Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200020
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
720 PM CDT Sat May 19 2018

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 220 PM CDT Sat May 19 2018

Rather complex weather scenario ongoing today. Weak surface flow
due to weak synoptic forcing made identifying frontal boundaries
difficult. Thunderstorms from overnight across central MO kept
clouds across the area early this morning. These clouds quickly
cleared out and lead to sufficient warming across the area.
Numerous MCVs were identified on the satellite this afternoon.
One, across central IA, led to the redevelopment of thunderstorms.
This will be one area to watch through the early short term
period. Another area will be NE KS where better flow and
instability will lead to the development of thunderstorms. These
storms could track towards the area later tonight.

&&

.SHORT TERM...(Now through Sunday)
ISSUED AT 220 PM CDT Sat May 19 2018

Water vapor verified the existence of an H5 wave moving north
through the flow into NE KS and NW MO. This coupled with a MCV
south of DSM lead to showers and storms this afternoon. These
storms will likely move north and expand across a surface
boundary. These storms will likely expand into the far western
zones. Gusty winds and small hail may be possible with these
storms. The threat for severe weather appears low with these
storms.

Latest HRRR runs have come in line with the 12z NAMnest,
suggesting upscale growth into a MCS tonight. While the flow is
weak overall, HIRES guidance suggests that H85 flow may increase
with MCS leading to a favorable environment for organized storms.
If this occurs, then there would be a tornado threat along with
the wind threat from the MCS tonight. Again, with weak forcing,
convection may not occur this way. We will need to watch for
convection forming anywhere in the warm sector.

Tomorrow, weak flow continues across the area. With boundaries
south of the area, thunderstorm development looks likely. Moderate
rain will likely occur across the area. A marginal risk for severe
weather is forecast across the far southeastern CWA.

.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 220 PM CDT Sat May 19 2018

Monday: Scattered showers are possible as the 500 mb shortwave
that is expected to bring thunderstorms over the region on Sunday
moves to the east. At 12Z Monday, the GFS/ECMWF are in agreement
in moving an energetic longwave trof on shore into southern
California and closing it off over Nevada. An upper level ridge
will build over the midwest in response to this energy moving
onshore. Surface high pressure will also begin to build into the
region from southern Canada, bringing with it pleasant weather.
High temperatures on Monday will be in the 70s, with overnight
lows in the 50s across the north, to around 60 in the south.

Tuesday: Surface high pressure will continue to build into the area
beneath the east side of the upper level ridge axis. This will make
for a dry and warm day with high temperatures expected to be around
80 in the north, with mid 80s over the south. Overnight lows will be
in the 60s.

Wednesday through next Saturday: Longer range models prog the upper
flow aloft to shift to the southwest as and upper ridge shifts east.
Confidence is low in timing a series of weak shortwaves progged to
move through this flow, bringing with them a chance of showers and
thunderstorms each day. Humidity levels will be on the rise as a
southerly flow at the surface advects warm and moist air into the
upper Mississippi Valley from the Gulf of Mexico. The combination of
temperatures in the 80s and dewpoints in the 60s will make for muggy
conditions. ..Kuhl..

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 655 PM CDT Sat May 19 2018

A frontal boundary is in play for the next 24 hours with rain,
thunder potential through tonight, followed by MVFR OR IFR
ceilings through at least the morning hours on Sunday. There is
considerable uncertainty with the showers and thunderstorms
tonight, so while there remains a good chance to see some
shower/thunder activity near all terminals, the timing is unclear
so used most probable timing. Throughout tonight, the front will
be dropping southward and remain south of the area through the
day. Winds will shift to the east/northeast and ceilings will
drop. IFR/MVFR ceilings are expected then and while models
indicate they could persist through Sunday evening, think that
might be too pessimistic and so did start to break the clouds up
by mid afternoon from south to north.

&&

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

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Kuhl
AVIATION...Brooks



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