s with lows well into the 60s to around 70.
Another strong cold front is expected to arrive by Saturday of
next weekend, returning below normal temperatures.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
ISSUED AT 659 AM CDT Sat Jun 17 2017

Mainly VFR conds through this taf cycle except MVFR/lcl IFR
cigs/vis in/near tstms late this afternoon and evening. Southwest
to south winds today becoming northeast with a passage of a cold
front this evening.


&&

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

$$

UPDATE...Brooks
SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Haase
AVIATION...Haase



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