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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
345 am CDT Friday Oct 24 2014

issued at 343 am CDT Friday Oct 24 2014

Latest surface analysis was indicating ridge lobe overhead...while a surface
trough and some cyclonic flow was organizing upstream from southeastern
South the OK Panhandle. Much of the County Warning Area socked in with dense fog...
although the stratocu deck across northern Illinois helping keep the far
eastern County Warning Area in good visibility. Aloft...water vapor loop was indicating
a lead vorticity lobe over eastern South Dakota into central Nebraska...while a more
vigorous upper wave was noted further upstream to the west over


Short term...(today and tonight)
issued at 343 am CDT Friday Oct 24 2014

Today...will let ongoing fog advisory ride for now and not expand
further to the east across the rest of the County Warning Area...but will watch
it/trends east of the MS river through sunrise. After that...
challenging forecast today with regards to cloud cover...precipitation and
effect on temperatures/warm up potential. Looking at latest suite of forecast
soundings...will side more pessimistic with respect to cloud cover
today. Low stratocu and fog decks probably to get trapped under
building warm air advection inversion further aloft as the day
progresses. Higher clouds spilling in from the west off upstream
waves also will hinder low cloud deck break up. Thus will make most
of the County Warning Area mostly cloudy today...although the southwestern third may
go partly sunny this afternoon behind the first passing vorticity lobe now
across SD/neb. Lift off that wave coming across the area this morning
probably enough to wring out drizzle...but low level moisture/cloud depth
at question to allow for this very light precipitation to occur. It may get
close...but for now will leave out drizzle mention and just stress
the fog through middle morning. Will knock down highs some more...low
to middle 60s for the northeastern two thirds and middle to upper 60s in
the southwestern third where expect some afternoon sunshine or timely
breaks in cloud cover. South winds expected to increase ahead of
incoming surface trough this afternoon too to help the warming cause. If
clouds/fog remain stubborn...these temperatures across many areas will still
be too warm and some areas may not get out of the 50s. Attention then
turns to the next round of lift coming this afternoon to the Lee of
the Wyoming vorticity maximum. Moisture forecasts suggest a Wing of low level deepening
moisture layer up above 850 mb mb ahead of this wave...and combined with
the lift off this second feature...probably enough to produce some
spotty areas of light rain from west to east mainly along and north
of i80 this afternoon and into early evening. Will go with 20 probability of precipitation to
cover the low probability of measuring...but a few areas in the north
may get at least a hundredth.

Tonight...will walk out any lingering light rain or drizzle out of
the northeastern County Warning Area by middle evening as the lift scoots to the east
with passing vorticity maximum. Winds to veer light westerly after trough
passage...but signals of long enough periods of light winds and some
convergence around the trough axis itself may Foster more fog development
by early evening after sunset especially along an north of i80.
May be another round of locally dense fog for a period while the
surface winds stay light or decoupled. For now will go with areas of
fog through midnight...but then do expect some increase in west to
northwest surface winds into early Sat morning to help mix out the fog
if it does form. Skies will try to clear from west to east
overnight...and if surface winds do not increase after midnight like
expected...fog may become worse/expand after midnight and into
early Sat morning. Lingering higher dpt pool and boundary layer
moisture supports lows in the upper 40s to low/middle 50s for much of
the forecast area. ..12..

Long term...(saturday through next thursday)
issued at 343 am CDT Friday Oct 24 2014

Seasonably mild with chances for rain Monday...turning cooler by
late week.

Long term forecast confidence...fair or average with precipitation
event poor as evidence suggests all solutions too progressive and
not moist enough early next week. Risk of isolated thunderstorms
are marginal and suggest may be able to removed. Temperatures most
days may still be a degree or two wider than current diurnal range.
Cooling trend late in the week suggests temperatures will need
further lowering by 1 to 2 categories.

Overview...initialization good over Continental U.S. With Pacific energy poorly
sampled impacting next disturbance early next week. Verification and
run to run variance clearly suggest hi-res European model (ecmwf) should receive
highest weight supporting higher probability of precipitation early next week with widespread
precipitation totals between a tenth to over a half inch suggested.

Saturday and Sunday...splendid late October weather with fair skies
and wide diurnal temperature ranges. Highs may be a degree or two
too low and mins a degree or two too mild for later shifts. Light
winds to make for good days for fall outside activities.

Sunday night through Monday disturbance to arrive late
Monday with warm south winds and clouds to keep lows middle to upper
50s Sunday night with isolated showers along Highway 20 corridor.
Monday...south to southwest winds of 10 to 20+ miles per hour and deep mixing
supports probably one of our last fall days well into the 70s. Local
tools support some upper 70s middle to south sections. Clouds to
increase late Monday with rain and rain showers and possibly if
everything isolated storm...mainly southeast 1/2 sections as
later shifts will be able to reassess this. Have chance probability of precipitation but
jet structure and phasing suggest likely probability of precipitation and rain totals
underdone which should be better clarified next 24 hours. Local rain
tools and techniques using hi-res European model (ecmwf) supports widespread .1 to 50+
inch to isolated .75 inch amounts. Frontal passage late to likely
create a decent low temperature gradient with timing a main issue.
Current upper 40s northwest to upper 50s adequate at this time.

Tuesday through Thursday...northwest flow to bring cooler air with fair
skies and dry conditions. Dry upper disturbance to bring colder air
by Thursday with risk for later shifts mins are 2 to 5 degrees too
mild and highs possibly up to 5 degrees too mild on Thursday. Northwest
winds on Thursday may need raising with stronger but dry cool front
with reinforcing air from Canada. Nichols


Aviation...(for the 06z tafs through 06z Friday night)
issued at 1123 PM CDT Thursday Oct 23 2014

A dense fog and very low IFR ceiling event will begin the period...and
last well into Friday morning. Confidence is low on when the
minimum fog/ceilings will lift...maybe as late as 17z Friday...but
will show some improvement beyond minimums/ 1/4sm fog vv001 after
15z. In the wake of the fog...some MVFR stratus is possible
through the day Friday...again low confidence on how this plays
out since models either don't have it at all or are hammering the
area with IFR through the entire 24 hour period now. Should status
linger...another fog event with stratus is possible Friday night.
Since is most likely in northern Iowa...I have introduced another
period of IFR weather to the dbq taf after 00z/25.


Dvn watches/warnings/advisories...
Iowa...dense fog advisory until 10 am CDT this morning for Benton-
Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry Iowa-
Muscatine-Scott-Van Buren-Washington.

Illinois...dense fog advisory until 10 am CDT this morning for Hancock-
Henderson-Jo Daviess-Mercer-Rock Island.

MO...dense fog advisory until 10 am CDT this morning for Clark-



short term...12
long term...Nichols

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