Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Chicago/Romeoville Illinois
819 PM CST Tuesday Mar 3 2015

818 PM CST

No major changes to the going forecast this evening. Cold front
has cleared the area and colder air is filtering into the area on
west to northwest winds. The rate of cooling will increase into
the early overnight and have made little if any adjustment to
expected lows by daybreak. Low clouds have temporarily scattered
in some areas but will fill back in through the rest of the
evening before eroding from the northwest later tonight and
Wednesday morning. Middle cloud cover will take over in its place so
any clearing would likely be brief and spotty.



Short term...
247 PM CST

Through Thursday...

Somewhat baggy cold front will move across the region this evening
and usher in progressively colder air mass through the night. Ahead
of the into the early-middle evening anticipate low stratus hanging
around and likely resulting in nearly steady temperatures and have gone a
bit above hourly guidance temperatures hanging onto 30s into the early
evening over most of the County Warning Area before bottom drops out late tonight.
Some partial clearing is expected overnight but some middle-high clouds
will move in as not currently expecting skies to go clear.

A couple days of unseasonably cold weather look to be on tap
Wednesday and Thursday. Wednesday night has potential to give
chicago's record low a run for its Money...though guidance suggests
middle-high level cloudiness could be rather extensive for much of the
night and winds staying up a bit. Both of these factors could keep
temperatures from realizing their full frigid potential...though any late
night clearing could allow for last minute drops in temperatures. Arctic
high will be near by Thursday with heart of the Arctic air mass
overhead to start the day...suggesting that highs could threaten
record low maximum temperatures. Full sunshine Thursday with lower albedo in
Chicago and rfd metropolitan areas should allow temperatures to moderate a bit
above guidance and have trended highs ever so slightly upward.



Long term...
247 PM CST

Thursday night through Tuesday...

Thursday night could be one of those nights that see temperatures
crash during the evening hours given clear skies and proximity of
the high. High does scoot off to the east overnight and southerly
winds look to develop after midnight which should allow temperatures to
level off and then begin to slowly rise prior to sunrise and did
reflect this trend in the hourly temperature grids.

Friday into next week look to be fairly quiet period with a trend to
normal and then potentially even above normal temperatures by early next
week. Strong March sun and temperatures warming above freezing this weekend
during the daytime should begin the process of chipping away at the
deep snow pack/Glacier that has blanketed the region since the early
February blizzard. Medium range guidance continues to suggest an
extended period of above average temperatures heading into the
middle of the month...the quicker the snow pack melts the warmer
temperatures could potentially get as a mean ridge is prognosticated to develop of
the nation's middle section.




We could come close to a couple records with this next cold spell.
The ones with stars (*) are most vulnerable.

Wednesday 3/4 Thursday 3/5

Record low-11 (2002)-11 (2002)
record low maximum 14 (2002)* 17 (1960)*

record low-12 (1873) 0 (1978)*
record low maximum 17 (1890) 12 (1901)



//Ord and mdw concerns...updated 00z...

* MVFR ceilings expected through the night becoming VFR Wednesday morning.

* Occasional gusts to 20 knots this evening.

* Northwest winds gusting to 25 knots Wednesday.


//discussion...updated 00z...

The cold front has moved into north central Illinois...and has passed
through rfd. Expecting occasional gusts to 20 knots ahead of and along the
front...but then gusts dissipate behind the front. MVFR ceilings extend
back through the Dakotas so very confident in MVFR ceilings through
the night. Expecting ceilings to improve to VFR tomorrow morning as
drier air works its way into the region. Northwest winds will begin
gusting to 20 knots by middle morning and then to 25 knots in the
afternoon. Gusts look rather diurnal and they dissipate in the


//Ord and mdw confidence...updated 00z...

* medium-high confidence in when ceilings improve to VFR.

* High confidence in all other forecast elements.


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

Thursday through Friday...VFR.

Saturday...MVFR ceilings possible.

Sunday...schc rain or snow overnight...MVFR ceilings possible.

Monday...MVFR ceilings possible in the morning.




230 PM...low pressure over the northern lakes will merge with
deeper low pressure over northern Ontario tonight and then move
into Quebec Wednesday morning. Winds will be shifting westerly
over the next few hours and then more northwest across the
southern part of the lake overnight. The gradient will remain
tight as high pressure builds across the northern and Central
Plains Wednesday and Wednesday night and combined with returning
cold air...winds to 30kt looks reasonable. As the high moves east
across the southern lakes and Ohio Valley Thursday night into
Friday...the gradient will tighten across the western lakes with
southwest winds increasing back to 30kt with some potential for
low end gales. These winds will gradually diminish Friday night as
the gradient begins to weaken. Cms


Lot watches/warnings/advisories...
Lm...Small Craft Advisory...nearshore waters
until 6 PM Wednesday.



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

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

National Weather Service Glossary of Abbreviations