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Area forecast discussion 
National Weather Service northern Indiana
655 am EDT Friday may 29 2015

Synopsis...
issued at 355 am EDT Friday may 29 2015

Scattered showers and thunderstorms are expected today as an
unstable airmass overspreads the area ahead of a cold front
approaching from the upper Midwest. Coverage of the showers and
thunderstorms is expected to increase from northwest to southeast
across the area late tonight and Saturday as the front moves into
the area. Highs today will be in the lower to middle 80s... with
lows tonight mainly in the middle to upper 60s. Much cooler
temperatures will overspread the area behind the cold front this
weekend... with highs by Sunday only in the lower to middle 60s.

&&

Short term...(today and tonight)
issued at 355 am EDT Friday may 29 2015

Cold front over the northern plains/upper Midwest this morning is expected to
move southeast to near the northwest border of our County Warning Area by Saturday morning.
S-SW flow developing ahead of the front and associated upper level trough
was advecting deep moisture back into our County Warning Area with precipitation water
forecast to exceed 1.5" today. Diurnal heating should lead to
1000-1500j/kg MLCAPE this afternoon. Vorticity maximum over northern Kentucky expected to
lift north-NE across western Ohio this morning while weak shortwave over MO lifts
NE across northwestern portion of our area later today providing a couple
of weak forcing mechanisms. Given the weak-moderate developing instability
today expect this forcing will be sufficient to trigger scattered
showers/thunderstorms with strongest convection during the afternoon. Although
0-6km shear only expected to be in the 20-25kt range today... some
lingering dry air aloft and steep low level lapse rates should
result in gusty winds and possibly small hail in strongest cells this
afternoon... but severe storms are not expected. Should be sufficient
sunshine/gradient mixing for boundary layer depth up to around
850mb again today resulting in highs in the l-m80s.

As cold front/upper trough approaches overnight coverage of showers should
increase from northwest-southeast across the area... forecast probability of precipitation range from likely
northwest to chance southeast. Given very moist airmass ahead of the cold front/upper trough
and deepening warm cloud layer... some potential for locally heavy
rainfall... but with just weak instability expected and stronger
forcing moving in late... stayed close to fairly low wpc quantitative precipitation forecast for this
timeframe. Modest southerly flow and considerable cloud cover should
limit temperature falls tonight...forecast mins in the M-u60s...but there is
considerable uncertainty... mainly near Lake Michigan where GFS
is a little faster with frontal passage than NAM... yielding 10f MOS min temperature
difference.

&&

Long term...(saturday through thursday)
issued at 355 am EDT Friday may 29 2015

Focus will remain on cold front which will sweep southeast across
the region Saturday. Plenty of low level moisture will reside along and
ahead of the front with precipitable waters in excess of 1.5 inches. Increasing
chances for showers and thunderstorms should occur...but may end up
more behind the front where best forcing resides. Ahead of the
front...cloud cover and early timing of the front may limit
convective development and organization. In addition...only a narrow
window of slightly increased lapse rates and instability is possible
ahead of the front across mainly the southeast half. This appears to line
up with new day 2 severe weather outlook depicting a marginal risk
of severe storms. Putting it all together yields continuation of
likely probability of precipitation all areas in the morning and confined to southeast afternoon
with a passing mention of strong storms in the severe weather potential statement.

Colder air will move in as 2 surges...the first being the largest
drop as 850 mb temperatures drop to around 10 c. Front may stall out Sat
night into Sunday in far southeast sections as a second trough and somewhat
colder air drop into the area. Showers and maybe a rumble of thunder
could linger until the front finally clears the area. Toned down
probability of precipitation in this period and tried to add a bit more timing detail.

Dry forecast will be in store Sunday night into at least Wednesday
night with temperatures somewhat sluggish to increase at first. Strong
early June sun and increasing upper level heights should allow for a
rapid uptick in both temperatures and moisture middle to late week.
Afternoon/evening convection will become possible starting as early
as Thursday as instability builds. However...medium range models all
suggest no strong signals for triggers for more widespread
convection at this time with warm front well north of the area.
Superblend of models tries to increase precipitation chances and at this
time will hold off on raising as chances will likely be more keyed
in on outflow boundaries and left over complexes that may move in
from upstream.

&&

Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 652 am EDT Friday may 29 2015

VFR ceilings expected to form this morning as airmass destabilizes.
Rain showers lifting north into Northwest Ohio at this time should remain east of FWA but
diurnal heating and weak shortwave lifting NE across Illinois should cause
scattered rain showers/thunderstorms and rain to develop this aftn/eve...especially over Northwest
Indiana. Lull in convection then expected much of the night with
rain showers and possibly ts spreading back into Northwest Indiana late tonight as
cold front approaches. Whether rain showers occur late tonight or not... expect
MVFR ceilings/visibilities to develop by that time as moist low levels
saturate.

&&

Iwx watches/warnings/advisories...
in...none.
Michigan...none.
Ohio...none.
Lm...none.
&&

$$

Synopsis...jt
short term...jt
long term...Fisher
aviation...jt



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