Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 171041

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

Issued at 205 AM EST Fri Nov 17 2017

Considerable clouds and continued cool today with highs in the mid
40s. Rain develops tonight with thunder possible late. Periods of
rain Saturday give way to gusty northwest winds and falling
afternoon temperatures. Look for early morning highs in the 50s.


.SHORT TERM...(Today and Tonight)
Issued at 540 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 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 12Z TAFS through 12Z Saturday Morning)
Issued at 540 AM EST Fri Nov 17 2017

Wrn bound of stratocu within weakening post frontal inversion along
retreating low level anticyclone expected to erode out toward the
noon hour as as strong warm advection spreads across the terminals.
Wrn periphery of low level anticyclone quite dry yet sig return
moisture flux expected this evening with rapid shra/isold tsra
development likely by late evening. This also corresponds to peaking
LLJ with substantial LLWS from roughly 03-09Z tonight.

Thereafter widespread LIFR conditions likely invof of KSBN within
cold side of sfc cyclone late tonight and by aftn at KFWA.


LM...Small Craft Advisory from 7 AM this morning to 3 AM EST Saturday
     for LMZ043-046.




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