Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 302025
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
325 PM CDT Sun Apr 30 2017

.SYNOPSIS...
Issued at 325 PM CDT Sun Apr 30 2017

Large occluded cyclone centered over Kansas continues to dominate
the weather over the region this afternoon. The low at the surface
was centered over south central KS with a large comma head and
arching band of showers from its northwest across NE, southern IA
central IL to a line of strong storm from the TN Valley to the
Gulf along the occluded front. The local area remains on the cool
side of the system with low clouds, brisk northeast winds,
temperatures in the 40s and a band of light to moderate rain from
roughly Marshalltown to Galesburg. The associated warm front was
not far to the south across northern MO into central IL.

&&

.SHORT TERM...(Tonight)
ISSUED AT 325 PM CDT Sun Apr 30 2017

Near term focus remains on the front to the south and potential
for strong to severe storms this evening as the system begins to
lift northeast. MSAS surface pressure analysis at 19z showed a
developing low along the occluded front over central MO under the
dry slot where sufficient sunshine was causing destabilization.
Area radars showed a rapidly developing line of showers and
thunderstorms along and north of this central MO low. This
feature is expected to lift northeast across our far southeast
counties early this evening. This area will have more than
adequate deep shear for severe storms, but the amount of
instability remains questionable and dependent on sky trends over
the next several hours. Latest SPC day one outlook has zoned in on
this area ahead of the central MO convection with a marginal risk
and will be watching trends closely over the next several hours.

Beyond, this dry slot and surface boundary lift through the
forecast area overnight, likely accompanied by one or more bands
of showers and isolated thunderstorms in the evening. This then
transitions to patchy light rain, drizzle and fog overnight as
winds fields go light and moisture becomes more shallow in the
column. Temperatures may rise a few degrees as warm advection
kicks in this evening, leading to evening highs for the calendar
day in the mid to upper 50s across the southeast, then near
steady to slowly falling temperatures through the 40s overnight.

.LONG TERM...(Monday through Sunday)
ISSUED AT 325 PM CDT Sun Apr 30 2017

Forecast focus on light rain and very cool to start the month of May
and then mainly dry with a slow temperature rise to normal by next
weekend.

Monday and Monday night: Occluded cyclone early Monday over Iowa
will lift to the northeast and be located in extreme northern WI by
the late afternoon, and then south of James Bay by sunrise Tuesday.
With the system occluded the deeper moisture will have been shunted
well to our east. The dvn cwa will be squarely in the chilly,
cloudy, rainy cyclonic flow around the large upper low. In addition,
west winds will be gusting to around 30 mph, possibly to 35 mph.
This will add a chill to the air, especially considering afternoon
high temperatures will be only in the upper 40s to lower 50s. This
is about 15 to 20 degrees below normal for May 1. Minimum
temperatures Monday night should dip into the upper 30s to lower 40s.

Rainfall:  We will have likely pops for much of the morning on
Monday with diminishing pops from south to north during the
afternoon and evening. The rain should end along Highway 20 by early
Tuesday. Additional rainfall should be less than 2 tenths of an
inch.

Tuesday through next weekend: Northwest flow aloft will bring a
mainly dry period to the dvn cwa. During the mid to late week the
ECMWF/GFS do indicate a decent storm system tracking from the
southern Plains into the Ohio Valley. However, this is progged to
remain south and east of the dvn cwa but could get close. Meanwhile,
temperatures will remain below normal for much of the new work week,
with highs mainly in the lower 60s and lows in the lower 40s.
However, by next weekend temperatures should finally rise to 70+ at
most locations, which would be close to normal for early May.
Haase

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 115 PM CDT Sun Apr 30 2017

Large storm system over the central U.S. will continue to affect
the terminals throughout as it slowly lifts northeast. Widespread
IFR conditions with gusty northeast winds will continue this
afternoon with a couple bands of showers and a few thunderstorms
pushing northeast through the area. Have limited the mention of
thunderstorms to the BRL terminal for now, which will be closer to
a more favorable environment for thunderstorms late this afternoon
and evening. As the surface low lifts northeast through central
Iowa, surface winds will back to the south and then southwest with
the passage of a warm front. Low ceilings, likely at IFR levels,
and MVFR fog will continue to be an issue tonight into Monday
morning at all sites.

&&

.HYDROLOGY...
Issued at 1153 AM CDT Sun Apr 30 2017

Heavy rain failed to materialize in northeast IA and far nw IL
with the heaviest rain remaining to the south and east. Therefore,
forecasted crests on the Mississippi River from the Quad Cities to
Muscatine have been lowered to only minor flooding. Farther downstream,
mainly moderate flooding is still expected.

On the Wapsipinicon River near De Witt the crest was lowered to
right at moderate flooding, which is 11.5 feet.

A flood warning was issued for the Green River at Geneseo as
forecasted rains of over 1/2 inch this afternoon and evening should
push the river into minor flooding.

Looking ahead: Some light rain is expected on Monday but the
remainder of the new work week and into next weekend look dry.
Temperatures will also be pushing into the 60s. Haase

&&

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

$$

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



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