Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 220849

Area Forecast Discussion
National Weather Service Northern Indiana
449 AM EDT Thu Mar 22 2018

Issued at 449 AM EDT Thu Mar 22 2018

Cool and dry northerly flow is expected through the rest of the
week. Lows will generally be in the 20s with highs in the 40s. A
storm system will likely bring several inches of wet snow to areas
mainly south of US 24 and west of interstate 69 in Indiana later
Friday night into Saturday. Drier air then returns Sunday into
Monday, with temperatures warming from the mid 30s to low 40s
Saturday to near 50 degrees by Monday. Rain chances increase along
with warmer temperatures for Tuesday and Wednesday.


.SHORT TERM...(Today through Friday)
Issued at 445 AM EDT Thu Mar 22 2018

Quiet and dry weather in the short term before a more active and wet
pattern develops in the long term period. Elongated surface high
pressure will stretch across the Great Lakes into the Ohio Valley
today through Friday providing mainly clear, dry and cool
conditions. Highs today will reach the 40s most areas while lows
tonight once again drop back into the 20s with good radiational
cooling. Not much change on Friday with high pressure beginning to
slide east as next wave approaches. Highs should reach the mid to
upper 40s.


.LONG TERM...(Friday Night through Wednesday)
Issued at 445 AM EDT Thu Mar 22 2018

Two systems of concern in the long term with heavy wet snow possible
late Friday night into Saturday. Second system middle of next week
could bring locally heavy rainfall back to the region along with
warmer temperatures.

Pacific wave currently bringing deep moisture and heavy rainfall to
CA today will cross the Rockies and induce lee side cyclogenesis on
Friday. Building warmth across the southern Plains will be drawn
northward leading to a tightening baroclinic zone and development of
a strong warm front ahead of developing surface low. Strong system
relative isentropic lift and moisture advection expected to develop
a large area of pcpn along and north of warm front Friday night into
Saturday. This boundary will likely reach into central Indiana as
the sfc low moves east to western IL before diving southeast and
weakening on Saturday. This southeast shift being steered by
stubborn high pressure that remains parked over the cold Great Lakes
with a stout dry low level easterly flow over most of our area.

Pcpn associated with warm front should reach far southern counties
late Friday night before encountering drier air. This should provide
another sharp gradient and cutoff to pcpn which is problematic for
snowfall forecast and amounts. Models typically throw too much QPF
into the cold and dry sector so expect a much sharper gradient to
PoPs and QPF than currently forecast. However, difficult to
ascertain where this boundary will actually setup given minor model
differences so must respect this uncertainty with lower pops.

Combination of blend and WPC suggest our far southern row of
counties will see the heaviest pcpn, which should fall mainly as
snow given strong dynamical and evaporative cooling processes. QPF
amounts rather impressive with a half to just over three quarters of
an inch progged by blends and WPC in our far south to southwest.
Another difficulty will be accessing impacts from potential snowfall
amounts of 3 to as much as 7 inches on the high side given warm late
March sun angle and sfc temps Saturday rising above freezing. Roads
should be more of a wet slush with snow liquid ratios around 10:1
Fri night and closer to 8:1 later Saturday morning and afternoon
before pcpn ends. Thinking this will mainly be an advisory event for
our area with high compaction and low impacts but consensus among
neighbors was to go with a watch given upside potential, especially
in our extreme south and points just south of our area.

Second system of concern will be Mon night-Wed time frame. Closed
upper low looks to develop over the southwest CONUS with deep
Pacific moisture feed likely ahead of it spreading into the Midwest
and Great Lakes region. Surface front will become parallel to upper
flow from southwest to northeast and models showing several waves
along boundary with some heavy rainfall potential. Still a lot of
uncertainty on where the sfc front will actually set up and timing
of the waves. However, medium range models all point to potential
heavy rainfall event somewhere across the Midwest or Ohio Valley and
this will need to be watched closely in this favored waning but
still active La Nina pattern. This should also finally provide some
early Spring warmth to the region with temperatures trending near
and above normal next week.


.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 113 AM EDT Thu Mar 22 2018

VFR conditions are expected at both KFWA/KSBN through the TAF


IN...Winter Storm Watch from late Friday night through Saturday
     afternoon for INZ013-020-022-023-032>034.

LM...Small Craft Advisory until 8 AM EDT this morning for LMZ043-046.



SHORT TERM...Lashley
LONG TERM...Lashley

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