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Area forecast discussion 
National Weather Service northern Indiana
655 am EDT Friday Mar 27 2015

issued at 447 am EDT Friday Mar 27 2015

It will be a cold late March day today...but with little more
than flurries expected. Highs will only recover into the upper
20s to lower 30s today. Skies will become clear to partly cloudy
overnight and the winds will diminish. This will allow the
temperature to plummet into the teens.


Short term...(today and tonight)
issued at 447 am EDT Friday Mar 27 2015

Core of Arctic surface ridge across upper Midwest to settle into western
Great Lakes by 12 UTC Sat. Continued drying with precipitable water falling to around
0.10 /only 0.05 inches above record regional mins/ later today.
Dry/subsident ambient environment with low based capping
subsident inversion heights to be primary negative factors
against appreciable les response. Despite Southern Lake Michigan Lake/800 mb thermal
differentials peaking into the upper teens with lake induced convective available potential energy to
near 300 j/kg midday and lakes Huron/Eastern Lake Superior differentials to
lower 20s along with cyclonic 925-800 mb flow through western
Great Lakes...still only expect modicum of les response outside of
more focused Western Lake Michigan shoreline convergence band that will
remain west of County Warning Area. Will cover with varying areal coverage/probability
mention of non measurable flurries with Lake Michigan likely shutting
down before Lake Huron with token probabilistic mention continuing into
evening far eastern County Warning Area. Continued/deepening cold air advection to afford little thermal
recovery today. And with County Warning Area on periphery of western periphery of 925
mb thermal trough over lower Great Lakes and potnl strong decoupling
ensuing overnight have given favor to the colder spectrum side of line with prior forecasts.


Long term...(saturday through thursday)
issued at 447 am EDT Friday Mar 27 2015

Very cold conditions will be at the onset of this period Saturday
with a modifying Arctic airmass across the area. Even with plenty
of sun Saturday...highs should be 15 to 20 degrees below normal.
Favor the warmer GFS. The NAM/met has been much too cold recently
with retreating Arctic airmasses...especially with sunny to
mostly sunny skies. The next challenges are with an upper level
trough of Pacific origin that should move across the forecast area
Sunday afternoon. There were major differences between the GFS
and the NAM...with the NAM continuing to hold onto the cold air
an not mix out the lower layers. Given reasonable upper level
support and timing...have raised precipitation chances Sunday.
Precipitation types still a challenge as even the warmer GFS
showing a mix of precipitation is possible. So for this
package...placed a rain and snow mix over northern areas with
just rain south. Subsequent shifts will likely need to refine
this area.

Otherwise...for the rest of the period...the upper level pattern
should become more high zonal allowing temperatures to rise above
normal by the middle of next week. Two more upper level systems
are expected to bring a chance for mainly rain Monday night...and
then just rain Wednesday through Thursday as temperatures become


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 648 am EDT Friday Mar 27 2015

Primarily VFR met conds for a few brief periods of
upper end MVFR /above fueling and alt requirements/ next few hours
asscod with pockets of deeper lake effect moisture/convection.
Steepening surface based lapse rates midday into afternoon to allow
stronger nwrly winds to mix to surface...then quickly decouple this
evening amid favorable surface cooling conds.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory until 4 am EDT Saturday for lmz043-046.



short term...Murphy
long term...skipper

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