Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 271139

Area Forecast Discussion
National Weather Service Northern Indiana
639 AM EST Sun Nov 27 2016

Issued at 345 AM EST Sun Nov 27 2016

Highs today are expected to reach the mid to upper 40s under partly
sunny skies. A strong low pressure system will bring widespread rain
to the area beginning early Monday morning and continuing through
Monday night. Storm total rainfall amounts of up to an inch are
possible. Mild temperatures are expected through Wednesday but
cooler conditions will return by the end of the week.


.SHORT TERM...(Today and Tonight)
Issued at 345 AM EST Sun Nov 27 2016

Relatively quiet weather on tap for today as mid/upper level ridge
axis moves over the Great Lakes. However, still a tricky cloud/temp
forecast. Some indications in latest hi-res guidance that low level
moisture plume currently over Missouri will expand into our area
with just enough saturation under strong subsidence inversion to
generate potential for renewal of low cloud deck. Confidence in this
scenario is low however, given thin and muted signal in forecast
soundings/RH fields and generally over-aggressive hi-res guidance
but very low sun angle, strong inversion, and upstream obs do
support at least some potential. Suspect more of a SCT/transient low
cloud deck over our area today with best chances in the NW. Have
tempered inherited cloud forecast a bit but still on the pessimistic
side with just partly sunny conditions. Maintained mid/upper 40s for
highs but there is bust potential either way and will depend on
exactly if/where stratus sets up. A few sites reporting fog/BR this
morning but decent surface gradient should keep chances for
widespread/dense fog low.

Much higher confidence in expanding clouds and precip chances
overnight. First piece of western CONUS conglomerate trough will
swing into the Upper Midwest and support strong surface
cyclogenesis by tonight. Strengthening LLJ/WAA downstream will
support moderate 295K isentropic ascent. As previously mentioned,
highly meridional flow with large NW displacement of gradually
occluding system will limit more focused warm frontal response but
still enough broad ascent in moist environment to support numerous,
light rain showers by early Monday morning. Surface wet bulb temps
warm enough for entirely liquid event, even in far NE corner of


.LONG TERM...(Monday through Saturday)
Issued at 345 AM EST Sun Nov 27 2016

Better chance for more widespread/moderate rain will arrive later on
Monday.  Secondary, embedded shortwave will swing directly overhead
and support strong QG omega along passing occluded front. 50-60 kt
LLJ pushes 295K mixing ratios over 6 g/kg and PW values to around 1
inch. Enough reduced stability for an efficient response to
synoptically-driven uvm but paltry midlevel lapse rates and
cool/stable conditions below 800mb will likely prevent thunder.
Still, could see storm total rainfall amounts of up to an inch in
many locations given quality of moisture transport and passing
midlevel vort max.

Forecast confidence for the middle and end of the week remains low.
Deterministic models continue to struggle with placement and
evolution of final jet streak/wave rounding base of large trough.
Several of latest runs suggesting chance for rain Wed and Wed night
but have held with just low chance PoPs in far SE Wed evening for
now. Lake effect/enhanced precip will then ramp up later in the week
with broad/cool cyclonic flow over the Great Lakes. Still too early
to discuss exact timing/amounts as that will depend on final low
level flow trajectories and timing of any subtle embedded
shortwaves. Snow may mix in at times but airmass still does not
appear particularly cold and chances for any meaningful accumulation
are still on the low side.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 554 AM EST Sun Nov 27 2016

Low level moisture return along western periphery of anticyclone
to the east has resulted in the northeast advection of
fog/stratus into northern Illinois. Latest few satellite images
also starting to depict some southward expansion of stratus along
Lake Michigan shoreline. Expecting stratus to continue to
develop/advect northeast this morning with greater confidence in
impacts to KSBN. Still lower confidence in regards to cloud base
heights however, but have opted to include IFR mention late
morning/early afternoon at KSBN. Maturing warm sector should
eventually take focus for fog/stratus north of KSBN this evening.
Confidence in forecast is even lower for KFWA with more
uncertainty as to eastern extent of stratus. Will continue with
optimistic forecast at KFWA and maintain VFR conditions with more
favorable low level trajectories in terms of moisture transport
across northwest Indiana. Low level flow to ramp up tonight and
have included LLWS mention after 06Z, along with onset of rain
from west to east during the late tonight/early Monday morning


LM...Gale Watch from late tonight through Monday evening for LMZ043-




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