Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 141958

Area Forecast Discussion
National Weather Service Northern Indiana
358 PM EDT Thu Sep 14 2017

Issued at 346 PM EDT Thu Sep 14 2017

Skies will become partly cloudy to mostly clear this evening as an
upper level disturbance continues to pull away from the region.
Areas of fog are expected to develop once again tonight, with some
patchy dense fog a possibility for late tonight into early Friday
morning. Low temperatures tonight will drop into the mid 50s, with
warmer high temperatures on Friday into the 75 to 80 degree range.
The warming trend will continue into the weekend with highs in the
lower to mid 80s for Saturday and Sunday. The next chance of
showers and thunderstorms will arrive for Sunday afternoon through


.SHORT TERM...(This Evening through Friday)
Issued at 346 PM EDT Thu Sep 14 2017

Quiet weather to continue in the short term with the primary near
term concern on fog potential once again later tonight into early
Friday morning.

Widespread dense fog earlier this morning has mixed out to low
cloud deck and has scattered across much of western half of the
forecast area. Low clouds will maintain longer duration across far
northeast Indiana and northwest Ohio in closer proximity to
remnant low level cyclonic circulation. Expecting gradual
decreasing coverage of these low clouds across the east but have
some lower confidence in low cloud coverage duration across these
locations this evening as some near term model guidance hangs
onto higher low level RH into the evening.

Overall stagnant/stable wave pattern will lead to some potential of
patchy fog formation once again tonight. Some favorable factors
for fog potential tonight include continued dry mid level air,
relatively high crossover temps, and continued weak wind field.
Some weak return southerly flow is expected late tonight however
as low level anticyclone slowly nudges eastward. Given above
factors did add fog mention again tonight, with greatest coverage
expected across eastern half of the forecast area where crossover
temps may hold up a bit higher this afternoon due to longer
duration of low clouds/weaker mixing. Some patchy dense fog is
possible once again, although currently not expecting dense fog to
be as widespread as this morning.

Upstream upper level ridge will build into the region on Friday as
it amplifies, with mostly sunny/partly cloudy skies. Thermal
advective pattern remains weak through Friday in this stagnant
pattern, but good deal of insolation on Friday should allow high
temperatures into the 75 to 80 degree range.


.LONG TERM...(Friday Night through Thursday)
Issued at 346 PM EDT Thu Sep 14 2017

For Friday night through the weekend, main synoptic feature of
interest will be evolution of large scale upper trough across the
Pacific Northwest this afternoon. Stronger low level moisture
transport and frontal convergence will remain well west of the
local area through Saturday night across the Plains. The next
chance of rain showers should hold off until Sunday afternoon/night
when the strong upper level trough lifts northeast across south
central Canada, eventually dragging weak cool front southward
across the southern Great Lakes. Did maintain low-mid chance PoPs
across the northwest ahead of this front on Sunday due to some
expected pooled pre-frontal moisture. Did maintain an isolated
thunder mention Sunday/Sunday evening, but upper ridge in place
across the area will not be fully dampened by this wave, and wind
shear will remain quite weak. Not expecting any severe threat at
this time due to the combination of weak instability axis with
prefrontal moisture axis and weak shear.

Cold frontal boundary will not progress significantly southward on
Monday as forcing lifts across Hudson Bay area, but additional
weak short waves in southwest upper flow may result in periodic
stronger warm advection episodes and had to broadbrush chance PoPs
for Monday night/Tuesday. Also have introduced chance PoPs for
midweek with some indications in medium range models of stronger
short wave lifting across Mid MS Valley, resulting in eastward
translation of stronger low level jet into the region. Confidence
remains on the high side in terms of a return to above normal
temps by midweek after weak early week fropa.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 123 PM EDT Thu Sep 14 2017

Morning flight restrictions have been able to rise within diurnal
processes towards VFR conditions for this afternoon at both sites.
Winds become weak and cross-over temps become favorable for br
tonight. Dew point depressions and sfc moisture are moist enough
for br as well, but appear to be lower in magnitude Friday morning
than this morning. Feel that FWA has a better chance at br than
SBN with greater sfc moisture left over there and think at least a
lowering into MVFR is likely and it may go into IFR at FWA.




SHORT TERM...Marsili
LONG TERM...Marsili

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