Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
1219 PM CDT Friday Mar 27 2015

Synopsis...
issued at 259 am CDT Friday Mar 27 2015

Surface analysis shows high pressure centered over the Red River
valley of the north this morning where temperatures were in the middle
teens with light northerly winds. A cloud deck between 4 to 6 kft
stretched between from central Iowa northeastward to southwestern
Ontario. Underneath this cloud layer temperatures remained in the
upper 20s to lower 30s.

&&

Short term...(today and tonight)
issued at 259 am CDT Friday Mar 27 2015

The main forecast concerns this period will be the cloud cover
across the region and its effects on temperature today. Models were
in good overall agreement.

Positive pna pattern across North America today with a persistent
ridge across the western US and a trough across the east. A strong
baroclinic zone stretches from southeastern Alberta southeastward to
the Kansas...Oklahoma border before curving eastward.

Currently clouds across the region have helped to keep temperatures
warm overnight as they have been slow to shift southward with time.
Satellite trends and observations indicate a slow clearing from
north to south with clouds exiting northeast Missouri and west
central Illinois after sunrise this morning and am not concerned
with clouds keeping temperatures cooler than forecast.

High pressure will move southeastward through the day on Friday with
a relaxing pressure gradient and weakening winds. Models also
indicate drier air moving into the region. Expecting a pleasant but
unseasonably cold day. Model 850 temperatures of -12 to -14*c are
forecast by 18 UTC which with mixing to roughly that level today
yields temperatures from the lower 30s north to the middle 40s south.

Northwest flow aloft across the plains will lead to another
approaching clipper for Friday night into Saturday morning. Models
indicate that the better moisture and lift will remain to the south
and west of eastern Iowa...northwest Illinois and far northeast
Missouri.

Long term...(saturday through thursday)
issued at 259 am CDT Friday Mar 27 2015

A more active weather pattern and milder temperatures are the
highlights of the long term forecast period.

On Saturday...modest warm air advection with light return flow will boost highs
into the upper 30s/middle 40s. The first in a series of short wave
troughs will impact the forecast area as early as Saturday night
with more widespread precipitation on Sunday. Model timing is
generally faster with the 27/00z runs...the exception being the
European model (ecmwf) which is a slow outlier. Likely probability of precipitation still on target for
Sunday. Forecast soundings indicate some potential for a wintry
mix of rain/snow/sleet late Saturday into Sunday morning before a
change over to all rain. With increasing southerly winds and
rising temperatures likely after midnight Saturday night...freezing rain
is not expected to be much of an impact at this point.
However...confidence is specific precipitation types is not all that high
this far out and have gone with a general rain/snow mix in the
forecast grids...to be refined with later forecasts. Expect
another decent bump in temperatures on Sunday...with highs in the middle 40s
northeast to upper 50s southwest.

Looking ahead...expect quasi-zonal flow through the rest of the
forecast period with mild Pacific air boosting temperatures into
the 60s to near 70 degrees by Wednesday. Another weak wave may
glance the far northeast with some light rain Monday night.
Otherwise...the next favored window for showers and thunderstorms
will be on Wednesday...potentially impacting the entire forecast area.

&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1217 PM CDT Friday Mar 27 2015

VFR conditions will be seen through 00z/29 as two separate high
pressures move through the Midwest. A weak storm system will drop
southeast through the plains after 00z/28 resulting in only an
increase of high and some middle level clouds.

&&

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

$$

Synopsis...cousins
short term...cousins
long term...rp Kinney
aviation...08

National Weather Service Glossary of Abbreviations