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Area forecast discussion 
National Weather Service northern Indiana
314 PM EDT Tuesday Jul 28 2015

issued at 311 PM EDT Tuesday Jul 28 2015

High pressure across the Great Lakes will continue to provide
warm and humid conditions. This high will begin to shift to the
east tonight. Increasing moisture will bring increasing chances of
showers and thunderstorms late tonight..and a cold front will pass
through Wednesday producing another round of showers and

Lows tonight will be near 70. Highs on Wednesday will range from
lower 80s near Lake Michigan to upper 80s in Northwest Ohio.


Short term...(this evening through wednesday)
issued at 311 PM EDT Tuesday Jul 28 2015

Quiet weather for tonight. Threat of showers / thunderstorms early
Wednesday and again Wednesday afternoon.

500 mb ridge over the lower Mississippi River valley will move little
for the near term. Upper level trough and associated surface low deepens
in the Lee of the Canadian rockies overnight...and this in turn will
flatten the ridge ever so slightly by daybreak Wednesday.

Overnight...boundary layer moisture and instability will increase ahead
of the decaying surface front. Convection over the northern
plains/upper Mississippi River valley will push eastward overnight
and expect to see the remnants spread into the western third of
the forecast area early during the day.

Cloud cover will play a big role as to whether or not the
instability can be fully realized as the weak frontal boundary
pushes through the area during the late afternoon/early evening.
This looks to be a similar setup to favor rapid convective
development combined with shear along the front...could not rule
out funnel/land spout formation. Additionally...storms that do
develop will be very efficient rain producers and expect that
there will be isolated rainfall reports approaching 0.75 to 1.00


Long term...(wednesday night through tuesday)
issued at 311 PM EDT Tuesday Jul 28 2015

Surface cold front associated with weak short wave rotating around
base of large upper low over Canada will be exiting the area at
beginning of period Wednesday evening. Nam12 remains one of slower
models with secondary development along 850mb moisture gradient with
weak short wave. Most other guidance on agreement with front and
precipitation chances exiting the southeast early in the evening. Will keep a
slight chance mention for continuity at this time range.

High pressure then moves in through Friday. Upper level ridge
retrogrades and builds west while northwest flow aloft develops once
again over the Midwest and Great Lakes region. This should set the
stage for numerous small scale perturbations which will fly through
from time to time. Expect modest to strong instability at times
given still moist lower levels and cooling aloft. A weak short wave
and surface front indicated for Friday night but poor timing and lack of
strong moisture return initially so will keep this period precipitation free
for now. Will continue with low pop chances later in the weekend
into early next week with several more weak short waves. Confidence
in timing low but will maintain continuity with previous forecast
and superblend init and latest model output.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 311 PM EDT Tuesday Jul 28 2015

(for the 18z tafs through 18z Wednesday afternoon)
issued at 119 PM EDT Tuesday Jul 28 2015

Ridge over the Great Lakes will persist...gradually weakening and
shifting east overnight. Winds remain light with VFR conditions
through 12utc. Approaching cold front and decaying convection from
the plains will enter the western third of the area between
12-15utc. Winds become more southerly and begin to increase as
well. Rain showers spread west to east and expect isolated -tsra after 15utc.

While not included in either taf...later in the forecast period
will have to monitor for possible low level wind shear as the boundary layer mixes
out and low- level winds begin to increase ahead of the middle level


Iwx watches/warnings/advisories...


short term...Lewis
long term...Lashley

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