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Area forecast discussion 
National Weather Service northern Indiana
811 PM EDT Monday Apr 20 2015

issued at 805 PM EDT Monday Apr 20 2015

Strong low pressure over the northern Great Lakes will lift
northward into Canada overnight and to James Bay on Tuesday. A
weak disturbance could bring a few showers north of Route 30
Tuesday afternoon...however most places will remain dry. Lows
overnight will dip into the upper 30s to lower 40s. Highs on
Tuesday will warm into the 50s.


Short term...(this evening through tuesday)
issued at 320 PM EDT Monday Apr 20 2015

Period will feature a steady feed of cooler/drier air under a
closed low that will meander into the northern Great Lakes.
Should be just enough residual boundary layer moisture and weak
ascent with a secondary feature to generate a few light
showers/sprinkles late this afternoon/evening. Dry with
diminishing winds otherwise tonight.

Mixed layer will become very deep during the day Tuesday on
southern fringe of negative height anomaly given late April
insolation and -30c temperatures at 500mb. This in combination with a
lingering/tight low level height gradient will ensure a windy
late morning/afternoon (gusts possibly approaching advisory
criteria)...and also allow highs to recover well into the 50s
(maybe 60f south) despite near zero 850 mb temperatures. Resulting steep
low level lapse rates under shear/pv axis may be enough to touch
off a few diurnally driven showers/sprinkles across the north as
models also show a decent amount of moisture in the 800-650mb


Long term...(tuesday night through monday)
issued at 320 PM EDT Monday Apr 20 2015

Deep cutoff low over Lake Superior will very slowly advance
eastward through the week...keeping our area under the influence
of northwest flow through the long term period. This will result
in temperatures 10 to 15 degrees below normal through at least
Saturday. Coldest portion of the airmass will arrive on Wednesday
with h850 temperatures forecast between -6c and -8c. As a
result...models have continued their downward trend for highs
during middle week. Temperatures may not get out of the low 40s in
portions of southern Michigan on Wednesday where clouds will
persist. Consistent westnorthwest winds of 5 to 10 miles per hour may be the
savior from a hard freeze in our area. Will need to monitor
closely for any night which may radiate out...considering hard
freeze thresholds would likely be met across at least the
northern half of the forecast area. Will continue to mention in
the severe weather potential statement for now and monitor later forecasts for any potential

Otherwise...dry Canadian air will keep our area dry through most
of the period. Did add slight chance probability of precipitation Wednesday night as a
weak wave rotates around the base of the large scale trough.
Removed superblend probability of precipitation over the weekend until models come into
better agreement with the exact location/timing of this ejecting


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 808 PM EDT Monday Apr 20 2015

VFR met conds through the taf valid period for northern in. Sig detail with respect to
surface winds amid northward lifting cyclone over northern Great Lakes to James Bay on
Tuesday. Marked/sig increases in sustained wind/gusts on Tuesday as deep
layer /sfc-2km/ lapse rates steepen considerably providing ample
momentum xfer of 30-40 knots flow down to surface.


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



short term...steinwedel
long term...Bentley

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