Scientific Forecaster Discussion
fxus63 kiwx 251029
Area forecast discussion
National Weather Service northern Indiana
629 am EDT Tue Jul 25 2017
issued at 409 am EDT Tuesday Jul 25 2017
High pressure will provide another comfortable day with relatively
low humidity and high temperatures near 80. A brief warmup will
occur Wednesday prior to the arrival of a cold front. Highs will
reach the middle 80s with slightly higher humidity. Showers and
thunderstorms are likely late Wednesday night into Thursday. Some
storms could be severe along with heavy rainfall, especially over
North Central Indiana. Drier and cooler conditions will return
Friday and continue into the weekend.
Short term...(today and tonight)
issued at 408 am EDT Tue Jul 25 2017
Quiet and comfortable weather for late July expected through
Wednesday. High pressure centered over the Great Lakes will
continue to slowly slide east today. Highs expected to top out
near 80 with comfortable dew points in the 50s to lower 60s. As
the high moves to the mid Atlantic region on Wednesday low level
flow will become more southerly allowing a return of low level
moisture. Dew points will creep up slowly during the day but
should remain in the 60s. Coupled with temps into the lower and
middle 80s it will feel a little more humid, especially in the
southwest, but nothing oppressive.
Long term...(wednesday through monday)
issued at 408 am EDT Tue Jul 25 2017
Focus in the long term period is Wednesday night and Thursday with
possibility of mesoscale convective system producing severe weather and heavy rainfall once
again. Outside of this system, remainder of long term looks quiet
and quite comfortable for late July.
Moisture will continue spreading northeast Wednesday night ahead of
a strong short wave and approaching cold front. Models coming closer
together on timing of this system. Seasonably deep and convectively
enhanced low pressure is shown by most models to develop along
surface front late Wednesday and move into western County Warning Area overnight.
Strong deep layer shear on order of 50-60 knots expected as mid
level flow increases. Surface low a concern as low level winds back
significantly yielding strong low level directional shear. Overnight
timing though complicates severe potential as instability is limited
with MUCAPES between 1000-1500 j/kg. However, this may be enough to
sustain approaching mesoscale convective system into our southwest counties with a severe
wind risk and even an isolated tornado possibility if winds
indeed back near the warm front.
Heavy rainfall and possible flooding just as much of a concern as
model pwats are well over 2 inches and warm frontal boundary will be
near southern counties that have seen their share of heavy rainfall
over last month. Low level jet of 30-35 knts coincident with Theta-E
surge is focused into this region and being lifted over warm front.
Rainfall amounts of 1 to 2 inches look easily obtainable and locally
higher amounts not out of question if storms train north of surface
Lingering showers and storms expected Thursday with decreasing pcpn
chances from west to east during the day. High pressure then moves
back in to the Great Lakes and remains in place through the weekend.
Fast moving weak short wave may move through the region late in the
weekend or early next week but pcpn chances and amounts look small
at this time.
Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 627 am EDT Tue Jul 25 2017
High pressure ridge over the area this morning will move east with
associated dry airmass resulting continued VFR conditions today
and tonight. Some ground fog being reported in rural locations
early this morning but not likely to impact sbn/FWA. Just a few cu
and cirrus debris from convection over the upr Midwest expected at
the terminals over the next 24hrs. Light east winds will veer to
se tonight advecting in a little more low level moisture, so some
potential for br late tonight but given expected wk gradient and
high clouds, felt confidence in restricted vsbys too low to add
mention in tafs attm.
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