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118
FXUS63 KDVN 191049
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
549 AM CDT Sun May 19 2019

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 325 AM CDT Sun May 19 2019

The better forcing on the nose of the LLJ has shifted northward
and much of the showers and storms were north and east of the dvn
cwa. A few showers and storms were noted in northern/central MO.
Temperatures across the dvn cwa early this morning were in the mid
60s at most locations.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 325 AM CDT Sun May 19 2019

Headlines: The flash flood watch has been cancelled as the threat
of widespread heavy rainfall has ended. The airmass was becoming
drier and shear/instability was minimal.

Today: A few showers and isolated thunderstorms can be expected
mainly this morning as low pressure tracks from eastern IA into
northern Lower MI later today. The airmass will continue to dry
out as winds turn southwest with decreasing coverage of showers.
The main area of stronger storms later today looks to be well
east of the dvn cwa along the cold front.

Forecast soundings indicate a deep sw to w flow in the column
with 35-40 kts winds at the mixed layer. This will be a windy day
especially from late this morning through the afternoon.
Considered a wind advisory but for now the situation looks
marginal for headlines, but the day shift can monitor trends. As
of now, wind gusts of around 40 mph seem likely. Highs will range
from the lower 60s nw to the lower 70s se.

Tonight: A quiet and believe it or not a dry night expected as
low pressure pushes into the northern Great Lakes region, and high
pressure ridge builds into western IA from the northern Plains.
Skies should clear after midnight and w to nw winds will gradually
diminish. Temperatures will be colder with lows in the upper 30s
to lower 40s.

.LONG TERM...(Monday through Saturday)
ISSUED AT 325 AM CDT Sun May 19 2019

Cool temperatures to start the week followed by a warm up and then
another cool down for next weekend. Overall weather pattern to
remain very active with several rounds of rain.

Monday
Assessment...high confidence

Dry and very cool conditions will be seen Monday as high pressure
quickly moves through the Midwest. Temperatures will average around
10 degrees below normal.

Monday night
Assessment...medium confidence

Mainly dry conditions will be seen across the area during the
evening hours as the next storm system approaches from the Plains.
Late Monday night rain will begin overspreading the area with the
better rain chances across the western third of the area. The model
consensus has slight chance to likely pops for late Monday night.

Tuesday and Tuesday night
Assessment...high confidence on rain occurring. Low confidence on
amounts and severe potential

The next storm system moves the main low north through the Plains.
Easterly flow over most of the area will keep cool temperatures for
much of the day. Temperatures may warm late in the afternoon south
of I-80 as winds turn more southeast.

The strongest forcing and thus better chances for rain are generally
across central Iowa. There is some good forcing occurring into
northeast Iowa which should help enhance rain potential west of the
Mississippi. The model consensus has chance to likely pops Tuesday
with likely pops Tuesday night.

The large scale shows the Gulf wide open and feeding deep moisture
into the Plains and Midwest. Thus the heavy rainfall risk is real.
Central Iowa is currently favored for heavy rainfall but rainfall
amounts of 1 to 2 inches are very possible across eastern Iowa. This
situation will have to be watched closely for possible headlines.

The initial cool temperatures means than rain will be seen during
the morning and early afternoon hours. As forcing increases with the
approach of the upper level part of the storm system, thunderstorms
should begin developing by mid to late afternoon and continue into
Tuesday night.

Regarding the severe potential; the shear in the atmosphere is
tremendous. However, the atmosphere only becomes marginally unstable
due to the cool temperatures. Thus while there is a severe risk the
window for any severe storms looks to be quite narrow and confined
to the late afternoon and early evening hours with hail being the
primary risk.

A wind risk `may` be possible if storms can organize into a line
across Missouri that races northeast into the area. The line
scenario is within the realm of possibilities given the more
unstable atmosphere across Missouri.

Wednesday on...

Wednesday
Assessment...high confidence

Quiet, dry and warmer conditions will be seen on Wednesday as high
pressure moves through the Midwest. Temperatures should average
above normal.

Wednesday night through Saturday
Assessment...low to medium confidence

The models diverge with their respective solutions. They do suggest
somewhat similar scenarios but differ on the details.

