Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 150331
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
931 PM CST Wed Feb 14 2018

.UPDATE...
Issued at 914 PM CST Wed Feb 14 2018

Dense fog confined mainly to areas east of the Mississippi River
being in closer proximity to weak surface ridging and lighter
winds. As the weak ridging moves away and SW winds pick up
however, we could see additional improvement in visibility in
these areas late this evening into the early overnight. Thus,
much of the overnight could have only just patches of dense fog
mainly east of the Mississippi River, more widespread further
east/southeast into IL. However, some of the latest hi-res
guidance supports dense fog becoming widespread again late
tonight through Thursday morning ahead of an approaching low
pressure system and warm front, and expanding to include areas
further west/south of the current dense fog advisory. This makes
for a challenge in messaging and handling of headline, but feel
probably best to leave the advisory as is for now and just
mention that some improvement likely but expect more widespread
dense fog late tonight and Thursday AM.

&&

.SYNOPSIS...
Issued at 316 PM CST Wed Feb 14 2018

Skies were mainly clear across the north, with an area of low
stratus and fog that was spreading north across the central and
southern forecast area this afternoon.

Temperatures remained cooler across the far north, but still
warmed into the upper 30s, with temps into the low to mid 40s
across the south. Winds were generally out of the south at around
10 to 15 mph. Some sites saw visibilities drop to around 3 to 5
miles in the fog.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 316 PM CST Wed Feb 14 2018

Fog and low clouds and some light drizzle/rain chances the main
focus through the short term. WAA and moisture advection has been
ongoing today and is expected to continue across much of the
forecast area tonight. Dewpoints into the mid 30s to low 40s
already across the forecast area with values expected to remain
similar or slightly increase overnight. This will keep lows mild
and bring the potential for fog with the high dewpoints over the
snowpack and especially into late tonight/early Thursday with a
boundary sinking into the area and winds expected to diminish.
Have already had visibilities dropping into the 3 to 5 mile range
at many sites, with a few spots dipping to around 1 mile at times
this afternoon. Hi-res models indicating decent chance for
widespread visibilities or around 1 mile or less across much of
the area by late evening through the early morning hours. Fog
would then start to lift/clear out from northwest to southeast
Thursday morning as the cold front moves through the forecast
area. Some weak lift along and ahead of the frontal boundary into
Thursday could allow for some chances of light rain, overall
better precipitation chances are expected further south and east
into Illinois. Placement of the fog and exactly how dense the fog
may get for tonight are still in question. Therefore will continue
to highlight the potential in the grids and leave it for the
evening shift to make any headline decisions regarding the
possibility of a dense fog advisory.

.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 316 PM CST Wed Feb 14 2018

Upper trough to quickly shove south across the area Thursday night
with an area of sfc high pressure building into the region
Friday. This will bring dry conditions and cooler temperatures as
the cool air remains in place behind the front that moved through
late Thursday. A large upper trough to then dig into the region
for Saturday which could bring a chance for some light snow across
the far north Saturday morning, then chances for precipitation
spread across southeastern IA/WC IL into Saturday afternoon. A
more robust trough expected to dig into the western US by Monday
with southwest flow aloft across the area through the early to
middle portion of next week. This suggest a slightly more active
time period with precipitation chances expected Monday into
Wednesday. An inverted trough feature with an area of low pressure
situated across NE KS into central IA will be situated across the
forecast area. This should allow for much of the precip chances
Monday to be rain across the state, with the boundary moving ESE
into Tuesday and Wednesday. Additional energy to eject
northeastward from the western US trough bringing additional
chances for precipitation Tuesday into Wednesday. Colder air to
move into the area so precip is expected to changeover to all snow
by Monday night into Tuesday with precip then beginning to exit
the area into Wednesday.

As for temperatures expect the mild conditions into Thursday, with
colder air moving and temps dropping through a portion of the day.
Colder temps then expected into Friday with a warmup for the
weekend ahead of the system for Monday. By Monday could see temps
back into the 40s to mid 50s, with a cool down again for Tuesday
into Wednesday as the next push of cold air moves into the area.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 543 PM CST Wed Feb 14 2018

Challenging set of TAFs with likely variable conditions across the
region. Moisture advection and additional moisture from snowmelt
will aid in areas of stratus and fog with IFR to LIFR/VLIFR at
times across the terminals. Initially this evening at all but BRL
will be favored for the low conditions. Then some improvement may
occur at these sites by late evening into the overnight with
increased SW winds. However, the low conditions are expected to
redevelop at BRL and spread back north across much of the
terminals late tonight and Thursday as a warm front lifts north.
In summary, mostly MVFR conditions dominate through the TAF cycle
due to fog, with bouts of IFR to LIFR/VLIFR at times.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Dense Fog Advisory until 9 AM CST Thursday for Cedar-Clinton-
     Delaware-Des Moines-Dubuque-Jackson-Johnson-Jones-Lee-Linn-
     Louisa-Muscatine-Scott.

IL...Dense Fog Advisory until 9 AM CST Thursday for Bureau-Carroll-
     Hancock-Henderson-Henry IL-Jo Daviess-McDonough-Mercer-
     Putnam-Rock Island-Stephenson-Warren-Whiteside.

MO...NONE.
&&

$$

UPDATE...McClure
SYNOPSIS...Haase
SHORT TERM...Beerends/DMX
LONG TERM...Beerends/DMX
AVIATION...McClure



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