Area forecast discussion
National Weather Service quadrant cities Iowa Illinois
1217 PM CDT Tuesday may 21 2013
Synopsis...
issued at 255 am CDT Tuesday may 21 2013
Analysis shows large surface and upper low system pin Wheeling across
the eastern Dakotas moving slowly southeast. This puts forecast area
in dry slot which will continue for roughly the next 12-15 hours.
Diffuse cool front will move across the area this evening bringing
clouds and cooler temperatures. Verification at 2 am shows cool
air on back side of system on the stronger side of all solutions.
Upstream energy supports below normal temperatures and active
westerly flow the next 5 plus days and possibly longer.
&&
Short term...(today and tonight)
issued at 255 am CDT Tuesday may 21 2013
Today...southwest winds will increase to 15 to 25 miles per hour by middle day
with partly to mostly sunny skies. This will result in a day similar
to yesterday with lowering dewpoints and highs a degree or two
lower today for a nice and comfortable late Spring day. Have kept
isolated shower or thunderstorm locations mainly east of the
Mississippi River middle to late PM but later shifts may be able to
remove due to mixing of lower dewpoints and lack of a forcing
focus. Highs should range from around 73-74 far northwest to 80-82 southeast
sections.
Tonight...clouds to increase with wave from Southern Plains to impact
locations along and east of the Mississippi toward daybreak. Upped
probability of precipitation to likely far east with showers and more probably just light rain.
The mostly slight chance evening probability of precipitation of thunder may be able to changed
to just showers with lack of focus and instability by later shifts.
Nichols
Long term...(wednesday through monday)
issued at 255 am CDT Tuesday may 21 2013
The models show a respectable surface wave moving through the area
on Wednesday bringing a threat of rain to the area. The possibility
of thunderstorms is questionable given how cool the airmass is and
what is suggested in the forecast soundings. However...have elected to
keep a mention of isolated thunderstorms over roughly the eastern
half of the County warning forecast area Wednesday afternoon where slightly stronger lift is
indicated by the models.
Wednesday night/Thursday morning showers will persist across the area as
the surface low slowly moves east into Indiana. By Thursday afternoon
most of the area should be dry as the better moisture and forcing
moves east of the area. Temperatures on Thursday will be below
normal.
Thursday night will be chilly and dry as a very cool Canadian
airmass builds into the area.
Friday on...
the model consensus has cool and dry conditions across the area on
Friday with Canadian high pressure over the Great Lakes.
The model consensus has schc/chance probability of precipitation Friday night and then chance probability of precipitation
from Saturday through Monday. The models generally agree on
developing return flow Friday night but the strength of the Canadian
high combined with flow off Lake Michigan will help keep an
effective boundary across the area. Disturbances arriving from the
plains will interact with this boundary and bring a near daily
threat of rain to the area from Saturday through Monday.
The flow off Lake Michigan will also result in temperatures well
below normal from Friday through Sunday.
08
&&
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1208 PM CDT Tuesday may 21 2013
Stalled low pressure over Minnesota will will drop southeast through
eastern Iowa and weaken late tonight and Wednesday morning.
Widespread cumulus based around 35hnd feet this afternoon will
dissipate with loss of heating by early this evening. An area of
showers will lift northeast brushing locations near and east of
the Mississippi River late tonight and Wednesday. At this time it
appears flight conditions will remain VFR in the showers except at
kdbq where ceilings could drop below 3kft. Further west...an area of
MVFR clouds and scattered rain showers will accompany the weakening low
pressure as it moves through the region. MVFR ceilings should reach kcid
after 12z Wednesday.
Dlf
&&
Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&
$$
Synopsis...Nichols
short term...Nichols
long term...08
aviation...dlf
