Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
631 am CDT Tuesday Mar 31 2015

issued at 626 am CDT Tuesday Mar 31 2015

Update to add clouds/patchy fog across the extreme northeast early
this morning. Impact should be limited to Jo Daviess...Stephenson...and
Carroll counties through 14z-15z.


issued at 306 am CDT Tuesday Mar 31 2015

At 3 am CDT...surface low pressure had moved into the Chicago area
with a trailing trough back into northeast Iowa. Early morning
temperatures ranged from the upper 40 to middle 50s. Clouds and
patchy dense fog had advanced into southern Wisconsin...with a
mostly clear sky across the rest of the region.


Short term...(today and tonight)
issued at 306 am CDT Tuesday Mar 31 2015

The main forecast issue in the short term period is temperatures.

In the near term...there is some potential for some low stratus/fog
to clip the far northeast counties toward daybreak. Conflicting relative humidity
forecasts among high-res models leads to low confidence of any impacts
in the forecast area...but will continue to monitor for possible
inclusion in later updates. will not be as windy as yesterday...and afternoon
relative humidity values will be a bit higher. The grassland fire danger index is
forecast to be in the high category over most of the area this
afternoon...compared to the very high category on Monday. A
slightly cooler airmass will be in place today...and have kept
afternoon highs about 2-3 degrees below Monday for most locations.
Highs will be in the 60s to around 70 southwest. For tonight...light
and variable winds will transition to light southeasterly with
lows generally 35 to 45...about 5 degrees above seasonal normals.

Long term...(wednesday through monday)
issued at 306 am CDT Tuesday Mar 31 2015

Main forecast problem of the long term are the chance for
thunderstorms on Wednesday evening into Thursday. The
timing...intensity and total amount of quantitative precipitation forecast are the main forecast

At the beginning of the period an upper level ridge will be advecting
through the area....helping to raise our temperatures into the middle
and upper 70s. A few sites may break the 80 degree mark on
Wednesday. A vorticity maximum will be moving through the High Plains on the
heels of the ridge and will help to bring Gulf moisture into the middle
Mississippi River valley. Timing of the attendant cold front and
subsequent thunderstorms will drive the event.

Storm Prediction Center and guidance suggest that strong to severe thunderstorms are
possible to our west across western Iowa and eastern NE. As the front
moves closer to the area these storms will be moving towards our
area. These they approach our area...will be
encountering a less favorable thermodynamic environment while at the
same time experiencing a more favorable low level shear
environment. Believe that the storms will weaken and become
elevated as they March east. Storm Prediction Center has a marginal risk for severe
weather across our MO and Iowa counties. This seems reasonable with
the loss of daytime heating. Storms will likely be waning in
intensity and there could be some gusty winds as they move into the

Like previous runs...the GFS has a faster moving cold front where
the European model (ecmwf) is slower. Faster moving front means a better chance for
strong storms in our area. Slower moving means that the storms will
be more elevated in nature.

All of the guidance produces what appears to be showers and possibly
some thunderstorms way to our south. I do have a concern that some
of the moisture from the Gulf could be cut off by these
thunderstorms. If this is possible that total rainfall
and chance for thunderstorms will be lower than what is currently
forecast....especially during the day. Overnight the models
decrease the coverage of these storms and a low level jet kicks in. This
would help to supply moisture to our rain and storms overnight.
However my gut feeling is that if the storms do form to our south
during the day and then a low level jet develops...the storms across the lower
Mississippi River valley would last longer than models depict. This
will be an important aspect to keep an eye on.

There are many different factors in this be sure to
pay attention to future forecasts...especially if the GFS and other
models can agree on the timing of the front.

The cold front then stalls to our south and leads to rain through
day Friday. It looks like between the system on Wednesday and the
rain Thursday into Friday...we could see a decent rainfall for the
area. Cooler air returns for Friday before a ridge moves into the
area. Warming US up for the weekend. A few waves in the flow lead
to some showers this weekend.

Models diverge on solutions towards the end of the period with the
possibility of some rain and even thunder at the end of the long term.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 626 am CDT Tuesday Mar 31 2015

VFR conditions to continue as early morning low clouds/patchy fog
expected to just miss kdbq. Expect an increasing northwest wind by late
morning...sustained around 12 kts with higher gusts...then
becoming light this evening.


Dvn watches/warnings/advisories...


Update...rp Kinney
synopsis...rp Kinney
short term...rp Kinney
long term...Gibbs
aviation...rp Kinney

National Weather Service Glossary of Abbreviations