Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201842

Area Forecast Discussion
National Weather Service Northern Indiana
142 PM EST Mon Feb 20 2017

Issued at 130 PM EST Mon Feb 20 2017

Unseasonably mild conditions will continue through Friday. Dry
weather will persist through this evening, but an upper level
disturbance and frontal boundary will provide a likelihood of rain
showers late tonight into Tuesday. Mainly dry weather is then
expected for Tuesday night through Wednesday night before rain
chances increase once again by Thursday, and especially on Friday
as a stronger storm system approaches. There is a risk of some
severe weather on Friday with strong winds as the main threat.
The warmest conditions of the forecast period are expected on
Wednesday when highs are expected to range from the mid 60s to 70.
Temperatures will drop back to near seasonable normals by the
upcoming weekend with a chance of snow showers Saturday.


.SHORT TERM...(Today and Tonight)
Issued at 454 AM EST Mon Feb 20 2017

Dense fog over central IN/OH has been spreading slowly north early
this morning into an area which received good radiational cooling
earlier, and now is undergoing weak moisture advection on backside
of departing ridge. Expect this dense fog will impact at least our
srn counties before diurnal heating mixes it out later this
morning. Issued a dense fog advisory for this area based on
upstream obs and latest HRRR vsby fcsts. By afternoon, expecting
mostly sunny skies and soaring temps once again as a strong upper
level ridge moves across the area. Mixing heights should be
enhanced today by a stronger s-se pressure gradient. This should
allow temps to climb well into the 60s over most of the area again

Upper trof and accompanying sfc cdfnt movg into the Plains this
morning will weaken as it moves east tonight and Tuesday, but
still should be accompanied by sufficient moisture/forcing to
produce a band of showers as it moves across our area. Models have
come into better agreement on the timing of this trough passage
with the faster GFS slowing down toward earlier ECMWF/NAM
solutions. Thus, lowered pops tonight, especially across the sern
portion of the cwa. Gradient mixing and clouds combined with the
very warm airmass in place will keep temps from falling much
tonight, though evaporational cooling as showers move in should
cool off the nw over what would otherwise occur. Records for
highest minimum temperatures at SBN and FWA (45F in both
locations) should be broken tonight with lows ranging from the mid
40s ne to the mid 50s sw (around 50F at SBN/FWA).


.LONG TERM...(Tuesday through Sunday)
Issued at 454 AM EST Mon Feb 20 2017

Showers along the cdfnt Tue should mainly move east of the area
by early aftn. With only wk CAA behind the front and a very mild
start to the day, temps should be able to climb into the lower to
middle 60s once again. Shrtwv movg east from the nrn Plains to the
upr Grtlks on Wed will result in a very warm airmass movg into our
area with H85 temps climbing to >12C. Fairly strong low level
pressure gradient along with sunny skies should result in record
highs in the upper 60s to lower 70s. Cdfnt associated with this
shrtwv is expected to drop into our area Wed ngt psbly accompanied
by a few showers. Front will stall out in our area Thu as a strong
low develops over KS. This system will lift ne to near Lake
Michigan on Friday. As it approaches the stalled front over our
area will transition to a warm front and lift north Thursday night
resulting in showers and possibly thunderstorms as weak
instability and steep mid level lapse rates overspread the area.
As the low passes by to our north on Friday the cold front will
sweep across the area providing showers and psbly thunderstorms.
Strong wind fields in a high shear/low CAPE environment may result
in a squall line movg through the area with damaging wind
potential. Northwest flow in the wake of the low will bring  much
colder air and the potential for snow showers on Saturday. High
pressure will move across the area Sunday providing generally fair
weather, hwvr, some light snow is psbl over wrn portions of the
CWA in the aftn as WAA develops behind the retreating high.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 130 PM EST Mon Feb 20 2017

Southeast winds will continue to slowly ramp up this afternoon as
some shallow mixing develops after this morning`s strong low
level inversion. Strongest gradient across NW/portions of NC
Indiana should support strongest gusts around 20 knots at KSBN
this afternoon. An upper level short wave will lift east-northeast
across the western Great Lakes tonight allowing weak cold frontal
boundary to push into the area. Did maintain prevailing showers
following progression of this front late tonight/early Tuesday
morning but general weakening of upstream disturbance and weak
nature to the front could limit extent/duration of rain showers
to some degree. Did trend to mainly lower end MVFR conditions at
KSBN late tonight/early Tuesday morning with better pre-frontal
moisture push, with a brief period of IFR cigs not out of the
question. Moderate low level jet of around 40 knots will develop
tonight that could pose LLWS threat toward 12Z, but given marginal
nature and strong sfc gradient will hold off on mention.


LM...Small Craft Advisory until 4 AM EST Tuesday for LMZ043-046.




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