Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 070524
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1224 AM CDT Tue Apr 7 2020

...06Z AVIATION UPDATE...

.UPDATE...
Issued at 919 PM CDT Mon Apr 6 2020

Storm development appears low tonight across our cwa per capping
inversion(s) noted on 00z DVN raob, and lack of stronger trigger
or forcing mechanism noted in UA data. The focus for the low
storm chance however would be across portions of our N IL
counties where low level jet and theta-e advection is focused.

Otherwise, still seeing some signal for dense fog potential
overnight mainly near the Hwy 20 corridor north of the warm front.

Tuesday harbors a conditional PM severe storm risk. Uncertainty
exists as to whether the cap or layer of warm air aloft will
be broken along a cold front. Some of the early data for tomorrow
shows low level convergence may be weak with not much forcing
aloft. But, we have a great chance to make a run at 80 degrees for
highs tomorrow, which would greatly weaken this cap. Should this
occur plenty of deep layer shear and dry air for attendant large
hail and damaging wind risk, but again a risk conditional upon
storms being able to initiate. Have updated the hazardous weather
outlook to include this mention.

&&

.SYNOPSIS...
Issued at 330 PM CDT Mon Apr 6 2020

The latest regional RADAR loop was indicating isolated to widely
sctrd elevated showers moving east along and north of H9 MB warm
front draped from west to east generally acrs central IA over to the
MI/IN border region. Some lightning detected earlier, but much of
that has fallen out/decreased lately. The current water vapor loop
was indicating a few upper ridge-riding vorts acrs eastern CO and
NE, with them looking to propagate eastward acrs IA and toward the
southwestern GRT LKS through Tue morning.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 330 PM CDT Mon Apr 6 2020

Tonight...Convergent 35-40 KT elevated southwest flow will still
look to fester sctrd showers and some thunderstorms based above H85
MB this evening and overnight. Plume of 500-1000 J/kg low to mid
layer MUCAPEs with some storm layer shear of 25-35 KTs projected to
sweep acrs the CWA this evening supporting thunder and pea size hail
potential with the more enhanced cells, as well as mid layer lapse
rates of 6.5 to near 7 C/km. But both the 12z run NAM80 and UKMET
MCS tools that we have a continuing lobe of precip making-support
mainly along and north of I80 this evening for more uptick in
activity, but the prime support for more robust storms looks to take
place off to the east along the eastern IL/WI border region,
southeastward into northern IN later tonight. With a precipital
water feed of an inch plus and shear profiles, this is where the
more robust storms with hail potential and locally heavy rain swaths
should fall out. This while the entire DVN CWA may have more sctrd to
isolated lighter activity much of the night. But will still have to
be on the watch for a band of heavier thunderstorms that may develop
further west along the I80 corridor east of the Quad Cities later
tonight around midnight or so. Hail and locally heavy rainfall would
be the main concern with these storms from Henry IL to Bureau
Counties. Unless a more developed band of storms can back their way
westward and make it into eastern portions of the fcst area, most of
the area to receive general widespread rainfall amounts of a quarter
inch or less through 12z Tue morning. 12 hour low temps held up in
the upper 40s to mid 50s tonight as the warm front(or fronts) try to
retreat northward.

North of the LLVL warm push, patchy to areas of fog may form along
and north of the Hwy 30 corridor by as early as mid evening. Some
fog may go dense and can`t rule out the need of an advisory,
before increasing south winds and mixing can push the fog to the
north by Tue morning.

Tuesday...As the prime digging short wave trof and sfc reflection
low pressure/frontal system sweep east acrs MN and WI, much of the
CWA should be bathed in this sytem`s warm sector. Depending on cloud
cover and mixing into base of inversion/warm cap aloft, temps will
stride well up in the 70s tomorrow. This combined with sfc DPTs in
the upper 50s to low 60s will make for SBCAPEs of 1000-2000 J/KG.
But fcst soundings suggest the elevated mixed layer stout and may be
hard to break with convective temps of upper 70s to mid 80s on the
fcst soundings. Thus besides a rogue elevated shower, the CWA may
remain largely dry through late afternoon. But if the cold front
that will move acrs the northwestern third to half of the CWA can
scoop up parcels enough to break the CAP, strong to severe storms
with all modes of threats may be possible in the northern to eastern
CWA by late afternoon. Will advertise low to medium chance POPs for
this potentail, but hope the CAP will hold and shunting better
convective initiation to the east and southeast of the DVN CWA by
Tue evening.  ..12..

.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 330 PM CDT Mon Apr 6 2020

Overview: Model forecasts predict a mean ridge over the northeast
Pacific, with positive 500-hPa height anomalies along the West
Coast. Downstream, an amplified mean trough centered over the upper
Midwest and Great Lakes favors negative 500-hPa height anomalies for
much of the country from the Rockies to the East Coast.

Enhanced probabilities for below-normal temperatures are favored for
much of the central and eastern United States, in association with
an amplified mean trough. Large probabilities (80 to 90 percent, or
more) of below normal temperatures across the Great Plains and
Midwest are supported by good model consistency with the high
amplitude pattern along with daily negative departures from normal
of more than 15 degrees below normal for mid April. Precipitation is
expected to be about normal.

Details:

Wednesday into Wednesday night: Upper level trough bringing forcing
to the area along with a strong cold front should spread an area of
showers and a few thunderstorms. The rain should end in our eastern
cwa during the evening. Rain amounts look to be less than one-half
inch at most locations.  ECMWF/GFS suggest the better forcing is in
our north half so will have likely pops there, with plenty of room
to increase these pops.  Enjoy the warm temperatures with highs in
the 60s to lower 70s, as a major pattern change to much colder
weather begins after this time frame.

Thursday through Monday: The main message will be much colder
temperatures with highs in the 40s and 50s with lows in the 30s.
Low confidence in precipitation.

Haase

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
ISSUED AT 1224 AM CDT Tue Apr 7 2020

IFR conditions due to low clouds and fog at DBQ will likely
improve to MVFR late tonight as a warm front lifts north through
the region. Scattered showers along this boundary will likely also
impact the DBQ site until around 07Z. Elsewhere, VFR conditions
should prevail at CID, MLI and BRL through the night. During the
day Tuesday, winds will become gusty from the southwest with
continued VFR conditions. A cold front may bring isolated showers
and thunderstorms, which are mentioned in PROB30 groups at CID,
DBQ and MLI for late afternoon into early evening.

&&

.HYDROLOGY...
Issued at 1230 PM CDT Mon Apr 6 2020

On the Mississippi River: Minor to moderate flooding to continue
this week with most locations still seeing rises. However, the
crest is forecast to reach Dubuque to Bellevue between April 7 and
April 9, with the crest working farther downstream (Fulton to
Gregory Landing) during the April 9 to April 12 time frame.

On the Rock River at Joslin: The river continued to fall and is
forecast to go below flood stage early Tuesday morning.

Precipitation: The pattern does become more active around the
middle of April bringing the potential for rain or snow. However,
too early to tell if this will impact any rivers.

Temperatures: Below to well below normal through the next 2 weeks,
and possibly beyond.

&&

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

$$

UPDATE...McClure
SYNOPSIS...12
SHORT TERM...12
LONG TERM...Haase
AVIATION...Sheets
HYDROLOGY...Haase


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