Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 141755
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1255 PM CDT Fri Jul 14 2017

...18Z AVIATION UPDATE...

.UPDATE...
Issued at 1035 AM CDT Fri Jul 14 2017

This morning, low level stratus has been slow to break up as it
moves south with the flow. As a result, have changed sky forecast
and dropped highs across the northern CWA. Went with a consensus
of the short term models for highs as they have the best trend
currently. As a result, NW IL and NE IA will struggle to reach the
low 70s today. When clouds finally break, it should be a
beautiful day

&&

.SYNOPSIS...
Issued at 325 AM CDT Fri Jul 14 2017

Skies were clear across most of the dvn cwa except for some cirrus
moving eastward in our far southern counties. Upstream in MN and
WI there is extensive low stratus, due to plenty of low level
moisture seen on 00z/14 soundings at KGRB/KMPX. These clouds were
gradually spreading south.

3 am temperatures were in the 60s in the cwa.

High pressure was situated over the eastern Dakotas and northern
MN where temperatures were in the upper 40s to lower 50s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 325 AM CDT Fri Jul 14 2017

Forecast challenge will be clouds and temperatures.

Today: High pressure will be building into the cwa from the
northwest as the day progresses. This will supply mostly sunny
skies to much of the cwa. However, there is a cool pocket aloft
that will rotate from the north over far northeast IA and nw IL.
Skies should become partly sunny and even mostly cloudy for a
time in that area. Maximum temperatures will range from the lower
70s from Dubuque to Freeport areas, to the lower 80s in our far
southern cwa.

Tonight: High pressure will settle over the cwa with clear skies
and light to calm winds. This should bring a pleasant night with
lows in the mid 50s to around 60 at most locations. There may be
some patchy fog, especially in valley/low spots but have not
included in the grids at this time.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 325 AM CDT Fri Jul 14 2017

Surface high pressure and a northwest flow aloft will keep dry
weather and near normal temperatures going into Saturday. A weak
front and moisture convergence will bring back a small risk for
thunderstorms and noticeably more humid conditions Saturday night
into Sunday. Next week, the upper level ridge and building heat over
the western U.S. nudges eastward, pointing toward a return of hot
and very humid conditions by mid to late week, with attendant low
confidence chances for several rounds of thunderstorms.

Saturday night into Sunday, a shortwave rotating into the great
lakes sends a frontal boundary southward into eastern IA and
northwest IL Sunday morning, which is shown meandering slowly south
through the forecast area Sunday. Moisture pooling along this
boundary is shown sending dewpoints back into the upper 60s to lower
70s. While upper level forcing is focused largely to the north and
northeast of the local area, there will likely be enough instability
from the pooling moisture and at least marginally supportive bulk
shear to justify slight chance pops for convection along this
boundary, especially over the east Sunday afternoon.

Next week, the upper level ridge and associated axis of very warm
air aloft out west spreads eastward, setting up a typical July ring
of fire pattern by mid to late week. Have continued to nudge highs
above model blends that were heavily influenced by what looks to be
unrealistically too cool GFS/CMC highs, which were running several
degrees below the warmer ECMWF. Thus have highs reaching the upper
80s to lower 90s by Wed and Thu, which may still be too cool. At the
same time, dewpoints returning into the 70s, assisted by convergence
along a surface boundary, will likely push heat index readings well
into the 90s, if not 100 plus. With the boundary likely setting up
over or near the area, there will be a potential for thunderstorms
in or near the forecast area from late Tuesday onward, but
confidence in timing and coverage is low this far out.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
ISSUED AT 1255 PM CDT Fri Jul 14 2017

Stratus associated with cold advection and high pressure moving
into the area led to MVFR cigs across the northern CWA. This
should continue through most of the early afternoon. Otherwise,
VFR conditions are expected through the next 12 hours or so.
Overnight, expect MVFR vsbys and possibly IFR at DBQ towards
sunrise.

&&

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

$$

UPDATE...Gibbs
SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Sheets
AVIATION...Gibbs



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