Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 121745
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1145 AM CST Mon Feb 12 2018

...18z AVIATION UPDATE...

.SYNOPSIS...
Issued at 234 AM CST Mon Feb 12 2018

A 1044 mb high pressure system was centered in ND and was
providing clear skies and rather light winds to the dvn cwa.
Early morning temperatures ranged mainly in the single digits
below zero to the single digits above zero.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 234 AM CST Mon Feb 12 2018

Forecast focus on cold but quiet conditions.

Today: High pressure centered across the Upper Mississippi Valley
will supply sunny and cold weather to the area. Highs will be in
the teens to lower 20s, as light nw winds veer ne.

Tonight: The center of the highs slips into lower MI so we start
out clear early in the evening. However, later in the evening into
the overnight hours warm air advection kicks in. Increasing
mid/high level clouds is expected to spread from west to east
over the cwa. This is already evident on GOES-16 satellite out to
our west in the western Dakotas and western NE. Light east to
southeast winds and thickening cloud cover (as seen on time height
sections) will keep temperatures warmer than early this morning.
Lows should drop into the single digits to around 10 above zero.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 234 AM CST Mon Feb 12 2018

The extended forecast remains focused on a warm up for Wednesday
through Thursday, followed by a brief cool down for Friday, then
another milder weekend.

The initial warm up remains very low confidence, as models continue
to forecast a huge warm up for by Wednesday and Thursday, while also
dropping us below freezing Wednesday night.  This is a problem.  We
have 5 inches of snow depth reported yesterday in Keokuk Iowa. The
rest of the area has 6 to 12 inches snow depth, that after tonight,
is very very cold after lows below zero.  Today`s chilly
temperatures will be followed by another night in the single
digits. That leaves a deep cold snowpack in place for Wednesday
and Thursday. Models push highs wednesday to the upper 40s to mid
50s! Unless we have dewpoint that match that level, that just seem
impossible. I have lowered highs considerably from guidance, and
am likely still too high for Wednesday, with upper 30s to mid 40s.
As the warm air arrives, we`ll almost certainly fire off a
stratus deck, or fog, or both. That will melt snow certainly, but
probably keep our warming aloft, and not at the surface. So, a
more likely scenario might be mid to upper 30s Wednesday, with
lower to mid 30s at night, followed by 30s again Thursday. Fog is
possible, maybe dense, through this period as well.

Pops are dry wednesday night through 12Z, then jump to 20-40% for
Thursday morning. Because we run hourly weather forecasts from 6hr
pops, that results in a forecast of freezing rain/sleet early
thursday morning.  This is possible, but a low probability given
that pcpn will likely onset later in the morning as opposed to 8 AM.
We will keep the HWO on low probability of hazardous weather. The
rain chances Thursday are rather meager in reality, as only the
ECMWF saturates this far north for more than a few hundredths.

Beyond, a cold front arriving Thursday will bring a colder day
Friday in the upper teens to mid 20s.  After this, a transition to
zonal flow again will bring back highs to the 30s, and possibly
40s for the weekend.

ERVIN

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1140 AM CST Mon Feb 12 2018

A VFR TAF cycle through Tue morning under passing high pressure
with just rounds of high clouds and some mid decks toward Tue
morning. North to northeast sfc winds of 5-10 KTs to become
light and variable overnight, then veering to the southeast and
increasing again 5-10 KTS by mid Tue morning.   ..12..

&&

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

$$

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Ervin
AVIATION...12



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