Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 291125
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
625 AM CDT Wed Mar 29 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 303 AM CDT Wed Mar 29 2017

The large storm system is on it`s way to the upper Midwest this
morning. At the surface, the low pressure is located in central
Oklahoma, with the main upper wave now sitting atop the New Mexico
and Texas border. This low is pumping up a seasonally high PWAT
airmass into the Missouri Valley, while drawing in a low level
cold conveyor across Iowa and Illinois. This will be a very active
warm frontal situation for our neck of the woods.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 303 AM CDT Wed Mar 29 2017

Today, clouds have already begun filling back in at low levels
overnight, as moisture from Lake Michigan has aided stratus
formation. So, under clouds and shallow cold advection, a blustery
and cool day is certain for our entire area. Just above this
stratus, strong warm advection is beginning to draw up the
moisture from the plains. By late afternoon, PWAT values over 1
inch are expected to move into the western CWA. Elevated CAPE
should remain low today and tonight, but enough should be
available in the south 1/3 or so for a mention of thunder up
through I-80 tonight. Looking at timing, the initial wave of rain
showers should move into the south this morning, and dissipate as
it moves northeast. Thus, a quick transition to categorical pops
is needed southwest, but a prolonged dry to chance level pop is
warranted northeast where today should stay dry and breezy through
early afternoon.

By late afternoon, and early evening, we will begin our strongest
period of forcing for this event. Surface winds over the northern
half of the area will be blowing around 20 mph gusting to 30 mph,
as in any good winter storm event, but this will move certainly be
a rain event. Other than this being rain vs snow, this event will
be a typical warm advection winter event. Moderate rain should
arrive in waves this evening and continue overnight, with PWAT
values supporting widespread rainfall of 0.50 to 1 inch by
morning. The highest amounts are possible in the southern counties
where convection is most likely. Locations could see around 1.5"
by morning where storms occur within the broad rainfall event.
Again, in treating tonight like winter event, 100% pops seem
warranted in the stratified rain event. The low level flow will
continue to sharpen the baroclinicity tonight north of the warm
front, as surface temperatures drop to the upper 30s, while the
south remains isothermal near 50.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 303 AM CDT Wed Mar 29 2017

At the beginning of the long term period, expect to have ongoing rain
and possibly isolated elevated thunderstorms.  Model consensus is
for a closed low to pass just south of the CWA during the day on
Thursday. As mentioned by previous discussions, H85 WAA will maximize
over the area leading to convergence across the CWA.  At the sfc,
guidance has the PWATs of near one inch will be across the area.
warm front just south of the CWA.  Any thunderstorms will be in the
vicinity of the sfc warm front. The better moisture transport at H85
will be east of the Mississippi River at 12z.  Thus the heavier
precip will be sliding to the east during the day. Overall rainfall
totals from 12z Thursday through Friday will range from 0.40 to 0.75
inches across the CWA.  As mentioned by other shifts, this rain will
likely lead to rises in area rivers.

The beginning of the weekend looks to be dry across the area.  The
next wave is forecast to be south of the area on Sunday.  The latest
trend in the guidance is for a southern shift in the QPF this Sunday
with the GFS south of the CWA and the ECMWF and GEM across the area.
If this trend keeps up, the whole weekend may be dry.  At this time
the current forecast has chance pops for Sunday.  This will be the
next area for improvement in the long term as we get closer to the
weekend.

Active pattern continues through next week with wave train still in
full effect across the central US.  Two waves in quick succession
will affect the area late Monday and into Tuesday and again
Wednesday into Thursday.  With a lack of run to run consistency, low
confidence on overall POPs across the area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
ISSUED AT 622 AM CDT Wed Mar 29 2017

Stratus from Lake Michigan will bring very low cigs to the area
this morning, with some visibilities in northeast Iowa falling to
around 1/4 mile at times. Otherwise, expect cigs about 200ft to
1000ft, today, with rain spreading over the entire region by 00Z
tonight. Some thunder is possible in southeast Iowa, but the over
all event should be rain, fog, and low cigs through tomorrow. East
winds will be windy, with 15 to 30 kts through the period.


&&

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

$$

SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...Ervin


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