Area Forecast Discussion
Issued by NWS Northern Indiana

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652
FXUS63 KIWX 170711
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
211 AM EST Fri Nov 17 2017

.SYNOPSIS...
Issued at 305 PM EST Thu Nov 16 2017

Cool and cloudy conditions will persist through Friday with lows
around 30 and highs on Friday in the mid to upper 40s. Widespread
rain is expected on Saturday. Rainfall amounts around an inch are
expected for most locations with isolated amounts up to around two
inches possible. This could cause minor flooding in low lying and
poor drainage areas. Thunderstorms are also possible but no severe
weather is expected. Some light lake effect snow will then be
possible Sunday morning but little to no accumulation is expected.
Dry and seasonable temperatures are anticipated for next week.

&&

.SHORT TERM...(Today and Tonight)
Issued at 205 AM EST Fri Nov 17 2017

Brief period of quiet weather to begin the short term as surface
high pressure moves off to the eastern great lakes leading to a
breezy southerly return flow over our area this afternoon. This
will have highs today 5-10F warmer than yesterday and closer to
seasonal norms.

Focus then shifts to strong southern stream energy that will
accompany next system approaching the area tonight. 00Z obs showing
150kt speed max in upper jet over western US that will move quickly
eastward into our region with progressive...positively tilted upper
trough. Rapidly developing surface low to the west will have
enhanced moisture return ahead of it aided by strong 60kt LLJ which
will have over-running precip shield ahead of approaching warm front
overspread the forecast area tonight. Nose of LLJ surges north of
our area and should focus heavier precip just to our north...but
still could see up to 0.50 inch overnight. WAA will have little
diurnal change in temps as readings remain in the 40s thru the
night before rising into the lower 50s by early Saturday morning.

&&

.LONG TERM...(Saturday through Thursday)
Issued at 205 AM EST Fri Nov 17 2017

Surface low continues to deepen as it moves into the area on
Saturday. System will have strong upper level support as
divergence associated with left exit region of upper jet will be
over the area. Strong forcing and abundant moisture with PW
greater than 1 inch will bring heavier rain potential with an
additional inch or more expected Saturday. Forecast soundings do
indicate some elevated instability...especially SE CWA...and CAMs
also hinting at some embedded convective elements but nothing to
suggest much of a severe potential attm. While storm total precip
could approach 2 inches locally...progressive nature of this
system should preclude any long duration heavy rain in any one
location so flash flooding not expected to be a threat but
temporary ponding in poor drainage and low-lying areas possible.

System lifts rapidly northeast Saturday night...reaching southern
Quebec by Sunday morning. This will bring a brief but favorable
setup for LES. Unidirectional NW flow beneath 5Kft inversion will
favor a multi-band setup for roughly an 18-21 hour window.
Limiting factors will be previous days temps into the 50s and a
thermal profile that has the DGZ above the cloud bearing layer. If
a dominant band does form within the multi-band could see a quick
inch or so accumulation on grassy areas but best suited for a
near-term forecast. Backing winds with surface ridging building
into the TN valley will bring an end to LES late in the day Sunday
and bring a quiet weather pattern to the region for much of the
remainder of the long term period. Northern stream system moving
across southern Canada will bring a cold front through the area on
Tuesday but high pressure remains anchored just off the Carolina
coast and blocking any return flow to support precip chances with
the fropa. Northerly flow behind the front may bring LES back into
play on Wednesday but will keep forecast dry for now. High
pressure builds back into the area to end the period and should
bring a cool but pleasant Thanksgiving.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1206 AM EST Fri Nov 17 2017

Stratocu locked in under post frontal inversion within low level
anticyclone expected to persist through late morning before
eroding/mixing out in response to rapidly escalating warm advection.
Wrn bound of anticyclone quite dry and will hold off til mid evening
before introducing MVFR mention as shra develop across the terminals.
Otherwise substantial LLWS expected from roughly 00-09Z tonight.

Widespread LIFR conditions likely thereafter and just beyond this
period. Will address in later fcsts.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory from 7 AM this morning to 3 AM EST Saturday
     for LMZ043-046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...JAL
LONG TERM...JAL
AVIATION...T


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