Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 170552

Area Forecast Discussion
National Weather Service Northern Indiana
150 AM EDT WED AUG 17 2016

Issued at 150 AM EDT Wed Aug 17 2016

Fair weather is expected into this afternon as weak high pressure
builds in from the west. Light winds and clearing skies will
result in patchy fog in some areas by daybreak. A weak upper level
trough will move across the Great Lakes this afternoon, potentially
yielding a few showers and storms in our area. A stronger cold front
is expected to move across the region over the weekend bringing a
good chance of rain. Highs through the remainder of the work week
will generally be in the low to mid 80s with lows in the mid to
upper 60s.


Issued at 749 pm EDT Tue Aug 16 2016

Latest nam bufr soundings, hrrr, and mav mos suggests decent
potential for fog development late tonight. Dwpts this eve still
in the m-u60s across the area with light winds and fcst lows near
or blo these values. Added patchy fog to fcst for roughly sern 2/3
late tonight as dry air advection behind today`s wk cdfnt may
limit fog development in the west.


.SHORT TERM...(This Evening through Wednesday)
Issued at 334 PM EDT Tue Aug 16 2016

St. Joseph County (IN) EMA reports flooding is still ongoing across
South Bend and adjacent areas. Therefore plan to issue another (more
narrow) areal flood warning to extend through the night once the
current warning expires at 2015Z.

A few lingering showers in our south this evening as
elongated/positively tilted trough and associated convergent
boundary slowly push out of our area. Brief respite from rain
expected overnight as weak shortwave ridge/subsidence slide over the
area. Should see at least some partial clearing in our NW half
overnight with some light cool/dry air advection leading to
overnight lows in the mid to upper 60s. Some concern for patchy fog
or stratus toward daybreak given light surface winds and recent rain.
Forecast soundings and MOS guidance don`t show a great signal for
widespread or dense fog but some patchy fog may be possible. Since
confidence in impacts is low, will leave out of the forecast for now.

Next northern stream shortwave, already over the Northern Plains,
will pass through the Great Lakes and bring another low chance for
showers tomorrow. CVA forcing is weak and focused mainly over
Michigan. Low level convergence signal is also broad and weak. Still
some decent low level moisture though and this yields over 1000 j/kg
of 0-1km MLCAPE across parts of our area. A few showers and storms
can`t be ruled out, especially across our north during the late
afternoon and evening but lack of coherent forcing should keep them
isolated. Severe weather not currently expected, but an isolated
damaging wind gust could be possible if NAM instability profiles
verify and storms do actually develop. Brief, isolated mod-heavy
rain could also be possible but will be absolutely nothing like last
night`s event.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 334 PM EDT Tue Aug 16 2016

Primarily dry conditions expected Thursday and Friday as mid/upper
level ridge builds over the region. Main focus of WAA/isentropic
ascent will be north of our area. Surface dewpoints will remain near
70F and modest instability could support an isolated storm if any
subtle trigger can develop in our area. For now, will refrain from
broadbrushing low POP`s and maintain previous dry forecast but some
slight chances may need to be introduced (especially on Thursday) as
we draw closer to this time period. Heat and humidity will build
somewhat. Thermal profiles not particularly hot but could see highs
approach the upper 80s with heat indices perhaps in the low-mid 90s.

Next good chance of rain will arrive late Saturday and possibly into
Sunday. Still a lot of model disagreement on how exactly this next
system will evolve but do expect formidable longwave trough and
associated cold front to bring rain to most of the area at some
point this weekend. GFS is drier and more progressive compared to
12Z ECMWF which keeps chance of rain through Sunday night. Stayed
close to consensus POP`s given this time range, though did try to
highlight Saturday night with the best chances. Cooler and drier
early next week.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday Evening)
Issued at 150 AM EDT Wed Aug 17 2016

Radiational cooling underneath thinly vieled cirrus plume leading to
xpcd fog development at this hour yet nr term guidance
trends continue to back off prior IFR cat fog. Given xpcd lack of
bndry lyr mixing and degree of low level moisture in place will keep
w/close w/prior fcst. Otrws rapid improvement to VFR xpcd through
mid morning.


.IWX Watches/Warnings/Advisories...



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