Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 140834

Area Forecast Discussion
National Weather Service Quad Cities IA IL
234 AM CST Wed Feb 14 2018

Issued at 230 AM CST Wed Feb 14 2018

Skies were clear across much of the cwa except our far south where
that area was on the northern edge of a cirrus shield.

Early morning temperatures ranged wildly depending on wind
conditions. At locations that have a south wind varying from 5 to
15 mph temperatures were in the mid 20s to lower 30s. Where the
wind was calm in valley or sheltered areas readings were as low as
12 above. This is exactly what I alluded to in my afd written 24
hours ago. HAASE


.SHORT TERM...(Today and Tonight)
ISSUED AT 230 AM CST Wed Feb 14 2018

Continued south to southwest winds during the short term will
gradually bring an increase in low level moisture (combined with
snow melt) below a strengthening low level inversion. This will
lead to increasing chances for at least patchy fog and drizzle
later this afternoon, then perhaps more widespread fog and some
drizzle tonight. However, not confident yet on how dense this fog
may become or coverage of drizzle, for later shifts to evaluate.

Based on temperatures yesterday exceeding expectations, I will go
along with guidance in even warmer temperatures this period.
Afternoon highs should push into the 40s today, while lows tonight
will be mainly in the 30s.  HAASE

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 230 AM CST Wed Feb 14 2018

The long term forecast remains a period of significant temperature
variance, but dominated by mild air for the most part. Thursday
continues to look like a great melting day of snow,  with surface
dewpoints pushing well into the 40s. The deeper moisture is shunted
a bit farther east than any model data indicated yesterday, thus the
pops are both delayed towards late morning and afternoon, and
focused in the east with anything other than lower chances.  This
reduces the unlikely icing event that our blended model data
resulted in over the past few days. Fog on the other hand, continues
to appear likely Thursday morning, possibly through early afternoon,
as weak convergent flow at the surface combine with saturated snow
melt air and dewpoints well above freezing.  That could be a
headlined dense fog event, and will begin addressing that in the HWO
now that confidence is growing on the fog threat.

Thursday night, moisture sweeps out of the area, as a cold front
arrives, cooling us into the teens and 20s, as this is still a snow
covered CWA for the most part at that time.  The same will be true
for  a cold Friday in the upper teens to upper 20s, but by the
weekend, the next warm up looks to possibly wipe out most of our
snow pack.

After a weak, possibly light snow producing wave moves by Saturday
afternoon, we should be in sustained southwest flow again through
Monday. Our extended model procedures result in more snow than is
likely given the mild model data forecast by the 00z suite of data.
This event should be mainly a rain producer Monday.  Looking at
Tuesday and Wednesday, the models are split on whether to bring
through a cold front, drying things out, or developing a second wave
into low pressure. In any case, low pops for snow are forecast, with
temperatures near normal.



.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1140 PM CST Tue Feb 13 2018

Brief periods of MVFR visibilities of 3-5sm possible at the TAF
sites overnight through daybreak. Otherwise, predominately VFR
conditions expected through much of Wed AM. Some low clouds to
our south will likely lift N/NE and brush the Mississippi River
terminal sites from south to north by late morning through late
afternoon. Anticipate a several hour period of mostly MVFR
ceilings before likely lifting away. This may set the stage for
fog development and low stratus Wed night. A lot of uncertainty
on timing and extent at the terminals, so for now I wrote to
MVFR category mainly on visibilities Wed eve, but could rather
variable conditions from VFR to IFR.




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