Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 290426
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1126 PM CDT WED SEP 28 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 340 PM CDT Wed Sep 28 2016

Vertically stacked upper low seen on satellite movie loops
spinning over northern Indiana was spreading stratocumulus/stratus
as far west as the Dakotas/MN border and far western IA. Under
this canopy of clouds temperatures in the dvn cwa were rather
cool, in the upper 50s to lower 60s. Scattered showers were
located in southern WI and northern IL and were moving southwest.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 340 PM CDT Wed Sep 28 2016

Forecast focus on cloud trends and temperatures.

Tonight: Any scattered showers or sprinkles should end by 7 pm
according to the HRRR with much of the night dry. Satellite loops
indicated clearing taking place in eastern WI as drier air rotates
around the upper low. We will be going with the idea this clearing
trend will spread southwest into the dvn cwa overnight. Therefore,
skies should eventually become clear or partly cloudy at most
locations. The center of the low should push southward into
southern Indiana by sunrise with high pressure ridge extending
from northern MN to the TX panhandle. Minimum temperatures will
range from the mid 40s to the lower 50s.

Thursday: Models suggest the synoptic pattern to become locked in
place with the closed upper low becoming stalled in far southern
IN or western KY, with the surface ridge from MN to TX. Most of
the cwa will enjoy sunshine especially west of the MS River closer
to the ridge. However, northeast winds coming off Lake MI due to
the cyclonic circulation around the low should spread low clouds
back into our eastern cwa. There may also be a small chance of
showers or sprinkles in our far eastern counties. Temperatures
should be warmer with highs around 70 at most locations.

.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 340 PM CDT Wed Sep 28 2016

Thursday Night...Vorticity maxima begin to pinwheel around Ohio
Valley upper-low, making westward progression back into E Iowa/
NW Illinois/and NE Missouri. Sensible weather effects will be
limited. We`ll have increasing low clouds, and a slight chance for
light showers across the far east - primarily in Bureau and Putnam
Counties.

Friday and Saturday...Models have converged on low retrograding
further NW. Went cooler for max temps, below the SuperBlend, to
account for reduced solar insolation from low stratus. Mid to upper
60s are the current going forecast but further downward adjustments
remain possible. Winds are forecast to be strongest on Friday,
between 10-20 mph (isolated higher gusts) out of the NNE.

Precipitation: Isolated to scattered showers are likely at times.
The highest PoPs are over the eastern half of the CWA and peak
between 40-50% Friday afternoon through Saturday. Further west,
chances are lower and many locations may receive little to no
measurable rain.

Sunday and Monday...Model suite in reasonable agreement weakening
the upper-level low on Sunday and tracking it to the NE through
Michigan. This will be a dry stretch of weather with temps in the
70s.

Tuesday and Wednesday...Pattern transitions into a warmer, return
flow scenario. Dewpoints may rise into the 50s; however, the best
moisture advection will probably occur on Wednesday as it pools
along a cold front. May need to remove shower chances over the
west in future updates because forcing and low-level convergence
are negligible. Wednesday...showers and thunderstorms may
accompany the front but it is too early to assess the severe
potential and coverage of storms. ..Uttech..

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
ISSUED AT 1125 PM CDT Wed Sep 28 2016

VFR conditions to prevail the next 24 hours. Upper low to the east
to result fair to partly cloudy skies with any bases above 3K AGL.
Winds will be northerly at 5 to 10 MPH overnight and 10 to 20 MPH
on Thursday, decreasing to 5 to 10 MPH by sunset.

&&

.HYDROLOGY...
Issued at 100 PM CDT Wed Sep 28 2016

Overview: Most significant change was at New Boston on the
Mississippi River where the crest forecast increased from moderate
to major flood stage. Otherwise, river forecasts are largely on
track. See site specific information in the following discussion and
in recent Flood Warning Statements.

Cedar River...

Vinton: Now below major flood stage.

Cedar Rapids: Forecast to fall below major flood stage Thursday
evening or night.

Conesville: Major flooding is occurring as river level rises
rapidly. Timing of crest forecast is Thursday afternoon into
Thursday night. Confidence is moderate to high on a crest a half
foot on either side of 18.30 feet.

Wapsipinicon River...

Anamosa Shaw Rd: Forecast to fall below major flood stage this
evening.

De Witt 4S: High confidence in reaching major flood stage. Thinking
current crest forecast is on the upper end of possible outcomes.
Reasonably high probability the final crest is lower. Please
monitor for updates.

Iowa River...

Excessive amounts of water continue to propagate downstream through
the Iowa and Cedar Rivers. There is high confidence on significant
flooding. Exact timing varies by site.

Moderate confidence is associated with the crest forecasts. Current
thinking is crest forecasts are toward the upper range of what is
possible; observed crests may come in lower. Please follow forecast
information closely throughout this event.

Mississippi River...

Minor to Major flooding continues to be on track. Greatest forecast
change was at New Boston with an increased crest forecast from
moderate to major. Otherwise, latest forecasts show little to no
adjustments. Majority of the crests are projected to occur over the
weekend or early next week. Uttech

&&

.DVN Watches/Warnings/Advisories...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Uttech
AVIATION...Nichols
HYDROLOGY...Uttech



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