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Area forecast discussion 
National Weather Service northern Indiana
1044 am EDT Tuesday may 26 2015

issued at 358 am EDT Tuesday may 26 2015

An upper level disturbance will lift northeast today...and will
bring a good chance for thunderstorms to the area this afternoon.
More storms are possible Wednesday afternoon followed by dry
conditions Thursday through Thursday night. Temperatures will be
above normal for this time of year with highs warming into the middle
80s by Friday. There is a good chance for rain this weekend with
cooler temperatures.


issued at 1044 am EDT Tuesday may 26 2015

A few minor updates to the going forecast for this afternoon and
evening. Morning water vapor shows decent shortwave shearing
northeast as expected. Line of convection moving through Illinois is
associated with trailing convergent boundary. Vast majority of
latest guidance shows most of our County Warning Area getting at least a hundredth
of precipitation so bumped probability of precipitation into likely category. Severe weather threat
remains more nebulous given abundant prefrontal clouds...lackluster
forcing...and midlevel lapse rates below 6 c/km. That being said...
12z NAM...rap...and hrrr all show pockets of MLCAPE values around
1000 j/kg this afternoon. 0-6km bulk shear vectors are around 30 kts
with 0-3km values around 25 kts. Not really supportive of a
widespread/organized severe weather threat but a few clusters of
storms could become severe. This is especially true in our southeast
half given much less cloud cover...though wouldn't rule out the
northwest due to better forcing and shear. Damaging straight line
winds will definitely be the main concern given strong low level
flow...though an isolated tornado cant be ruled out due to decent
0-1km shear values and relatively low LCLs. Hail threat is
negligible. Expect storms to move into our western areas shortly
after noon and continue through the early evening hours. Will
continue to monitor satellite and surface observational trends for
any evidence of enhanced surface heating/moisture pooling through
midday as this line approaches. Again...severe risk is still
conditional at this point but certainly bears watching as the day
wears on.


Short term...(today and tonight)
issued at 358 am EDT Tuesday may 26 2015

Convectively enhanced southern stream SW over NE OK will dampen northeastward
through eastern Iowa today. However unlike yesterday upper jet streak aligned a bit
further eastward west/a more robust height falls overspreading County Warning Area this afternoon.
Upstream cloud evolution suggests pockets of insolation will develop
through morning west/at least a favorable yet limited surface based
destabilization response resulting. Eastward extent of more sig synoptic
scale forcing much in doubt however potential exists for upscale
organization organization to convn especially shld btr than expected
instability develop.

Regardless of outcome...following dryslot and increasing middle level
subsidence quick to follow this evening and other than a lingering
shower generally east have dropped probability of precipitation after 06z.


Long term...(wednesday through monday)
issued at 358 am EDT Tuesday may 26 2015

There are lots of challenges this long term period as the long wave
trough becomes reestablished over the western Continental U.S. After ejecting a
couple of short wave troughs across the central Continental U.S.. ahead of these
systems...plenty of moisture will be available for showers and
storms...albeit relatively stable middle level lapse rates will tend to
limit convection. Also...some upstream convection will tend to
intercept moisture flux and limit very deep moisture transport
north. Overall...the airmass over the central third of the Continental U.S. Has
had astounding precipitation efficiency...with Oklahoma City
approaching 20 inches of rain so far this month...well above the
record rainfall for any month in this city. With so much recent rain
upstream... there will likely be recycling of moisture as reflected
in research as what happened in the 1993 floods. Kept these factors
in mind with this portion of the forecast. Made only minor
adjustments to the timing and placement of shower and storms
Wednesday as the far southeast portion of an ejecting upper level
trough should be southeast sufficient to generate some storms...especially
with daytime heating. For this weekend...a slow moving southern
stream system will attempt to merge with a northern stream trough over
the upper Great Lakes region. Still some uncertainty on how this
will play out...but for now...rain chances at least at some point
look real favorable as the upper level trough interacts with the
surface boundary. As for temperatures...kept temperatures warm
Wednesday through Friday...with highs Friday well into the 80s as
supported by the GFS mex for the past several days.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 646 am EDT Tuesday may 26 2015

Increasing ll moisture flux ahead of ejecting upstream SW trough over
eastern Kansas resulting in rapidly eastward expanding MVFR ceilings. However
west/sunrise expect rapid mixing will ensue as ceiling heights settle out into
low bound VFR cu/SC. Decayed arc of earlier rain showers/thunderstorms and rain across eastern
MO/western Illinois mark the leading edge of height falls associated/west upstream SW
and as that system ejects rapidly northeastward into western WI lt this afternoon will
serve as the primary focusing mechanism for convn development in vicinity of the
terminals toward 18z. Degree of conv vigor much uncertain pending
evolution of warm sector cloud cover. Surface based destabilization expected
to be remain limited west/btr chances for upscale organization across Northwest
Ohio where more unstable conds may develop. Outside gradient wind gusts
at or above 25kts this afternoon...regardless brief period of gusty surface winds are possible
west/convn especially in vicinity of kfwa toward middle afternoon coincident west/core of 45kt low level jet


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