Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
1257 am EDT Thursday Jul 31 2014

issued at 810 PM EDT Wednesday Jul 30 2014

A series of weak disturbances rotating around an upper level low
will provide a chance of mainly afternoon showers and isolated
thunderstorms through Friday. Temperatures will begin to moderate
by the weekend.


issued at 810 PM EDT Wednesday Jul 30 2014

An area of showers persists this evening across Northeast Indiana
along weak surface trough which has been enhanced by lake breeze this
afternoon. Middle/upper level forcing with the associated short
wave...has exited well east of the area however...and this should
continue to limit coverage of showers over the next few hours.
Waning instability should limit any ts and have updated forecast
to go with mainly isolated showers across far southeast portions
of the area this evening. Additional convection has developed
across northwest Wisconsin early this evening in association with
next vorticity maximum rotating around parent upper low. With bulk of this
forcing dropping southeast into the northern/central Great
Lakes...any showers remainder of the evening and overnight should
remain to the northwest/north of the local area. Updated forecast
sent to remove evening ts and to slightly tweak probability of precipitation to account
for current trends.


Short term...(this evening through thursday)
issued at 328 PM EDT Wednesday Jul 30 2014

Widely scattered showers and storms will continue to affect much of
the area into early evening away from the Lake Shadow that has once
again worked well inland. By middle evening skies will clear with quiet
conditions returning.

Upper low will finally begin to pull away later tonight into
Thursday taking the core of the coldest air with it. That being said
another weak disturbance will still move through the region with
enough lingering moisture and cold air aloft to allow for isolated
showers and storms...mainly northeast during the afternoon hours
where instability will peak in the 500 to 1000 j/kg of surface based
cape. Highs should edge a degree or 2 warmer than today with
readings in the middle to upper 70s.


Long term...(thursday night through wednesday)
issued at 328 PM EDT Wednesday Jul 30 2014

Upper low near James Bay expected to move slowly east Thursday night...
however an upper level trough should linger across the Great Lakes/Ohio Valley
into Friday... moving slowly east over the weekend. Weak shortwaves
expected to move through the upper trough and across our County Warning Area both
Friday/Sat with weak/moderate diurnal instability resulting in a chance of thunderstorms.
Better chance looks to be Friday when a surface reflection inverted trough
slides east across the area. Weak north-NE low level flow expected in the
wake of the inverted trough Saturday as surface high pressure builds over
the upper Great Lakes. A chance of showers/thunderstorms still warranted for Saturday
as lingering low level moisture should again result in weak/moderate
diurnal instability with lake breeze boundaries meandering through
the area in the afternoon to also focus convection. Given weak steering
flow and limited moisture/instability both days... expect coverage
of showers/storms will be 30-40% at best.

Upper level trough expected to move east across Ohio Sunday shifting
better forcing/instability to east of our County Warning Area. Shortwave moving across
southern Canada early next week should push a slow moving backdoor cold front
south into our area by Tuesday. Moisture pooling along the front may
allow afternoon thunderstorms to form over the area Tuesday. Western ridge expected to
continue to flatten as next shortwave moves over top and across the plains
Wednesday. This may result in scattered thunderstorms along/north of the stalled surface
boundary... mainly over northern portions of the County Warning Area.

Temperatures expected to remain a bit below normal through Saturday... then warm
to at or slightly above normal early next week as modest upper ridging
builds into the area. These warmer temperatures should persist across southern
portions of the County Warning Area at least into Tuesday... with weak cold air advection behind
backdoor cold front probably impacting at least the north-NE portion of the
County Warning Area by Wednesday.


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1256 am EDT Thursday Jul 31 2014

Light winds/mostly clear skies allowing temperatures to potentially
drop a few degrees below xover values may promote some patchy
MVFR visible restrictions at FWA/sbn just before sunrise.
Otherwise...VFR through the period. Middle level shortwave trough
axis will pivot through the lower lakes toward daybreak...likely
spreading some middle level clouds across northern Indiana. Showers
with this feature should remain north of the terminals. Weak
diurnal destabilization may once again allow a few afternoon showers to
develop...although coverage/probability appears lower than
previous days given building middle level heights/warming aloft with
low level trough focused well north across the northern Great Lakes.
Opted to hold on to a dry forecast at FWA/sbn as a result.


Iwx watches/warnings/advisories...


short term...Fisher
long term...jt

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

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

National Weather Service Glossary of Abbreviations