Scientific Forecaster Discussion
fxus63 kiwx 180511
Area forecast discussion
National Weather Service northern Indiana
111 am EDT Wed Sep 18 2019
issued at 707 PM EDT Tue Sep 17 2019
Mostly clear skies are expected tonight, but some patchy fog
could develop near sunrise. Low temperatures Wednesday morning
will be in the middle to upper 50s. Mostly sunny skies are
expected Wednesday with high temperatures warming into the lower
to middle 80s. Slightly warmer temperatures are forecast for
Thursday and Friday with highs mainly in the middle to upper 80s.
The next chance of rain is not expected until this weekend.
Short term...(this evening through wednesday)
issued at 342 PM EDT Tue Sep 17 2019
Quiet weather to continue in the short term period with slowly
moderating temperatures into mid week.
Fog and stratus was slow to burn off today, with last of stratus
continuing to slowly dissipate across south central lower Michigan
and across extreme southwest portions of the area. The main
forecast challenge tonight is on potential fog/stratus
redevelopment for Wednesday morning. Overall synoptic setup is
somewhat similar tonight in comparison to last night, but slightly
less favorable hydrolapse profiles and slightly lower crossover
temps may tend to discourage dense fog formation. May have to
watch areas which were slower to erode stratus this afternoon (far
NE and far SW portions of forecast area) for perhaps best chance
of fog formation.
A couple of short waves will top ridge tonight into Wednesday
across the upper MS valley/northern Great Lakes. This waves will
do little to suppress the background upper ridge across the area.
After some patchy morning fog, skies should be mostly sunny for
Wednesday with warmer conditions in the lower 80s for most areas.
Long term...(wednesday night through tuesday)
issued at 342 PM EDT Tue Sep 17 2019
Longwave pattern will remain stagnant Wed night into Thursday
with blocking pattern persisting across the western Atlantic.
Slight eastward progression of central Continental U.S. Ridge axis by
Thursday will allow for more noticeable warm up by Thursday
afternoon when highs in the mid 80s become more likely. Moisture
transport will also be on the slow increase by Thursday night into
Friday as next large scale upper across western Continental U.S. Shifts
east. Medium range guidance still differs in the handling of this
next longwave trough, with operational GFS dampening it more
quickly in a more progressive fashion into the weekend, while ec
tends to be slower and stronger. Given the large spread in
guidance this energy still off the British Columbia Canada coast, opted to not
steer far from blended guidance in regards to pops for Saturday-
Sunday, with greatest pops in the high chance/low likely range
from Saturday night into Sunday. Still too early to get too depth
in terms of severe potential, but a good deal of question at this
forecast distance in terms of destabilization given what should be
a fairly expansive mid level thermal ridge in place. Some decent
rainfall amounts will be a possibility with potential of an
efficient frontal response, but details in this regard will depend
on how evolution of larger scale trough verifies. Cooler and less
humid weather moves in for early next week behind the front.
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1232 am EDT Wed Sep 18 2019
VFR conditions should prevail for the majority of the 06z taf
cycle. The exception will be the potential for patchy ground fog
to affect the terminals around daybreak. Have maintained tempo
group from previous taf cycle for kfwa. There is some potential
for ground fog to also impact ksbn given the recent minor visby
drop at kekm and kmgc. Will hold off on inserting a tempo for
ksbn with this issuance, but will monitor trends closely nearing
Winds shift more out of the south-southeast during the day while remaining
less than 10kt.
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