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Area forecast discussion 
National Weather Service northern Indiana
624 am EST Monday Jan 26 2015

issued at 355 am EST Monday Jan 26 2015

Weak high pressure will be across the area today. Skies will be
mostly clear or partly cloudy this morning but clouds are expected
to move back in this afternoon and tonight. There is a chance for
very light snow across northeast Illinois...Indiana...and far
southwest lower Michigan this evening and tonight. Highs today
will be in the in the 20s...but areas which saw several inches of
snow may struggle to get out of the teens. Lows tonight will be in
the teens...except colder single digits in those same areas with
deeper snow.


Short term...(today and tonight)
issued at 351 am EST Monday Jan 26 2015

Clipper system which brought our snow on Sunday is quickly moving
away and will eventually become massive storm off the East Coast.
Light snow should end before daybreak over far southeast. Clouds
were decreasing across the region as drier air works in from the
north. This has allowed temperatures to fall quickly and should see some
single digits by sunrise. Winds were also decreasing but still
expect a light wind which will allow wind chills to fall to around
zero early this morning.

Generally a quiet short term period but a weak sheared wave will
drop into the western Great Lakes region later this afternoon and
tonight. Forcing weak but middle levels will saturate this afternoon.
Should see middle and high clouds increase today and lower. Model soundings
show a rather pronounced dry wedge in the lowest 6kft which will be
tough to saturate for measurable precipitation. Soundings do show some
saturation this evening and could be enough to squeeze out some very
light quantitative precipitation forecast. Dgz looks to be saturated so expect any precipitation to be in
form of light snow at this time. Have kept a low chance pop in the
far west after 21z today and just a chance for flurries central.

Fresh snowpack...deepest across the south and southeast...should
hinder temperature rises today. Have lowered maximum temperatures and went with
cooler met MOS numbers. These may still be too warm in the south
depending on how much radiational cooling occurs with clearing early
this morning. Lows tonight also tricky as cloud cover will be
increasing but winds light over fresh snowpack. Lowered temperatures across
the southeast where clouds will be thin initially. Additional
downward adjustments of several degrees may be needed if cloud cover
is lacking or arrival is delayed.


Long term...(tuesday through sunday)
issued at 351 am EST Monday Jan 26 2015

Quiet conditions will prevail on Tuesday and Wednesday. Rapid height
rises will commence as deep East Coast trough lifts and next wave
approaches. Downstream amplification from this next trough will also
develop decent shortwave ridging with associated Ava generating
strong subsidence. This leads to yet another difficult cloud
forecast with potential for boundary layer moisture to be trapped
under strong inversion and keep stratus deck in place. NAM showing
its typical boundary layer moisture bias with GFS soundings much
more optimistic. Suspect we will see some breaks in the clouds by
the afternoon but will probably take some time. Midlevel warm air advection will
also generate increasing middle and upper level clouds...especially by will hold with partly cloudy at best. Temperatures will be
near average for late January with highs near the freezing mark and
lows Tuesday night in the middle to upper teens.

Next system will impact the area Wednesday night into Thursday.
Decent midlevel dynamics noted with this system but there are
several negative factors. Remnant vorticity maximum from cutoff Baja California low will
phase with another North Pacific shortwave as they swing through the
upper Midwest. Upper jet support is noticeably absent/weak for this
event though. Bulk of the heavy lifting will have to be done by
simple cva and the two waves appear disjointed on several model runs
with some question as to how much energy will be left from old
sheared out upper low. Will be plenty of moisture drawn north with
this system as strong southwest flow advects 850mb mixing ratios of
almost 6 g/kg into the region. However...this also leads to low
level thermal profiles that are above freezing. Models still sorting
out exact track of the low and it is futile to try to predict
specifics this far out. Suffice it to say...currently expect a mix
of light rain and snow across the area late Wednesday night through
Thursday. Transitory sleet and freezing rain are also likely but
strong S/SW low level flow will prevent any meaningful ice
accumulation. Any snow accumulation is also expected to be light
though some moderate totals are possible in our far northeastern
counties if precipitation types manage to remain all snow. Return to cooler
conditions behind this system but nothing out of the Ordinary for
this time of year.

Another weak low/frontal passage possible over the weekend. GFS and
European model (ecmwf) still disagree on timing and location of potential Arctic air
intrusion early next week with European suggesting 850mb temperatures below
-20c in our area by next Monday. Newest 00z GFS is later with the
cold air arrival but does show our County Warning Area getting clipped. Will once
again stay close to consensus initialization for day7 temperatures with the
added disclaimer that large adjustments are possible in the coming


Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 621 am EST Monday Jan 26 2015

VFR conditions today with high clouds this morning. Will see a
lower deck move in this afternoon but expect ceilings to remain VFR
with a rather pronounced dry layer in the 1-4kft range. Also
expecting this dry layer to help evaporate any light snow that may
fall so kept precipitation out of tafs. Winds will be generally under 6
knots today and variable.


Iwx watches/warnings/advisories...


short term...Lashley
long term...agd

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