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afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
340 am CDT Tue Oct 24 2017

Synopsis...
issued at 320 am CDT Tue Oct 24 2017

Deep low pressure (986 mb) was located north of Presque Isle Michigan.
Meanwhile cold Canadian high pressure (1042 mb) was centered
over the northern rockies. The pressure gradient between these
two systems was resulting in gusty northwest winds. Regional radar
shows an area of light rain migrating southward through WI into
far north IL, as embedded shortwaves in deep upper trough over the
upper Mississippi Valley rotate through and interact with
moisture wrapping back down the western flank of the low pressure.

&&

Short term...(today and tonight)
issued at 320 am CDT Tue Oct 24 2017

Chilly, windy day on tap today. Gusty northwest winds draw down cold air
with 850 mb temps dropping into range of -1c to -2c today. This
coupled with clouds and light rain at times (mainly this am and
especially east) will result in unseasonably cool temps today
mostly in the 40s. Cold advection will assist in steepening the
low level lapse rates and bolstering mixing, which along with
lingering tight pressure gradient will lead to brisk/windy day.
Although not near Wind Advisory criteria at this time NW, there
is the opportunity to be near low end of criteria for a time by
late am through early afternoon in peak mixing where bufr
soundings show around 30 kts sustained and near 40 kts atop the
mixed layer. Therefore, I have left the Wind Advisory going today
for areas dbq-Cid and points northwest. As for the rain, expect an area
of mainly light rain to continue shifting south through the
region, mostly this morning and generally along and especially
east of the Mississippi River. While further west on the edge of
drying and potential for some cloud breaks mainly a few light
showers or sprinkles possible at times through midday. This
afternoon into evening will likely bring about decreasing clouds
in wake of departing upper level shortwave energy as mid level
ridging quickly builds in. This should allow temps to drop into
the 30s tonight, with some lower 30s possible in drainage or sheltered
locations where patchy frost may occur. However, a widespread frost
does not appear likely as winds should stay up just enough in
lingering pressure gradient. In addition, also likely to see an
increase in cloud cover late tonight as elevated warm air advection ensues ahead
of next wave diving through the upper Midwest. In fact, temps may
actually level off if not rise a few degrees toward daybreak with
the clouds and developing SW winds.

Long term...(wednesday through monday)
issued at 320 am CDT Tue Oct 24 2017

Looks like seasonable and changeable weather in this time frame with
cool mid week temps dropping to colder levels, with a likely freeze
and some snow flakes late week into the weekend.

Wednesday and Thursday...flow aloft becomes northwesterly and
temperatures moderate slightly as a ridge builds over the area.
Nighttime temps will be chilly, if not a bit frosty in the northeast
Thursday morning.

Thursday night and Friday...another storm system moving north of the
region will swing a cold front through the County Warning Area ushering in the
coldest air we have seen so far this season. Lows Friday morning
will be in the 30s, nearing the freezing mark in the northwest. Some
light rain is possible across the north, but if any occurs, amounts
will be light.

Friday through Sunday...cold advection continues through the day
setting up for an advective-type freeze event across the County Warning Area
Saturday morning. Still some details to flush out with the wind and
clouds which would impact how cold we get, but it looks like the end
of the growing season for many areas this night, if not Sunday
morning. Models do generate some light precip Friday night and
Saturday, but quantitative precipitation forecast is not too impressive. Temps aloft are
sufficiently cold that we could see the first snowflakes of the
season. Sunday morning looks more like a classic radiational
cooling event, so odds of getting through the weekend without a
freeze appear low.

Monday and Tuesday...while models diverge greatly on the details, it
looks like another brief warmup Monday followed by another quick
moving cold front and reinforcing shot of cold air Tuesday.

&&

Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1140 PM CDT Mon Oct 23 2017

A slow moving upper level low will impact the terminals the next 18+
hours with cloudy to mostly cloudy skies and blustery northwest winds
of 15 to 30+ mph. Ceilings will tend to be low VFR with periods of
MVFR overnight and much of Tuesday morning with periods of light rain.
The precipitation chances are handled as tempo at Cid and from group
at the other terminals. Skies will clear late PM and overnight with
winds diminishing around to after sunset.

&&

Dvn watches/warnings/advisories...
Iowa...Wind Advisory until 6 PM CDT this evening for Benton-Buchanan-
Delaware-Dubuque-Jones-Linn.

Illinois...none.
MO...none.
&&

$$

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