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fxus63 kdvn 280806 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
306 am CDT Mon may 28 2018

Synopsis...
issued at 304 am CDT Mon may 28 2018

Once again, our entire area remains under an upper ridge of high
pressure, and in the axis of impressive heat, and moderate humidity
early this morning. This same set up in the past two days has
brought heat index readings to near 100, and isolated strong to
severe thunderstorms in the afternoon hours where convergence has
occurred. That convergence has helped pool local dewpoints into the
mid 70s, and with that we aggressively reached convective
temperatures and exploded isolated thunderstorms. With a few
different nuisances, that is again possible today.

&&

Short term...(today and tonight)
issued at 304 am CDT Mon may 28 2018

The weak flow aloft and position of the upper ridge is allowing
convection to build southward through northern Wisconsin early this
morning. The convective allowing models (high-res cams), are on this
trend, and show an outflow moving southward through the morning
hours today near Lake Michigan, which should then spread easterly
flow over our northern County Warning Area this morning. That outflow boundary
position seems the likely spot for today's round of strong
afternoon convection. I will again paint in slight chances for the
zone, which for now is areas along and south of I-80, were storms
could develop. All of that convection will have to wait until we
reach the lower to mid 90s again, and therefore will not greatly
impact high temperature forecasts today. Highs today, much like
yesterday should be in the mid 90s in most location, with a few
upper 90s possible. Any storm that develops will have a high cape,
low shear profile, with high cloud bases (inverted v soundings),
supporting wet microburst threats and a some marginally severe hail.
Thus, will advertise a similar thunderstorms threat in the severe weather potential statement and
products today.

While not indicated directly, I am concerned that if the outflow
boundary arrives a few hours later in the morning, we may already be
near convective temperature. If that's the case, we could see
strong to severe storms moving southwestward through the County Warning Area during
the late morning. That's not likely, but it seems possible. So,
keep an eye on that boundary and it's timing!

The heat, yup, that's still a big story too! We've had 2 straight
days of near 100 heat index, and today appears to be a 3rd. I can
see some potential for a headline, but with the stronger winds today
than yesterday, it may feel quite a bit better out there. In any
case, it's near advisory level heat-(which is in excess of 100 heat
index widespread). Temperatures will certainly be near to above
records for this date. Please see the climate section below for
the record values.

Tonight, any convection will wane by sunset, and set up another warm
night, with cirrus clouds coming from distant thunderstorms.

Long term...(tuesday through sunday)
issued at 304 am CDT Mon may 28 2018

Main forecast concern in the long term are chances for precipitation
and temperatures. Tuesday looks to be a repeat of this weekend
before a 500 mb wave approaches the area from the west and Alberto
approaches the area from the south. After Tuesday, forecast skill
drops dramatically as an extratropical Alberto transitions into the
flow. Guidance begins rapidly diverging in the track of this
system. Differences in the track will lead to differences in
sensible weather. This discussion will focus on the Tuesday into
Wednesday then the two different model camps after Wednesday and
their respective sensible weather forecasts.

Tuesday into wednesday: Tuesday will begin 500 mb ridging in place with
with weak surface convergence across the area. Temperatures once
again will climb into the 90s. As the short term mentions, pooling
moisture along this axis will serve as the focus for afternoon
thunderstorm development. The difference between Tuesday and
today's environment is the presence of a eastward moving midlevel
wave. This wave should aid in thunderstorm development especially
along this axis Tuesday afternoon and evening. As Alberto moves
north, easterly flow will turn this convergent axis into a surface
front. Wherever this axis is in the afternoon, will be the primary
area to watch for storms. Shear is non-existent so cold pool driven
convection will dominate. Current synoptic models are not big on
this scenario, however the cams do suggest an active boundary. Into
Wednesday morning, models suggest convection continues overnight
along this axis. This seems reasonable as Alberto will continue to
bring moisture to reinforce convergence along the boundary.
Wednesday will be the best chance for convection and rain as Alberto
is prog across central Illinois and the best influence of the 500 mb wave will
affect the area. In fact overnight into Thursday am, deep layer
shear will be supportive of organized convection. Current rainfall
forecast could be too low. With all that said, if Alberto wobbles
further east, this discussion would be moot and chances for precip
would be lower and tied better to the 500 mb wave.

Into the weekend, one model Camp suggests that Alberto is ingested
into the largescale pattern and whisked away to the east. Another
Camp suggests that Alberto becomes cut off from the flow and spins
across the eastern US. If Alberto is whisked away in the flow then
500 mb ridging would favor a warm end to the week before a substantial
500 mb wave approaches later in period. We would continue to see Summer
across the area in this solution. The other scenario with Alberto
stalling across the eastern US would lead to easterly flow across
the area. This would likely bring cooler and drier air from the
Great Lakes. If the GFS is correct, we could see highs in the 70s
and even upper 60s this weekend, much more seasonable. Overall
confidence is low in this solution

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 1152 PM CDT sun may 27 2018

Weak high pressure will provide light and variable winds tonight
through Monday. There is a very low potential for ground fog
around sunrise, otherwise conditions will remain VFR. Isolated
thunderstorms are also possible in the afternoon and evening but
the potential for impacting the taf sites appears low at this
time.



&&

Climate...
issued at 304 am CDT Mon may 28 2018

Record highs for may 28...

Moline.........95 in 2006
Cedar Rapids...95 in 1991
Dubuque........93 in 1874
Burlington.....94 in 2006

Record highs for may 29...

Moline.........99 in 1934
Cedar Rapids...99 in 1934
Dubuque........97 in 1934
Burlington.....98 in 1934



Week 2...

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

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