Area forecast discussion
National Weather Service Chicago/Romeoville Illinois
402 am CDT Thursday Jun 20 2013
Discussion...
321 am CDT
Forecast challenges today include T-storm chances and temperatures/heat
potential over the weekend into early next week.
Surface high continues to move east but ridge axis does extend back
into northern Illinois with easterly wind (albeit light) advecting
drier air into the area. Winds will turn more southerly today with
dewpoints creeping up...though gradient should be light enough to
allow a lake breeze to form and penetrate inland...particularly into
NE Illinois. Several of the convective allowing models are showing some
isolated weak convection firing this afternoon and while this is not
out off the question chances of this occurring and coverage of
storms if it does should be low enough to stick with a dry forecast
today.
Warm front prognosticated to develop north of the area tonight into Friday
with Bermuda high establishing itself and resulting in an extended
period of very warm/hot and humid conditions with closed upper
low/deep western Continental U.S. Trough establishing itself while lower
amplitude seasonably strong ridge sets up over the central and
eastern Continental U.S.. synoptically speaking...forecast Friday through
Tuesday is straight forward with hot/humid conditions and
thunderstorm activity/ring of fire setting up north of our County Warning Area
across the northern plains east into the upper Great Lakes.
Unfortunately...mesoscale convective system activity is difficult to predict 12 hours out
let alone 48-120 hours out which means forecast confidence is not
super high for this period. These mcs's can not only result in
effective synoptic boundary being pushed farther south but can
sometimes stray off course and propagate into the low level jet//instability
axis into the warm sector. So while the majority of the Friday
through Tuesday period should be dry and thunderstorm free...really have no
choice but to maintain small (20-30%) probability of precipitation through the period due to
potential for misbehaving mesoscale convective system activity or even possible "air mass"
afternoon storms.
Anyone of the days that remain relatively convection and convective
debris free should really heat up with highs into the lower and
possibly approaching middle 90s. Conversely storms would likely result
in muggy 80s...so either scenario should result in the first very
summery feeling weekend of the year.
Izzi
&&
Aviation...
//Ord and mdw concerns...updated 09z...
* lake breeze Thursday afternoon.
* Potential for convection along the lake breeze.
Bmd
//discussion...updated 06z...
Most of the forecast should be quiet as high pressure continues to
dominate the area. The high off to our east will continue to settle
southeast over the middle Atlantic coast with easterly winds overnight
favoring a more southerly direction Thursday. The exception will be
at Ord/mdw where a lake breeze may turn winds back to the southeast
Thursday afternoon and evening. Models indicate moderate instability
developing Thursday afternoon with little capping. There may be a
few showers or thunderstorms that develop along the lake breeze
boundary and then drift east over Lake Michigan. That said...the
convergence along the front will be somewhat weak leading to little
confidence in this scenario panning out. The potential is too low at
this time for mention in the taf.
Bmd
//Ord and mdw confidence...updated 09z...
* medium confidence in wind trends.
* Low confidence in rain showers/thunderstorms and rain Thursday afternoon.
* High confidence in remaining forecast elements.
Bmd
//outlook for Ord/mdw for 12z Friday-12z Wednesday...updated 00z...
Friday through Tuesday...periodic chances for thunderstorms and rain...else VFR.
Zebic
&&
Marine...
228 am CDT
High pressure is centered over New England but its influence still
stretches across the Great Lakes early this morning. The high will
settle southeast over the middle Atlantic coast today allowing the
gradient to increase gradually over the next 24 hours as low
pressure lifts from the plains into the Canadian prairies. This will
allow winds to freshen up...particularly Friday when the northern
portions of Lake Michigan will increase to 20 to 25 knots possibly even
30 knots. There is a good chance that a couple strong to severe
thunderstorms complexes could move across Lake Michigan Friday night
through the weekend. This will likely disrupt the wind field for a
while lending to decreased confidence in the wind forecast over the
weekend. South to southwest winds are expected to continue across
the lake through the middle of next week.
Bmd
&&
Lot watches/warnings/advisories...
Illinois...none.
In...none.
Lm...none.
&&
$$
Visit US at http://weather.Gov/Chicago (all lowercase)
Follow US on facebook...twitter...and youtube at:
www.Facebook.Com/US.Nationalweatherservice.Chicago.Gov
www.Twitter.Com/nwschicago
www.Youtube.Com/nwschicago
