Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 200835

Area Forecast Discussion
National Weather Service Quad Cities IA IL
335 AM CDT Tue Mar 20 2018

Issued at 318 AM CDT Tue Mar 20 2018

Eastern Iowa and western Illinois remain in the band of strong
subsidence, between the low pressure circulation to the southeast,
and the inverted trof forcing located along the Missouri River. This
is bringing a rather strong northeast wind to the area, which is
still higher than models suggest it should be.  2 AM winds remain in
the 15 to 18 kt sustained range, with some gusts into the lower 20s
east.  The mixing and high cloud cover thus far have not allowed
temperatures to drop much below 29.


.SHORT TERM...(Today and Tonight)
ISSUED AT 318 AM CDT Tue Mar 20 2018

Today`s weather seems rather straight forward, but not very
pleasant. The northeast flow will gradually weaken during the day,
but the continued cold advection under mid and high cloud cover
will not allow much of rise in temperatures today. Highs will be
limited to the lower 40s in most locations, with some upper 30s
likely north. Dry weather will continue through tonight, as the
inverted trof remains west of the local area, and with it, any low
level saturation. Winds today will gradually weaken after mid
morning, and by late afternoon, they should fall below the breezy
category, making for a more pleasant end to the day. Tonight,
under thin cloud cover and light winds, lows should dip to the
lower to mid 20s.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 318 AM CDT Tue Mar 20 2018

Wednesday and Thursday

Consistent signal in the models for a band of light rain to affect
the southwest and southern forecast area on Thursday. Later
shifts may have to increase precipitation chances to the likely
category. For temperatures, expect highs near normal on Wednesday,
then slightly above normal Thursday.

Friday and Saturday

Widespread precipitation expected across parts of the Midwest Friday
Night into Saturday near a strong NW to SE oriented low-level
baroclinic zone. There will likely be a QPF band of 1" or more.
It is just too early to know exactly where the heaviest of this
band will focus and where the rain/snow line will set up.

Not too uncommon for an early spring system, the forcing for this
event will be dominated by an elevated zone of frontogenesis. And
in this case, displaced well to the northeast of the surface low
track. Convection is also possible due to elevated instability;
for now have slight thunder chances in the south Saturday AM.

Model Trends and Confidence:

Models have come into a little better agreement on the track of what
should be a weakening surface low, taking it through northern
Kansas to NW Missouri before it begins to drift more to the
southeast. The ECMWF is the strongest with the low at 998mb, the
CMC and GFS are slightly above 1000mb.

Based on wetbulb temperatures at the surface and aloft, the GFS and
ECMWF are cold enough for a period of moderate to heavy snow
across at least the northern third of the forecast area, possibly
even further south. The CMC isn`t as cold, favoring a period of
snow only in the north. Our current forecast is a conservative
blend with highs in the upper 30s north to upper 40s south and a
rain/snow mix down to the counties along I-80.

Overall, confidence is low on impacts for the forecast area,
mostly because there is a lot of time yet for models to shift the
exact track of the low. Furthermore, the northern gradient of the
precipitation will likely be very tight over a short distance.
And it`s too far away to forecast where this gradient will be.
Keep up with the forecast this week as changes are likely.

Sunday On

The GFS is out of phase with the CMC and ECMWF, bringing the next
system in on Sunday as opposed to next Monday night into Tuesday.
Have 30-50% chances for precipitation for most areas on and off
through this period due to the uncertainty. Nonetheless, it
appears the active weather will continue into next week. Uttech


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
ISSUED AT 1247 PM CDT Mon Mar 19 2018

VFR conditions are expected throughout with decreasing northeast
to north surface winds and only mid to high level cloud cover.




LONG TERM...Uttech
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