Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Chicago/Romeoville Illinois
136 am CDT Monday Sep 22 2014

135 am CDT extended period of quiet and dry weather is expected
through next weekend. We will also be experiencing a slow warming
trend with highs in the 60s today and then highs in the middle to upper
80s by late week.

Today through Tuesday...
the upper level trough is pushing east and an upper level ridge will
move over the region tonight and Tuesday. High pressure is over the
Central Plains early this morning and it will drift east over the
County Warning Area today. The gradient will weaken allowing winds to diminish this
morning and become west to southwest by this afternoon. A weak lake
breeze is possible in Cook County late this afternoon. Looking at a
beautiful sunny fall day with highs in the 60s.

Clear conditions and light winds continue tonight with lows in the
50s near the lake and in the 40s in the outlying areas.

The center of the high moves over the upper Ohio River valley
tomorrow and looking at another dry and sunny day. High temperatures will
be a bit warmer in the low 70s. The weak pressure gradient may
allow a lake breeze to form late in the afternoon so may see temperatures
stay around 70 along the lake. Otherwise light SW winds will
become S to southeast in the afternoon.


Tuesday night through Thursday...
large anti-cyclonic feature will persist...with a continued theme of
dry weather and light winds. Minimal cloud cover during the
overnight hours with light winds will allow temperatures to easily radiate
into the upper 40s/low 50s. Afternoon highs will return to near seasonal
conds generally in the low/middle 70s. Potential for a lake breeze in
the afternoon hours will bring cooler temperatures to areas adjacent to Lake

High confidence in the medium term.

Friday through Sunday...
ensembles continue the dry theme into the upcoming weekend...with
middle-level ridging prognosticated to slide overhead and amplify slightly
Fri/Sat. This will likely result in a continued moderation to afternoon
temperatures...possibly going above climatology in the upper 70s to perhaps 80
degrees south of I-80 Fri/Sat. For the second half of the weekend
ensemble suggest the middle-level ridge will begin to dissolve and drift
east...with the longwave pattern turning more southwesterly as the
trough across The Four-Corners region begins to pivot east into the
Southern Plains. At this time though guidance suggests precipitation will
remain west of the forecast area through the weekend. Given the dry
conds and minimal clouds/light winds...expect overnight lows to easily
radiate into the low/middle 50s.

High confidence in the extended forecast.




//Ord and mdw concerns...updated 06z...

* none.


//discussion...updated 06z...

High pressure will build over the region today leading to an
extended period of quiet VFR conditions. North to northwest winds
will slowly back to west by early to middle afternoon. Wind speeds
will remain light around 6 knots.

Gary will be a bit different from the rest with gusts around 20 knots
early this morning off of the lake and the only location with
cloud cover. Clouds will thin and wind speeds will diminish
through the morning. Winds at Gary will also back to the most to
SW this evening.


//Ord and mdw confidence...updated 06z...

* high confidence in all forecast elements.


//outlook for Ord/mdw for 12z Tuesday-12z Sunday...updated 00z...








135 am CDT

For the Small Craft Advisory...extended the advisory into this
afternoon for Illinois and this evening for in. Winds remain high with
gusts around 25 knots at the crib and Michigan City buoy. Therefore
expecting waves to diminish slower than previously thought.

High pressure will build over the region today and north winds will
diminish and back to west or northwest. A lake breeze is possible over Cook County
this afternoon. The high continues east and winds become south on its
backside Tuesday afternoon and evening. South winds persist into the
weekend around 10 knots or less. The southern half of the lake will have
southeast to east winds through the weekend as well.



Lot watches/warnings/advisories...
Lm...Small Craft Advisory...Illinois nearshore waters until 4 PM Monday.

Small Craft Advisory...Indiana nearshore waters until 10 PM Monday.



Visit US at http://weather.Gov/Chicago (all lowercase)

Follow US on facebook...twitter...and youtube at:

National Weather Service Glossary of Abbreviations