Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
749 PM EDT Thursday Oct 8 2015

issued at 130 PM EDT Thursday Oct 8 2015

A cold front will move across the region tonight bringing a chance
of rain showers and a slight chance of a thunderstorm. Cooler
temperatures are then expected for Friday into Saturday but warmer
weather will briefly return Sunday into Monday. Low temperatures
tonight will drop into the low to middle 50s and highs on Friday will
only climb into the lower to middle 60s with breezy northwest


Short term...(this evening through friday)
issued at 305 PM EDT Thursday Oct 8 2015

Short wave trough expected to cross the region during the short
term period. This will drive a cold front across the local area
tonight. Middle level forcing not great but sufficient combined with
low level convergence near front to support chance to likely
probability of precipitation...especially north. Hires guidance in good agreement with
band of rain developing along and just ahead of front. This should
sweep across central and northern locations. With questions
remaining on coverage and precipitation expected to be light and possibly
decaying with southern and eastern extent...opted to keep probability of precipitation in
the chance to likely range until development is seen on radar.

Precipitation quickly ends Post frontal with winds becoming northwest. Low
level cold air advection and residual moisture should lead to a
broken to overcast low cloud deck late tonight into middle day
Thursday. Slow clearing from northwest expected later in the
afternoon but more rapid drying arrives early evening. It will turn
cooler but still seasonable with highs Friday ranging from upper 50s
near Lake Shore to middle 60s far southeast.


Long term...(friday night through thursday)
issued at 305 PM EDT Thursday Oct 8 2015

If you do not like the temperatures you are seeing now...just
wait a few days as the roller coaster ride continues through most
of the forecast period.

The region will be at the bottom of the coaster at the start of the
period as high pressure will be moving across late Friday night into
Saturday. The overall flow pattern will be more progressive allowing
the colder air to quickly shift east and allow a return flow ahead
of the next system. As a result...we will climb back up the track to
above normal for Sunday and Monday. Next chance for showers will
arrive with cold front and yet again another drop in temperatures to
near or below normal. Return of moisture will be somewhat more
scarce as the front arrives Monday...but timing of the day and
decent dynamics does warrant chance probability of precipitation. Best chances likely in the
west late am into middle afternoon and then early afternoon to maybe
early evening east...but being that far out will just leave
broadbrushed chance probability of precipitation. Flow off the lake and secondary wave may stir
up some additional clouds and make some lake enhanced
sprinkles...but not worthy of any mention beyond here for Monday

As a large cutoff low takes shape over Hudson Bay a semi zonal flow
will set up across the northern US with a series of weak waves
mainly north of the area. Will continue with dry forecast.


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 729 PM EDT Thursday Oct 8 2015

Broken line of showers and a few ts over northern Illinois ahead of a cold front
extending from northern WI through eastern Iowa should impact the terminals
overnight as the front moves east. Given rather dry low levels...
expect the rain showers will contain MVFR conditions at worst. Ts expected
to remain isolated with just weak elevated instability as the
convection moves across northern Indiana so left mention out of tafs.
Band of MVFR ceilings in cold air advection regime behind the cold front across northern WI/Minnesota
should move across northern Indiana late tonight and Friday morning.
Drier air moving in during the afternoon should raise ceilings to VFR and may
cause clouds to scattered out. Modest SW winds will increase a bit from
the northwest behind cold front.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory from 5 am Friday to 2 am EDT Saturday for



short term...Lashley
long term...Fisher

Visit US at www.Weather.Gov/iwx (all lower case)

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

National Weather Service Glossary of Abbreviations