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Area forecast discussion 
National Weather Service northern Indiana
1244 PM EDT Monday Oct 20 2014

issued at 414 am EDT Monday Oct 20 2014

A cold front will move across the area today...bringing a chance
of showers and possibly a few thunderstorms mainly this afternoon
to eastern Indiana...northwestern Ohio and eastern lower Michigan.
Afternoon highs are expected to reach the upper 50s to lower 60s.
Cooler air will move back in for tonight into Tuesday. Lows will
be in the middle 40s with highs Tuesday in the 50s.


issued at 900 am EDT Monday Oct 20 2014

Strong DCVA and steepening lapse rates associated with a potent
shortwave now dropping into northern Illinois has been enough to generate a
broken line of showers and isolated thunder across Northwest Indiana/SW lower
Michigan this morning. This forcing along the system cold front will
translate east into central zones middle-late morning where probability of precipitation were
increased a bit and a slight chance of thunder was added. Forecast on
track otherwise with only minor tweaks made.


Short term...(today and tonight)
issued at 414 am EDT Monday Oct 20 2014

Nose of warm air advection was working across the forecast area with
a band of light showers currently extending from Hillsdale SW to
near Syracuse. Overall coverage has decreased over the past couple
of hours as it encounters increasingly drier air. Expect the line to
shift east and exit by 12z.

Focus then shifts to cold front located from western Wisconsin to
central Iowa as of 8z. Water vapor loops shows a rather Stout short
wave dropping southeast with timing of this feature and the front
rather favorable for development of showers late am in the west into
the afternoon hours east. Quick surge of moisture will move NE into
mainly eastern counties as low level flow ramps up somewhat in
response to the wave. Several high res models indicate increasingly
unstable conditions in eastern areas with surface based lifted indice's 0 to -2
c and cape in the 200 to as high as 500 j/kg range. Also core of
cold upper level temperatures (500 mb -20 to -22 c) will also enhance lapse
rates. Given favorable timing and the noted parameters...will add
slight chance mention of thunder...also matching swody1 outlook. With
cold air aloft...can't rule out some small hail with the stronger
cells. Clouds were clearing across the west which should allow a
period of heating and temperatures climbing near or into the 60s mainly

Colder air quickly arrives in lower levels later this afternoon into
tonight as wave departs and flow becomes northwest and then north overnight.
Lake temperatures were in the middle teens with Delta t's expected to
peak out around 14 c with equilibrium levels 5000 to 6000 feet.
Previous grids already captures potential for lake effect rain
showers in far western areas late afternoon and increasing somewhat
tonight. Lows will drop into the 40s.


Long term...(tuesday through sunday)
issued at 414 am EDT Monday Oct 20 2014

Main forecast items to address for the long term will be lingering
lake effect rain showers to begin the period...along with low
probabilities of additional synoptically forced showers across
mainly eastern portions of the forecast area Tuesday.

On Tuesday morning...a 100 knot upper speed maximum will be dropping
southward along western periphery of eastern Great Lakes upper low.
Upper vorticity maximum associated with this shear zone will dig across the
Ohio Valley during the day. Track of this vorticity maximum should favor far
eastern locations for additional synoptic forcing while synoptic
scale subsidence becomes established across western Great Lakes.
Moderate low level Delta temperatures and Steep Lake induced low level
lapse rates should support at least chance of lake effect rain
showers across the far northwest...although increasing subsidence
and drying middle level profiles after 12z should tend to limit this
potential. Slight veering of low level wind profiles in association
with secondary surface trough accompanying this short wave could also
take focus for any additional light lake effect rain showers just
west of iwx County Warning Area by Tuesday afternoon. Reinforcing low level cold
advection push on Tuesday should provide for another cool day...with
main uncertainties at this time regarding extent of cloud cover into
the afternoon. Middle level subsidence should tend to sharpen low level
inversion and with large scale cyclonic flow persisting...expecting
low clouds to win out. Thus...have gone toward the cool side of
guidance for maximum temperatures Tuesday...generally in the lower 50s most
locations although this may be a bit too warm in spots.

Lake effect clouds should diminish Tuesday evening and shift west of
the area with more veered low level flow. Elsewhere...expecting
lingering stratocu to scatter or clear out setting up better
radiational cooling conditions. Best radiational cooling conditions
should occur across the west where lows should drop well into the

Remainder of the long term period looks to be quiet as large scale
upper ridging builds into the western Great Lakes. One notable trend
in guidance over past several runs has been toward a Delaware-emphasis on
southern stream cut-off and a more consolidated upper trough
approaching the western Great Lakes Thursday. Latest trends would
support a steadier eastward progression of narrow low level moisture
axis into the region some time in the Thursday-early Friday period.
With poor run to run continuity for this period...and models tending
to struggle with these systems in relatively weaker steering
flow...have held off on any probability of precipitation for this period but may eventually
need to add some mention in the Thursday/Friday timeframe.

In terms of temperatures...upper system closing off across eastern
Continental U.S. Through middle week will limit extent of any moderating
temperature trend through Thursday. Prospects for more notable
moderation should occur for the first part of the weekend as middle
level height rises push into the region. Some indications that
southern Canadian short wave will drive another cool front south
later in the weekend...but confidence in timing and magnitude of any
cooling at this forecast distance in this pattern remains low.
Current indications would suggest stronger low level cold air advection remaining
north/northeast of the area however.


Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1244 PM EDT Monday Oct 20 2014

Showers/isolated thunder with potent vorticity maximum/cold front should push
east of kfwa by or just shortly after taf issuance leaving mainly
dry conditions in strengthening northerly flow thereafter. The
only exception may be at ksbn where a Few Lake effect showers may
develop this evening into early the overnight before shifting west
of the terminal. Variable MVFR-VFR ceilings should give way to a solid
Post-frontal MVFR strato cumulus deck near 2 kft by later this
afternoon-tonight in lingering moist cyclonic flow on the backside
of an amplifying upper trough. Otherwise...expect west-southwest winds at
issuance to veer northerly by tonight.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory from 8 PM this evening to 5 am EDT
Wednesday for lmz043-046.



short term...Fisher
long term...marsili

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