Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
345 PM EDT Sat may 30 2015
issued at 434 PM EDT Sat may 30 2015
A strong cold front will move southeast across the area this
evening...spawning widespread showers and thunderstorms.
Rain...heavy at times especially this evening will continue
into Sunday morning before ending as a low pressure system moves
northeast along the front. Lows tonight will range from the upper
40s over southern Michigan to the upper 50s over central portions
of Indiana and Ohio. Highs on Sunday will be much colder with 50s
across the area.
Short term...(this evening through sunday)
issued at 343 PM EDT Sat may 30 2015
Anomalously moist airmass within warm sector of approaching potent southern
stream SW ejecting northeastward out of the MO boothill a lg concern going
forward. Near term marginal severe threat tied to sufficient warm sector
destabilization this afternoon yet tempered by poor middle level lapse rates
and shear. Thus suspect nothing more than an isolated and marginal
wind threat through sunset. However rapidly increasing ll moisture
flux/ascent seen inadv of closing/deepening middle level circ portents a
a further widening/consolidation of convn within deep warm cloud
depth of which shld be a very efficient heavy rain producer.
Otrws generally discounted the solution space that over emphasized
the middle level deformation zone across northwest in/SW Michigan as compositing outflw
along a kcmi-kdfi line shld impeded btr northward moisture entrainment through lt
evening which will cut down on potential quantitative precipitation forecast there.
Upper wave flattens and shears northeastward into New England on sun and expect
precipitation will diminish/end quickly through middle morning. However
considerable cloud cover and deep nerly follow will make for a much colder
Long term...(sunday night through saturday)
issued at 343 PM EDT Sat may 30 2015
Weakening deformation precipitation across eastern locations should exit
early Sunday evening. Lingering inversion should make for a slow
erosion of low cloud deck Sunday night however. Consensus of
guidance has trended toward a bit more robust northern stream
tracking across the Great Lakes Monday helping to slow early week
Upper flow pattern to transition to more blocking in nature as
southern latitude trough cuts off across lower MS valley while mean
upper ridging settles across the Great Lakes. This should set up a
rather uneventful pattern for local area through at least middle week.
GFS is a bit more enthusiastic with weak vorts rotating into the
Ohio Valley from this southern stream cut off...but will continue to
trend to a mainly dry forecast through Thursday with weak
signals/forcing. Will maintain low chance probability of precipitation Friday and Saturday
as a more substantial northern stream trough has a better chance of
dampening upper ridging across the Great Lakes.
As mentioned...moderating trend may be a bit slower than earlier
indications...but suspect most locations should be solidly in the
lower 80s for maximum temperatures by Thursday.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 210 PM EDT Sat may 30 2015
VFR conds to being will deterioriate quickly through this evening
ahead of potent northeastward ejecting SW out of the MO boothill. Expanding
convn from eastern Illinois into central in shld steadily bridge northward through this
afternoon in response to rapidly increasing ll warm air advection although do expect a more
subdued thunder threat in vicinity of ksbn as surface cyclone tracks well south
through central in. Otrws widespread IFR conds expected to develop through
this evening as widespread rain develops across the terminals. In
addn...winds expected to veer nerly overnight and become quite gusty in
response to deepening cyclone overhead west/surface gusts to 25kts likely
in...Flood Watch through Sunday morning for inz009-017-018-022>027-
Beach hazards statement through Sunday evening for inz003.
Michigan...Beach hazards statement through Sunday evening for miz077.
Ohio...Flood Watch through Sunday morning for ohz001-002-004-005-015-
Lm...Small Craft Advisory until 6 PM EDT Sunday for lmz043-046.
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