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fxus63 kdvn 222154 
afddvn

Area forecast discussion
National Weather Service Quad Cities Iowa Illinois
354 PM CST Wed Feb 22 2017

Synopsis...
issued at 220 PM CST Wed Feb 22 2017

Record warm spell continued today with all climate sites breaking
daily records and some even all-time February highs. Highest temps
today occurred from eastern Kansas into our western cwa, where there
were no clouds and dewpoints in the lower to middle 40s. Nice
dewpoint gradient over the dvn County Warning Area was evident on msas analysis
stretching from eastern Texas all the way north into our western
counties. Deep mixing depths up to 900 mb also contributed to the
warmth. Storm system to impact the region Thursday afternoon
through Friday, was tracking into Nevada as of 20z this afternoon.

&&

Short term...(this evening through thursday)
issued at 220 PM CST Wed Feb 22 2017

Forecast focus in the near term is on precipitation timing
Thursday afternoon.

A weak cold front will push east overnight tonight and then stall
over central Missouri and southern Illinois. After looking at low
level moisture progs and surface wind fields, have added the
mention of patchy fog for areas east of MS river early Thursday. Do
not anticipate anything becoming dense or lasting that long like
this morning. Lows Thursday am will be in the upper 30s to lower
40s.

Latest model solutions have the stalled front a tad further south
than in previous runs, before it begins to lift north as a warm
front late Thursday. Strong lift signal from latest model runs
supports an area of overrunning rain to develop north of the warm
front Thursday afternoon, from northern MO into the central
portions of the County Warning Area by 00z Friday. Quantitative precipitation forecast amounts will be rather
light and less than a tenth of an inch. Clouds to increase
throughout the day Thursday with easterly winds. However,
temperatures will still reach the lower 50s north of Highway 30,
to the lower 60s in northeast Missouri and west central Illinois.
This is still above normal for late February.

Long term...(thursday night through wednesday)
issued at 220 PM CST Wed Feb 22 2017

Thursday night...

Showers and thunderstorms are forecast to develop mostly after
sunset in response to increasing warm air advection and convergence
along elevated 850-700mb warm front/jet nose. Presence of steep mid-
level lapse rates near 7 c/km, MUCAPE exceeding 500 j/kg, and
effective deep layer shear around 50 kts, warrant a low risk for
hail up quarter size. Expecting severe hail reports to be isolated
with pea to dime size more prevalent. The Storm Prediction Center
has outlooked the SW half of the County Warning Area with a marginal risk for severe
thunderstorms.

Friday...

Strong Spring-like storm system will impact portions of the upper
Midwest. There is uncertainty regarding the exact track of the sfc
low which will have implications on sensible weather across the dvn
County Warning Area. Outside of the NAM, other models have trended southeastward.
The European model (ecmwf)/Canadian/GFS ensemble mean have a more rapidly occluding
low struggling to push north of the Quad Cities. Therefore, this is
a much colder scenario for highs across the northwest third of the County Warning Area.
Adjusted highs down slightly from the superblend in this area, but
raised them in my southeast. Looks like a very impressive northwest to southeast temp
gradient across east Iowa/northwest Illinois from 40s (maybe colder) to
mid/upper 60s.

The dry slot should push most of the steady precip to the north of
the region by late morning, although it could linger across my far
northwest through the day with a risk for some sleet or snow late Thursday
night through Friday.

Thunderstorm potential...

There is a marginal risk for severe thunderstorms from the late
morning into the early afternoon mainly east of the Mississippi
River along and ahead of the cold front. Conceptually, this is a
high-shear Low-Cape setup. Since confidence is low on where these
storms form - they may develop just to the east of the County Warning Area - do not
want to get too much into the details yet. Stay tuned to future
forecasts for updates.

Friday night through Saturday night...

Accumulating snow possible:

Strong 850mb cold air advection wraps in with deformation zone
precipitation bringing a good chance for light snow. Even though
temps have been anomalously mild the past 1-2 weeks, sfc temps are
forecast to fall into the 20s Friday night into Saturday morning -
cold enough to accumulate some of the snow that falls. A half inch
to around 2 inches are possible, highest north of Highway 30. Main
concerns are stretches of icy/slippery roads and reduced visibilties
with wind gust up to 30-35 mph.

Sunday through wednesday:

Chance for light rain and snow Sunday into Sunday night. Pops are
low between 20-40%, highest south of I-80. Then temps are forecast
to warm ahead of the next strong low emerging in the plains. Could
have another round of showers and thunderstorms, and possibly a
changeover to snow on the backside of the low into Wednesday.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 220 PM CST Wed Feb 22 2017

VFR conditions to be found through most of taf cycle at all sites.
Occasional gusts over 20 kts can be expected this afternoon at
Cid/dbq/mli. A cold front will switch winds to the northwest by
the middle of the evening, then turn to the northeast after
midnight. Guidance does show some Post frontal MVFR clouds trying
to drop south early Thursday and have included a sct030 deck at
dbq/Cid.

&&

Hydrology...
issued at 352 PM CST Wed Feb 22 2017

Area river sites on the Iowa and Cedar rivers are forecast to rise
into minor flood stage by this weekend into early next week.
However, confidence on this occurring is low because the river level
forecasts are contingent on widespread 0.75 to 1.00 inches of rain
falling from Thursday night through Friday. For the aforementioned
reason, and since the risk for minor flooding is beyond 48 hrs from
now, decided to hold off on issuing river flood watches at this
time. Uttech

&&

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

$$

Synopsis...gross

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