Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
832 PM EDT Tuesday may 26 2015
issued at 825 PM EDT Tuesday may 26 2015
Scattered showers will continue to diminish through the evening.
Expect partly to mostly cloudy skies overnight with low
temperatures in the lower to middle 60s. Another round of showers
and thunderstorms is possible Wednesday afternoon. Highs will be
in the upper 70s to lower 80s.
Short term...(this evening through wednesday)
issued at 302 PM EDT Tuesday may 26 2015
Much of prior update discussion remains valid. Break in clouds
across our eastern County Warning Area earlier today allowed for modest
destabilization with current Storm Prediction Center/rap mesoanalysis indicating
around 1000 j/kg of SBCAPE. Multiple lines of convection have
developed across Indiana/Illinois but main threat will be with the
cluster of storms over central Indiana as they move
northeast...along with any other storms that manage to develop
ahead of it. Instability is marginal but decent shear...especially
in the 0-3 km layer will present a damaging wind threat with any
clusters that manage to develop more significant updrafts. Still
think the risk for widespread/significant severe weather is low
but a few scattered storms may become severe and after coordination with
Storm Prediction Center and surrounding offices decided to go ahead and issue a watch.
It is in effect until 10 PM but will likely be able to trim/cancel
a little bit earlier than that.
Expect precipitation to exit by late evening and only minor changes to
the going forecast for tonight and tomorrow. Another round of
thunderstorms possible tomorrow afternoon in our southeast zones
but severe chances appear low given marginal instability and
Long term...(wednesday night through tuesday)
issued at 302 PM EDT Tuesday may 26 2015
Increased precipitation chances Friday into Saturday highlight the
long term period.
Little changes made from previous forecast package in the long term.
Broad East Coast riding will keep above normal temperatures across
the region through the end of the week. Sharp northern stream
shortwave will dig east/southeast across northern Ontario Friday...with
deepening surface cyclone near James Bay. This will push a cold front
southeast Friday through Saturday. With ample moisture return and
decent surface forcing...went ahead an raised probability of precipitation to likely Friday
night through Saturday. Severe chances at this time are fairly
low...with unfavorable diurnal timing with frontal passage and little upper
flow/shear despite marginal instability. Will continue to monitor
through the week for any changes.
Cooler conditions will settle into the region as aforementioned
front sinks south of the forecast area Saturday into Sunday.
Maintained consensus blend chance/slight chance probability of precipitation Saturday night
through Monday...however this will likely need to be refined further
in subsequent forecast runs. Latest 12z GFS hinting at surface front
sinking south into the Ohio River valley...with strong Canadian surface
ridge shunting southeast through the Great Lakes and ushering in a
significantly drier/more stable airmass. Moisture return/warm air advection regime
may not return to the area by Tuesday...which would make current
probability of precipitation in the Sunday through Monday timeframe way too high.
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 828 PM EDT Tuesday may 26 2015
Vfe met conds should dominate through the forecast period.
However...concern that lower stratocu and/or lower visibilities may again
develop toward daybreak across northestern in/in vicinity of kfwa underneath early
am low level moist axis...though retain optimism with conds above
fueling/alternate criteria at this time. Otherwise rising cumulus field
through the day on Wednesday with point midday/afternoon convective chances too
low for inclusion at this time across northern in. Diurnal increases in wind
speed/hiest during deepest mixing... followed by weaker/wrly
veered Post frontal flow towards end of forecast period.
Lm...Small Craft Advisory until 11 PM EDT this evening for lmz043-046.
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