Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 222017

Area Forecast Discussion
National Weather Service Northern Indiana
317 PM EST Wed Feb 22 2017

Issued at 317 PM EST Wed Feb 22 2017

Clouds continue to slowly break up across the area today as dry
air works in allowing a chance for temps to rise into the mid to
upper 60s before the day ends. Clouds will slowly work back into
overnight tonight keeping lows in the upper 40s to mid 50s. Then
Thursday will have increasing chances for rain late as a low
pressure system approaches from the Plains. Severe weather is
possible on Friday as a front moves through the area. High temperatures
Thursday and Friday will be in the 60s before falling to more
seasonable temperatures for the weekend. As the cold air begins to
move into the region on Saturday, a chance for snow showers is


.SHORT TERM...(This Evening through Thursday)
Issued at 316 PM EST Wed Feb 22 2017

Weather issues mainly revolve around pesky stratus and impacts on
well above normal temperatures most of the period before rain
chances increase.

Thinning/breaks in the stratus continue to occur allowing for
pockets of substantial heating of well above normal temperatures
just above the surface. Condition of stratus remains questionable
going into tonight as weak frontal boundary sinks southeast and
potentially stalls somewhere over the forecast area into Thursday
before being pushed north Friday (more details in Long term). The
front may limit scouring of moisture, especially in the southeastern
half of the area leading to some fog/stratus potential overnight
into Thursday. Will continue with trends of some clearing behind the
front in the NW but keep clouds in place with no mention of fog for
the time being. Lows tonight along and southeast of the front will
only fall off into the upper 40s to middle 50s, vs behind the front
in the lower to middle 40s. Highs Thursday will be dependent on the
resting position of the front and clouds both associated with the
front as well as expected to arrive from the south as moisture
further increases and rain chances begin to increase from SW to NE.
Large range in temps expected ranging from the 50s in the NW behind
the front to well into the 60s in the SE.


.LONG TERM...(Thursday Night through Wednesday)
Issued at 316 PM EST Wed Feb 22 2017

Frontal boundary will begin to edge northward into early Friday with
increasing low level jet keeping flow of warmer as well as
increasingly humid air. Most locations should see at least a round
of 2 of showers and possibly a few storms Thursday night into early
Friday before the frontal boundary clears the area. This will then
set the stage for potential severe weather concerns Friday afternoon
and evening. Models generally agreeing on at least several hundred
J/KG of CAPE in the warm sector Friday afternoon and evening with
dewpoints in the middle 50s to possibly near 60. Steep mid level
lapse rates in excess of 8 C/Km, strong forcing and increasing shear
will make for a potentially volatile atmosphere for a pre frontal
trough (possibly as early as 18 to 21Z)  and then main cold front to
move through. Challenges still remain in exact phasing of key
features but enough potential there to warrant Enhanced risk of
severe from SPC. Most likely modes of convection will be potential
for discrete cells along pre frontal trough that would converge into
a squall line. Additional line of storms may also develop with the
main front and rapidly approach/possibly merge with more eastern
convection. Threat of tornadoes cannot be ruled out given what will
likely be low LCL`s and strong shear/helicity. Parameters of this
magnitude are more common for a spring weather outbreak vs late

Once the cold front passes, mother nature will remind the region it
is still February with falling temperatures and highs in the 30s for
the weekend. Disjointed surface low development will preclude any
lake effect potential until maybe Sat when additional energy rotates
through and brings a mixture of rain and snow eventually changing to
all snow Sat afternoon and evening. Little if any accumulation

Temperatures will begin to moderate for the start of the work week,
heading back to somewhat more seasonable levels and eventually above
normal by mid week with additional chances for rain through the
period, especially mid week.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1233 PM EST Wed Feb 22 2017

Morning LL cloud cover and VISBY reductions were dissipating as
drier air worked into the region. Expecting cloud decks within MVFR
criteria, but some breaks to VFR are possible especially at SBN.
Then as we move into the overnight hours, low level moisture moves
back in, but a low level jet between 30 and 40kts passes overhead
allowing sfc winds to be too strong for widespread fog, however
there appears to be a better chance for low level stratus/br. Shear
appears marginal as the jet passes overhead so have left it out of
this issuance.




LONG TERM...Fisher

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