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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
409 am CDT sun Aug 31 2014

Short term...(today and tonight)
issued at 406 am CDT sun Aug 31 2014

Today...areas of...to patchy fog to continue through at least 14z this
morning with nature of most of it shallow or low based layer fog. But
some of it dense and will put out at least a Special Weather Statement for
early morning travel. Otherwise...low level ridge will start to migrate
eastward today while upper ridge currently bulging across the middle to
upper MS River Valley will gradually transition cyclonic south-
westerlies by middle this evening. Still signs of a lead elevated warm
air advection Wing on organizing southwesterly 850 mb mb jet of 30-40
kts across north central into northeastern Iowa this morning into early
afternoon. A few of the hires solutions suggest isolated to widely
sctrd showers may pop up across the northern County Warning Area through midday...but
with lingering upper ridging will just raise non-mentionable probability of precipitation for
now and keep the forecast dry. Otherwise a mainly sunny and warm day on
tap with mixing low level southerlies to base of 850 mb mb inversion support
highs in the middle to upper 80s across most of the local forecast area.

Tonight...digging upstream trough currently seen on water vapor imagery
across the west central rockies will look to shear across the MO river
vally this evening. Strong low level thta-east feed and building instability
up into the Lee of this process...as well as several model indicated
mesoscale convective system forcing tool suggest convection to really Blossom across the east
Central Plains up into Minnesota later this afternoon and evening...
northeastern Kansas across the western third of Iowa and toward the msp Minnesota
area. Strong southwesterly low level feed of 30-45 kts and forcing of the
middle and upper trough itself should allow for storms clusters or an
eventual mesoscale convective system/possibly linear in nature looking at strong low to middle
level shear profiles/ to propagates eastward into the dvn County Warning Area from
late evening and especially after midnight. If system is mature as
it enters the County Warning Area...there still may be a damaging wind threat even
later at night. But some other mixed signals by the 00z solutions
suggest one better forced storm cluster may move to the north of the
area along the Iowa/Minnesota border into southeastern Minnesota into WI through Monday
morning...and another complex or mesoscale convective system passing across the north half of
MO. This could lead to secondary and weakening storm clusters or
lines of storms moving across the local forecast area in between the two
hotter zones. The 00z NAM and GFS may be advertising too strong of
low level shear vertical profiles later tonight...but incoming mesoscale
wind flow trends will half to be monitored. But with the potential
and variances in model details...will keep high probability of precipitation going after
midnight and into early Monday morning spreading in from the west.
Unless we get the weakening storm line scenario...another chance for
some locally heavy rain later tonight with some areas possibly
receiving over an inch of rain by sunrise Monday. Taking into account
the possibility of rain cooled surface outflow in some areas while other
areas may get missed...lows tonight to generally vary from the middle
60s to lower 70s. ..12..



Long term...(monday through next saturday)
issued at 406 am CDT sun Aug 31 2014

Monday-Monday night... anticipate weakening thunderstorm complex moving across
County Warning Area Monday am. Shortwave trough is shown to shift from the upper Midwest
into the Great Lakes by late in the day ushering in a cold front. The
cold front or effective boundary from morning storms may serve as
a Focal Point for re-development of storms by middle to late PM. Moderate
cape (1500-2500 j/kg) and strong/high 0-6km shear (40+ kts) supportive
of organized severe storms. However... risk of severe conditional
due to uncertainty with degree of destabilization (clouds and precipitation
may limit)... weak frontal convergence... and main upper level forcing
passing north/NE of the County Warning Area. With sufficient destabilization... and
forcing aided by 300 mb 80-90+ knots jet... then would anticipate at least
scattered storms developing ahead of front/effective boundary by middle-late
PM. Forcing aligned parallel to front suggestive of fairly short-lived
supercell structures with hail and/or wind before transition to a line
with wind threat with some embedded bowing segments. Precipitable waters of 1.5-2 inches
with deep warm cloud depths suggestive of locally heavy rains possible...
but storms should be moving quickly to limit rainfall to mainly 0.5 inch
or less. Once again... the severe risk for Monday PM is conditional upon
sufficient heating/destabilization and forcing. Monday night will see main
chances for showers and storms exist across the southern County Warning Area being in
closer proximity to boundary and strengthening nocturnal low level jet.
Lows Monday night coolest northwest County Warning Area (55-60f) to warmest far south/southeast
(mid 60s).

Tuesday-Tuesday night... trending drier with front or effective boundary south of
the County Warning Area and weak surface high traversing the region. Highs mainly
around 80 or lower 80s... while lows Tuesday night in the upper 50s to lower 60s.

Wed-Sat... shower and storm chances will return during the period. Main
challenge will be timing these rain chances due to continued medium
range model run to run variances with location/movement of front and timing
of upper level disturbances. Overall...would appear targeting Wednesday night-Thursday
for first rain chances with front lifting back northward through the region.
Then...may see period of capping and diminished chances by late Thursday PM
into early Friday with boundary to our north and amplifying upper level ridge
over the central US. Late week then would appear to bring next chance
of precipitation with front returning back south as cold front as upper level trough
shifts across the upper Midwest into the Great Lakes. Temperatures to fluctuate
a bit with a day or two of above normal readings middle-late week before
trending near to below normal next weekend with cooler Canadian high settling
in.

&&

Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1137 PM CDT Sat Aug 30 2014

Expect MVFR visibilities developing overnight with a clearing sky and
light wind. Periods of LIFR/IFR visibilities and/or ceilings
anticipated from 09z-13z. Late in the period...a thunderstorm
complex will likely be approaching eastern Iowa. Will introduce a
thunderstorms in the vicinity group at 04z Sunday night...and kept rest of taf sites dry
through 06z.

&&

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

$$

Short term...12
long term...05
aviation...rp Kinney

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