Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 210247

Area Forecast Discussion
National Weather Service Quad Cities IA IL
947 PM CDT Tue Jun 20 2017

Issued at 947 PM CDT Tue Jun 20 2017

Strong 850 mb moisture return in the plains was evident from 850
mb analysis and various IR and WV loops advancing north-northeast
across Nebraska. This process is expected to advance into
central and northwest IA toward morning, where it has at least a
low potential for producing scattered showers and thunderstorms
that may reach into eastern IA. This has been advertised by some
convective allowing models, which indicate a potential for at
least scattered showers and thunderstorms continuing through the
day across the north as the surface warm front retreats northward.

Have updated the forecast to bring in slight to low end chance
pops for thunderstorms during the day and tweak temperatures
downward slightly over especially the north, where this scenario
would lead to more cloud cover.


Issued at 330 PM CDT Tue Jun 20 2017

Impressive temperature gradient across the northeast CWA this
afternoon and temperatures in the 60s exist in south central
Wisconsin and temperatures in the mid 80s across eastern IA. Water
vapor depicts a short wave moving through central Wisconsin.
Convergence along this boundary in association with an upper level
wave will lead to showers and thunderstorms the rest of today and
through the beginning of the short term period.


.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 330 PM CDT Tue Jun 20 2017

Main forecast concern for the short term will be how long convection
continues through sunset and then whether or not we will see much
late in the period as the front becomes active again to our north.
This afternoon a backdoor cold front is moving into the area.
Convergence along this system will lead to showers and
thunderstorms.  Isolated severe storms with hail and damaging wind
will be possible this evening.  With the loss of daytime heating,
think convection will quickly end after this point.  Tonight
temperatures should drop into 50s across the area.

Tomorrow, current guidance keeps precip out of the area until near
00z.  Think that the placement of tomorrows boundary is too far
north and will likely be closer to our area.

.LONG TERM...(Wednesday Night through next Tuesday)
ISSUED AT 330 PM CDT Tue Jun 20 2017

Wednesday night...Will have to watch out for what lingers out of
the Wed afternoon elevated shower and possible storm activity
drifting east acrs the northern third to half of the DVN CWA wed
evening. But then the prime thunderstorm regeneration may then
refocus back to the northwest acrs northwestern IA into southwestern-
south central MN Wed evening. Currently progged propagation vectors
and mean westerly mid layer steering flow itself, would allow an
evolving storm cluster or even a type of MCS to move east-southeast
and impact portions of the DVN CWA after midnight into thu morning,
especially the northern half again. Bulk of the latest run solutions
propagate the more significant late night storm clusters along and
north of the CWA into Thu morning, but can`t totally trust that
scenario and could easily see a more southward propagation. If the
storms make it down acrs our area, still a threat for marginally
gusty winds and heavy rain even at a late night occurrence. Low temps
by early Thu morning in the mid 60s where rain cooled outflow
occurs, to around 70 in the milder locations.

Thursday and Friday...Thu and especially Thu night, could be a
stormy period typical of late June. Much will depend on what occurs
Wed night and lingers into Thu, convective debris-wise and boundary
placement. A type of model ensemble of several solutions, suggest a
lingering west-to-east outflow boundary from Wed night, combined
with a main ENE-to-WSW oriented cool front sagging into the northern
CWA, may be a focus for later afternoon and evening convective
development in or close to the local fcst area. This boundary will
be interacting with an increasingly unstable, warm-moist airmass
along and south of it. High temps in the upper 80s to around 90, and
sfc DPTs climbing at least into the upper 60s will make for late
afternoon CAPES of over 3000 J/KG. Bulk shear profiles increase to
40-55+ KTS into Thu evening as a short wave propagates east toward
the area and in VCNTY of the boundary/boundaries. With the boundary
in mind, see all modes of severe weather possible with any individual
cells that develop overhead or evolving storm complex that moves in
or also develops locally. Most solutions erupt early evening
convection from west-to-east acrs much of northern third of IA, and
then a resultant MCS propagates south and southeast during the
evening and overnight, feeding on the high CAPEs and producing gusty-
damaging winds with evolving bow segments.  But again, can`t rule
out storms developing/initiating further south acrs the north half
of the DVN CWA Thu evening if that`s where the main boundary lays
out...further south than what most models give it credit for.

Besides the severe storms threat THe evening and night, a projected
PWAT feed of 1.8 to 2+ inches suggest heavy rain and possible flash
flooding also a concern into early Fri morning. Extent of shear and
column saturation supports a few swaths of 2 to near 3 inch rainfall
amounts possible by Fri morning.

After any lingering rain exits to the south Fri morning, expect the
rest of the day to be a dry, breezy and cooler post-frontal day with
highs in the upper 70s to low 80s.

Saturday and Sunday...Digging northwestern flow and L/W upper trof
establishment acrs the Upper MS RVR Valley and into the GRT LKS,
should make for a much cooler weekend ahead. Highs to be held well
below normal only in the 70s to around 80, and overnight lows well
down in the 50s. Some 40s even possible especially Sunday night. an
embedded clipper-like wave may generate sctrd showers and
thunderstorms late Sat and Sat night, but low confidence on timing
and instability that this system will be able to utilize.

Next Monday and Tuesday...Northwest upper flow and cooler than normal
regime will look to continue into early next week, before return flow
moderation tries to build back acrs the region late Tue or next Wed.
Elevated precip events possible with any organized warm push back
over cooler retreating air.    ..12..


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
ISSUED AT 625 PM CDT Tue Jun 20 2017

VFR conditions are expected tonight through Wednesday. Scattered
afternoon thunderstorms have moved south of the region early
this evening ahead of a cold front that will lead to clear skies
and light northeast winds overnight. Wednesday, there is a very
low potential for afternoon thunderstorms, especially at CID and
DBQ, which are not included in the forecasts.




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