Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 181031

Area Forecast Discussion
National Weather Service Quad Cities IA IL
531 AM CDT Sun Mar 18 2018


Issued at 310 AM CDT Sun Mar 18 2018

The stratus has continued to very slowly clear out as it moves south
and west overnight. That has then led to fog formation, as the
earlier cloud cover allowed for dewpoints to remain in the lower 30s
just prior to clearing. The fog is locally dense, and spotters have
reported dense fog as far northeast as eastern Linn / western Cedar
Counties.  I have already issued an dense fog advisory to get the
message out on the dense fog.


.SHORT TERM...(Today and Tonight)
ISSUED AT 310 AM CDT Sun Mar 18 2018

The stratus edge as of 230 AM, is located from near Ottumwa to near
Quincy.  While fog and new stratus may form yet this morning, this
edge seems important for where clearing today should occur most
efficiently. I expect the dense fog to continue to expand very
slowly, and that may require an expansion in the advisory counties,
but what`s out now is already having a buffer of one county from
where the impacts are most notable. In any case, the strong mid
March sun will begin to thin out the fog and shallow stratus by 9
AM, and by 10 AM, aggressive thinning should be ongoing or
completed. The dense fog advisory will run through 10 AM this
morning. By early afternoon, all areas should see partial to full
sun, like yesterday in the north. With light winds, that should make
for the "best" day this next week with temperatures in the lower to
mid 50s, and light winds.

Tonight, high clouds will spread over the region as the next low
pressure takes shape to the south of Iowa. That low will not be
close enough to bring any precipitation, but will help keep
temperatures a bit warmer under the high cloud cover tonight.

.LONG TERM...(Monday through Saturday)
ISSUED AT 310 AM CDT Sun Mar 18 2018


Models have converged on track of a cut-off upper low remaining well
south of the forecast area - tracking from NE Oklahoma through
southern Missouri into Kentucky. Only have slight chances for light
rain south of highway 34 (west of Galesburg, IL). If the southern
trend continues, will have to remove precipitation chances
completely in later updates. While it will likely be dry on Monday,
we won`t escape the breezy conditions. ENE winds of 15-20 mph with
gusts up to 30 mph are anticipated through the day.

Tuesday through Thursday

A longwave trough will deepen over the eastern third of the U.S.
leading to colder weather (highs in the 30s and 40s) for the Upper
Mississippi Valley. On the western periphery of the longwave trough,
models have a weakening disturbance approaching E Iowa/NW Illinois
on Tuesday. Latest guidance suggests the better chance for light
rain and snow showers is over central and western Iowa. Locally,
have slight chances over far western sections of the forecast area.

For Thursday, the GFS is an outlier breaking out widespread
isentropically forced precipitation, especially later in the day and
at night. Our current forecast is much more conservative with only
slight chances for measurable precipitation. The ECMWF/CMC are
totally dry.

Friday and Saturday

Active pattern setting up for the end of the week into next weekend.
Strong and deep layer warm air advection may result in widespread
precipitation, especially Friday afternoon and night. And elevated
instability may lead to isolated thunderstorms. For now, only
mentioned slight chances for thunder well south of I-80.

A lee-side low is forecast to form in eastern Colorado early Friday
and then track through the Midwest along an impressive baroclinic
zone that features spring warmth (60s and 70s) to the south and
winter cold (20s and 30s) to the north. Forecast confidence on
precipitation types, amounts, and timing are low. With that said,
thermal profiles suggest mainly rain across the majority of the
forecast area. An exception is the north or northeast where the GFS
and CMC are colder than the ECMWF. In this area, there is a
possibility for a wintry mix or period of snow. Don`t want to get
too much more into the details this far out - expect changes to the
forecast over the coming days. Uttech


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
ISSUED AT 528 AM CDT Sun Mar 18 2018

Light winds and clear skies will dominate the next 24 hours, but
to start the period, there is shallow dense fog covering much of
eastern Iowa and western Illinois. As of 11Z, this dense fog is
not directly impacting any TAF terminal, but it remains a
possibility through about 15Z/18. In addition, there is a large
stratus deck over central Iowa, with MVFR cigs. That stratus will
need to be watch, but is currently expected to stay west of
eastern Iowa airports.


IA...Dense Fog Advisory until 10 AM CDT this morning for Benton-Cedar-
     Des Moines-Henry IA-Iowa-Jefferson-Johnson-Keokuk-Lee-Linn-
     Louisa-Muscatine-Van Buren-Washington.

IL...Dense Fog Advisory until 10 AM CDT this morning for Hancock-

MO...Dense Fog Advisory until 10 AM CDT this morning for Clark.



LONG TERM...Uttech
AVIATION...Ervin is the U.S. government's official web portal to all federal, state and local government web resources and services.