All four global models develop a boundary from northern Missouri
into central Indiana Wednesday night. The FV3 has it as a surface
boundary while the GFS, CMC global and ECMWF have it as an upper
level boundary.

Said boundary remains in place through Thursday before lifting north
of the area Thursday night/Friday. Another storm system then drags a
surface cold front through the area in the Friday through Saturday
night time frame.

While the overall scenario is similar between the global models
there are differences in the details regarding timing of rain and
potential rainfall amounts. The model consensus is somewhat biased
toward the GFS and CMC solutions.

Currently the model consensus has chance to likely pops Wednesday
night and Thursday, mainly dry conditions Thursday night (due to the
CMC global), and then slight chance to chance pops Friday through
Saturday. Areas south of highway 30 are favored Friday and Friday
night. For Saturday areas south of I-80 are favored.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
ISSUED AT 546 AM CDT Sun May 19 2019

Scattered showers and isolated thunderstorms will affect the TAF
sites this morning. VSbys will drop with any storm. CIGs
eventually lower to MVFR/lcl IFR today into this evening.
Southwest to west winds increase to 30 to 35 knots later this
morning through the afternoon.

&&

.HYDROLOGY...
Issued at 1225 PM CDT Sat May 18 2019

A line of thunderstorms that tracked through the area this morning
produced rainfall roughly in a .25 to .5 inch range with local
heavier totals, based on both radar and surface reports. The
relatively fast movement of the heavy rainfall rates has prevented
any short term hydro issues. A Flash Flood Watch is in effect for
tonight through mid morning Sunday in anticipation of the next round
of potentially heavy rainfall, that will occur with nearly saturated
soil conditions now in place.

Latest trends suggest a break in the rain is expected early this
afternoon, then another thunderstorm complex with heavy rainfall
currently over KS and OK will pass through the forecast area late
this afternoon into overnight. This will have the potential for
widespread heavy rain and the latest river forecasts have these two
events incorporated, with expected rainfall totals of around 1 inch
east to 2 inches in the far west, which is a conservative, middle
range of possibilities. As a result, new river forecasts this
morning, incorporating this rainfall, have much higher levels than
yesterday, on both tributary rivers and the Mississippi River, This
has resulted in higher levels, new flooding and higher category
flooding on area rivers, and numerous flood warnings went out this
morning, as detailed below.

On the tributary rivers: Rapid rises are expected over the next
couple days. Moderate flooding is now expected on the Wapsipinicon
at Dewitt. On the Skunk River, Sigourney is now forecast to reach
the upper levels of Moderate flooding and Augusta reaches Moderate
flooding as well. On the Iowa River, Marengo surges much higher into
Moderate flooding, while Wapello and Oakville are now forecast to
reach Minor flooding. On the Cedar River, only within bank rises are
expected. The English River at Kalona is now forecast to climb into
Moderate flooding. The Des Moines River is also forecast to rise
into Minor flooding. On the Illinois side, within bank rises are
expected at Freeport, while the Rock River will rise above flood
stage at Moline and stay longer above flood stage at Joslin. The La
Moine River at Colmar is forecast to climb sharply, but crest below
flood stage early next week.

On the Mississippi River: Forecasts have risen considerably, now
that this weekend system`s QPF (total rain forecast) is taken into
account. Warnings for Minor to Moderate flooding were issued this
morning for Dubuque LD11, Dubuque Railroad Bridge, Fulton, and Le
Claire. At Rock Island, a higher and prolonged crest into Moderate
flooding is now expected.  A change from Minor to Moderate flooding
was made for Muscatine and from Moderate to Major flooding issued
for Keithsburg and Gladstone. At Burlington, the new forecast has a
higher crest, now close to Major flooding occurring early next week.
Keokuk rose from Minor flooding to Major flooding, likely due to the
contribution of upstream tributaries. Gregory Landing stays within
Moderate flooding, but crests much higher than the previous forecast.

These forecasts will likely change some as rainfall amounts and
coverage are taken into account. Another system with potentially
heavy rainfall is expected Tuesday, which may result in additional
rises, renewed flooding or higher category flooding and is not
incorporated in the current river forecasts.

&&

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

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...08
AVIATION...Haase
HYDROLOGY...Sheets