Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 202354

Area Forecast Discussion
National Weather Service Quad Cities IA IL
654 PM CDT Sun May 20 2018


Issued at 236 PM CDT Sun May 20 2018

A strong warm frontal boundary remains positioned over the Highway
34 corridor In Iowa to Illinois, where temperatures in the lower to
mid 70s contrast to east winds, low clouds, and temperatures in the
mid 50s to mid 60s over the northern 2/3rds.  A surface low pressure
center is over northeast KS, and will move up along this warm
frontal surface tonight into Monday.


.SHORT TERM...(This Evening through Monday)
ISSUED AT 236 PM CDT Sun May 20 2018

The seasonally strong warm front, surface low riding along it, and
seasonal moisture levels will support a widespread rainfall event
tonight into Monday.  The synoptic level forcing of the upper low
will help increase the stratiform coverage of rains, while
convective elements ride up into the rain shield.  That should keep
rains rates from being torrential, but will increase the likelihood of
a thick band of 1 inch plus amounts tonight into Monday. For now,
that seems most likely just north of the surface front, or roughly
from Ottumwa to the Quad Cities, to Rockford Illinois. This is well
handled by WPC`s day 1 QPF forecasts.  Severe risk seems very low,
as the forcing supports widespread precipitation, rather than discrete
cells.  Still, any isolated storm near the front, should that occur,
would need to be watch for low level rotation early this evening.

Monday, the forcing for rain will continue through the morning
hours, with dissipation from west to east between 10 AM and 2 PM.
There appears some late day modest heating possible, so we`ll only
undercut guidance a few degrees for now which reflects mid 70s west
to lower 60s northeast. Winds will be much lighter than today, as
the surface low will be overhead during the day.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 236 PM CDT Sun May 20 2018

Long term period will be dominated by weak upper level flow as
large stationary trough is forecast to remain across the SW CONUS.
Overall, ridging to weak SW flow will drive the weeks weather.
This will lead to a warming and moistening trend through the
week. Numerous waves will pass through the flow leading to chances
for showers and thunderstorms with each wave. Overall chances for
strong to severe storms will be tied to mesoscale features that
will not be resolved until the day of the storms.

First wave is expected to move into the area Wednesday into
Thursday morning.  Overall shear is weak with this system,
suggesting that organized updrafts will be difficult.  The
question now turns to rain.  PWs will be high, above 1.5 inches,
however there appears to be a lack in H85 flow that will lead
to the needed moisture transport.  Much like the past few days,
isolated heavy rain is possible, but not widespread.
This environment will remain in place until the end of the week,
when better chances for showers and thunderstorms will return
to the area.  From a sensible weather point of view, it will
feel a lot more like summer.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
ISSUED AT 638 PM CDT Sun May 20 2018

Dismal next 24 hours is in store for the area as clouds and rain
will encompass the area on the north side of a front that sits
from northern Missouri through central Illinois. While the
majority of the local area remained socked in with the IFR/MVFR
ceilings today, areas south of a line form KIRK to KBRL to KVYS
did see periods of clearing and are VFR for the time being. A
shortwave trough will move northeast across Missouri towards the
Great Lakes through the day Monday. With the front situated on the
southern part of the local forecast area, this will provide a
favorable set- up for precipitation development for much of Iowa,
northern and central Illinois into northern Missouri. Did back off
the timing by a couple hours in the terminal forecasts, but
confidence is still high that there will be widespread rain
showers with isolated to scattered thunder tonight. The low level
flow will be very weak on Monday after the system passes, so it
looks like most areas will struggle to mix out the low ceilings by
22.00Z. KBRL would be the first to see improvement, but again that
may not be until near 00Z. So kept the forecast quite pessimistic
with IFR or MVFR ceilings through much of the day Monday.




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