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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
642 PM CDT sun Oct 4 2015

issued at 324 PM CDT sun Oct 4 2015

Low level moisture continues increasing and advecting into region
on easterly flow resulting in extensive low cloudiness. 12z dvn
radiosonde observation showed fairly deep saturation from surface to around 700 mb
beneath inversion helping to maintain the cloudiness with some
breaks noted of recent over portions of eastern Iowa. The clouds
and north/NE surface winds limiting temperatures into the middle 50s to near 60.
At the surface... large expanse of high pressure was situated from
the upper Midwest and northern Great Lakes through Ontario with
ridging into the Southern Plains. Aloft... upper level ridge axis
was shown overhead with southwesterly flow prevailing through the
plains and nosing into the upper Midwest.


Short term...(this evening through monday)
issued at 324 PM CDT sun Oct 4 2015

Siding toward more pessimistic mostly cloudy/cloudy sky tonight with low
level moisture trapped beneath strengthening inversion aided by low
to middle level warm advection. These conditions are favorable for
any breaks late PM/evening to fill back in with stratus. Have seen
some drizzle periodically in a few observation to our east within the
better low level moisture... and also had a few patches occur
over our County Warning Area early this am. May see a bit more patchy drizzle
develop overnight into early Monday am with continued low level
moisture increasing especially far eastern Iowa and northern Illinois
within weak surface convergence on western flank of inverted surface
trough. Cant rule out some patchy fog as well but believe more of an
issue for aviation than public. Clouds will limit diurnals thus
stayed near or just above warm side of guidance advertising general
range from upper 40s to lower 50s.

Monday... cloud trends with impact on highs the main challenge.
Overall scenario looks similar to today with abundant low level
moisture situated beneath inversion. However...bufr soundings show
moisture not quite as deep...inversion not as strong... and also depict
more drying in the middle levels all of which may be more conducive
for development of breaks during afternoon especially on edges of County Warning Area and
advertise most areas becoming partly sunny. With anticipation of some
partial PM sun have stayed near guidance blend with widespread 60s
for highs... but these could be +/- 2-4 degrees depending on the cloud

Long term...(monday night through sunday)
issued at 324 PM CDT sun Oct 4 2015

Main forecast concern for the long term is the wave forecast to move
through the area Wednesday through Thursday night. Rain and even
some isolated thunderstorms are possible...especially Thursday as
limited instability is forecast to build into the area.

Main change in the models for Thursday is a slightly faster GFS.
This is now the outlier in the suite of models that suggests the
best chance for rain is on Thursday afternoon. The GFS ensemble is
also slower than the operational GFS. As a result a solution more in
line with the European model (ecmwf) is expected. A quick look at the instability
and soundings does suggest that isolated thunder could be possible
with the strongest updrafts. The wave does not look that impressive
and subsequent shear would downplay any threat for severe weather
and strong storms. This system appears to mainly be a rain
producing system. Once this system moves out....the flow tries to
become northwest with cooler and drier air moving again into the area.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 641 PM CDT sun Oct 4 2015

The low cloud deck that has blanketed the region since last night
has temporarily lifted to VFR levels late this afternoon. Ceilings are
expected to return to MVFR levels of 15oo to 2500 feet above ground level this
evening...and gradually lower overnight toward morning as low
level moisture increases. This will lead to some visibility
restrictions with forecasts of 4 to 5sm in fog toward sunrise.
Also...there is a potential for ceilings to drop below IFR
levels...which is advertised in the forecasts at Cid...mli and dbq
around sunrise. Monday should see conditions gradually improving
to VFR as ceilings lift and there is high confidence that VFR
conditions will prevail by middle to late afternoon.


Dvn watches/warnings/advisories...


short term...05
long term...Gibbs

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