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fxus63 kdvn 211103 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
603 am CDT Mon Oct 21 2019

..12z aviation update...

Synopsis...
issued at 243 am CDT Mon Oct 21 2019

Strong storm system moving across the Continental U.S. This morning. A closed
500 mb low was located across Nebraska. At the surface, low pressure
was located in northwest Iowa. The radar this morning had an area of
showers with embedded thunderstorms across central Iowa. This
storm system and showers and storms are expected to drive the
weather in the short term.

&&

Short term...(today and tonight)
issued at 243 am CDT Mon Oct 21 2019

Key messages
1. Showers and isolated thunderstorms will be ongoing for the
morning commute.
2. Windy and dry conditions expected in the afternoon with
temperatures in the low 40s tonight.

Not much has changed in the timing and impacts associated with
this strong mid lat system. The only thing that has changed is
that the latest models have shifted the best quantitative precipitation forecast from the NE to
the northwest County Warning Area. This is due to the better chance for clear slot
convection and wrap around rain tonight across the area. This
morning, the radar has indicated that there may be small hail in
some of these storms and that looks like a potential threat with
these storms.

Some guidance tonight suggests that we will see Wind Advisory
level winds. Im not sold on this at the current time. The hrrr
says slam dunk on the advisory, but I think its overdone. Will
need to keep an eye on how this trends through the day. As such
have left a decision for a Wind Advisory to the day shift.

Long term...(tuesday through sunday)
issued at 243 am CDT sun Oct 21 2019

Initial concern will be with winds and potential to be near advisory
criteria Tuesday, as occluded vertically stacked low pressure system
gradually shifts north of Lake Superior toward James Bay. Lingering
tight pressure gradient and good mixing in the low levels aided by
cold advection support windy conditions on Tuesday before diminishing
Tuesday night. Momentum Transfer from forecast soundings indicate the
potential for westerly winds to be at the doorstep of advisory
criteria at 20-30 mph with gusts possibly to 40-45 mph especially
northern areas. Anticipate very light rain and perhaps drizzle in
wrap-around near to north of I-80 steadily progressing east during
the day, as the strong occluded low gradually begins to pull away and
drier air begins to work in. Pops could need to be boosted in the
morning should wrap-around slow owing to a high pop/low measurable
scenario along/N of I-80.

Models continue to show a positive tilt shortwave rotating through
the upper trough on Wednesday into Wednesday evening owing to
a chance of showers along and especially north of I-80. Precipitation
signal is greatest across our far north and especially into Minnesota/WI
where best upper jet structure and associated strong frontogenetical
response is depicted, and also favorable location residing on cool
side of weak surface low with "warmer" sector more parched heading
further south through the cwa.

Continue to dry out the latter half of the week, as model consensus
keeps next system to our south Thursday night. We look to be
governed by ridging Thursday-Friday with below normal temperatures,
and increasing likelihood of a widespread hard freeze Friday morning.

No real changes for the upcoming weekend with still considerable
uncertainty and low confidence forecast on temperatures and
precipitation chances. Canadian and European model (ecmwf) models continue depicting
a rather vigorous compact negative tilt shortwave lifting up over
the region Saturday night into Sunday accompanied by a period of rain
and tempered temperature moderation. The GFS meanwhile is much weaker
and further south along the Gulf Coast, and hence dry and warmer.
Kept with blended pops and temperatures for now given the amount of
uncertainty.

&&

Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 550 am CDT Mon Oct 21 2019

Band of showers and storms will continue exiting the terminals
over the next 1-2 hours. Additional showers and a few storms
forming back across central Iowa will lift northeast and further
develop into eastern Iowa and may impact the terminals
a bit later this morning before exiting by midday. Conditions
will drop to MVFR and IFR in the precipitation. Potential for
ducting exists on the backside of the precipitation, which may
lead to some stronger winds this morning of 25-35+ kts. A dry
slot will then move across the area by late morning and early
afternoon with a return to VFR conditions. More low clouds and
MVFR to IFR ceilings expected to work back into the terminals by
late afternoon into early evening in the wrap around on backside
of low pressure. These clouds will also be accompanied by some
very light rain or possibly drizzle. Gusty east/southeast winds 10-20+ kts
will turn westerly and strengthen this afternoon and evening with
sustained winds likely around 20+ kts and gusts over 30 kts.

&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

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