Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
737 am CDT Wednesday Apr 23 2014

issued at 734 am CDT Wednesday Apr 23 2014

At 7 am we let the frost advisory expire. A product was not sent
out...but none the less this is what occurred. Otherwise...a large
area of showers has already developed over the Missouri
Valley...and should continue to move east. Thus far it seems to
fit the idea of widespread scattered showers...with many spots
seeing a shower...but lesser seeing actual measurable showers.



issued at 300 am CDT Wednesday Apr 23 2014

What started out as a quiet...clear and cold now
transitioning into a mostly cloudy early morning as middle and high
clouds stream into the County Warning Area from the west. This cloudiness is on the
nose of the lead warm air advection near the edge of the upper ridge axis. To the
west of the upper Kansas and Nebraska...there have been
elevated showers and even some thunderstorms taking place early
today. This process will make a move toward our County Warning Area this morning.
Temperatures range early today from the middle 30s east to the upper
40s west. For changes are being made to the frost advisory
which is in effect for our eastern County Warning Area through 12z.


Short term...(today and tonight)
issued at 300 am CDT Wednesday Apr 23 2014

With little will not be as nice as yesterday. Clouds
should continue to increase and thicken during the morning...leading
to much less heating and highs only in the middle 50s to lower 60s in
most locations. An east wind will be strongest in the west where the
surface pressure gradient is much tighter...generally 15 to 20 miles per hour. The
eastern 1/2 should be more around 10 to 15 miles per hour east. All locations
should see stronger east winds the 15 to 25 miles per hour range.

Confidence on measurable rain from elevated showers remains lower
than normal today. I do believe most locations will see a shower at
some point...but with such dry air advecting in at low levels...we
will need to see vigorous middle level showers to be able to measure.
This potential seems highest in the north 1/2 though a shower could
measure anywhere given the robust warm air advection aloft. This same process
continues tonight...with a gradual shift northward of any warm air advection band.
The main upper forcing associated with the surface low/cold front
will near our western County Warning Area after midnight...with the main show still
over central Iowa overnight we will likely widespread coverage
toward late night west...but not anything too heavy. I am thinking
overnight quantitative precipitation forecast should be generally 0.25 or less and confined to the
western 1/3. Temperatures tonight will be cool with the light precipitation
and dry low levels wetbulb temperatures in the lower 40s seem likely in the
north...with the drier and cloudy south bottoming out near 50.

Long term...(thursday through tuesday)
issued at 300 am CDT Wednesday Apr 23 2014

On Thursday the main energy moves the area followed by the cold
front during the afternoon. Rain should be over the western areas at
sunrise and will overspread the area during the day. The most
widespread coverage of precipitation should be from middle morning
through middle afternoon with rain slowly ending from the west by late

Rain will continue to end from west to east Thursday evening as the
cold front moves east of the area. After midnight dry conditions are
expected with clearing skies.

Dry conditions will be seen Friday and Friday night as high pressure
builds into the Midwest. Temperatures should average above normal.

Saturday on...
the scenario of an anomalously deep upper low developing over the
eastern Continental U.S. Is the only thing the global models agree on. There
continues to be disagreements on when and where the upper low forms.
These disagreements play considerably into how the daily sensible
weather evolves from Saturday through Tuesday.

The current model consensus has dry conditions for Saturday with
temperatures slightly below normal.

Starting Saturday night and continuing through Tuesday the model
consensus has chance probability of precipitation with the exception of Sunday night where
the model consensus has likely probability of precipitation. Temperatures through the period
should average below normal.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 626 am CDT Wednesday Apr 23 2014

Middle and high clouds will stream over the area today...along with
occasional showers from very high based clouds. Thus...while brief
wetting rains are possible...conditions should remain VFR through
late tonight. Winds will be easterly at 10 to 20 kts today and
tonight...with stronger winds of 15 to 25 kts possible in Iowa
tonight. A low pressure and cold front will move in late tonight
and Thursday providing a more widespread threat for showers and
thunderstorms. This should begin impacting eastern Iowa around 09z
tonight...and slowly move over all of the region through Thursday
evening. This will likely be associate with MVFR conditions in rain.


Dvn watches/warnings/advisories...


short term...Ervin
long term...08