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Area forecast discussion 
National Weather Service northern Indiana
600 am EDT sun Apr 20 2014

issued at 415 am EDT sun Apr 20 2014

Strong high pressure will begin to shift east today but will still
support mostly sunny skies and dry conditions. Southerly winds
behind this high pressure will bring temperatures in the low to
middle 70s today with overnight lows in the upper 40s to around 50.
There is a chance of rain late Monday as a cold front sweeps
through the region.


Short term...(today and tonight)
issued at 415 am EDT sun Apr 20 2014

Nearly picturesque Spring day on tap for the southern Great Lakes
today. Upstream frontal boundary will remain nearly stationary to
our north and west with dry/stable low level ridge maintaining a
sizable influence on our area. Only detrimental aspect of the
forecast will be a fair amount of high clouds being advected from
the west. Upstream cirrus deck looks rather thin/translucent on
latest infrared imagery though and will therefore maintain a mostly
sunny forecast. Loosely filtered insolation...veering low level
winds...and a weaker subsidence inversion will allow for slightly
better mixing depths and a much warmer day. May not be able to mix
all the way to 850mb but 875-900mb temperatures are still expected to
rise into the 11-12c range. This yields afternoon highs in the low
to middle 70s. Inherited high temperature forecast is already fairly
aggressive with general middle 70s. High sun angle...equivalent to a
middle August day...and very dry lower levels have allowed for deeper
than expected mixing and warmer afternoon temperatures during several of
the past few days. Will therefore continue to lean on the warm
side of guidance with minimal changes to inherited grids but will
also have to monitor diurnal temperature trends through the day.
Overnight lows also take a corresponding jump higher given warmer
starting temperatures this evening. Increasing clouds and weak warm air advection may
limit diurnal losses somewhat but still expect most areas to drop
into the upper 40s to lower 50s due to only light southerly winds
at the surface and late arrival of high-based cloud cover.


Long term...(monday through saturday)
issued at 415 am EDT sun Apr 20 2014

A bit of a roller coaster ride in the long term with respect to
temperatures. No significant weather events expected but a couple
short waves will bring a chance for showers with a chance for a few
thunderstorms as well. Bulk of forecast in good shape and only some
minor adjustments made with this package.

Pv anomaly moving through the Great Lakes on Monday will help drive
a cold front across the local area Monday night. Modest moisture
flux along boundary with weak upper support but models all agree on
generating at least some light quantitative precipitation forecast with this system as precipitable waters pool to
around an inch and maximum 0-3km Theta-E increases to 320k. Still expect
quarter inch or less and some locations likely only a few

Cooler air returns in wake of this wave for Tuesday. Lake shadow and
marine layer to move well inland during the day keeping temperatures down
despite subsidence and afternoon insolation. Latest blended guidance
close to going forecast with temperatures remaining in 40s near Lake
Michigan...middle 50s central and maybe reaching 60 in far south and
southeast. High pressure will settle over the County Warning Area Tuesday night making
for ideal radiational cooling. Very dry profiles and light winds
suggest temperatures will radiate quickly Tuesday night. Kept temperatures in the 30
to 34 degree range for now but concerned for some upper 20s across
northern areas. With growing season not fully underway...growing
degree days generally under 75 for season so far...we will not be
headlining any frost or freezes. However...we will continue to
highlight in severe weather potential statement for now and include frost possibility in grids.

Return flow develops Wednesday night as low pressure in plains organizes.
Best forcing west and north of area so have opted to keep this
period dry despite some light quantitative precipitation forecast being generated by medium range
models and low pop from allblend. Thursday could also remain dry
with negatively tilted system well west of the area.
However...height falls with increasing moisture Thursday afternoon
warrant the continuation of low chance probability of precipitation. Models in reasonable
agreement with best chances for rain Thursday night as Gulf is briefly
tapped and precipitable waters increase to over an inch with Theta-E surge and
occluded front moving north. Closed system will then drift over the
western Great Lakes Friday keeping a low chance for showers in
forecast. Another chance for cooler air on Saturday in wake of this
system but models have shown a trend toward some modification of air
compared to previous runs.


Aviation...(for the 12z tafs through 12z Monday morning)
issued at 600 am EDT sun Apr 20 2014

VFR conditions will remain in place given persistent midlevel
ridging and a very dry and stable airmass. Middle/high clouds will
gradually increase through tonight as the next system approaches
but any chance of rain or lower ceilings remains well past 12z


Iwx watches/warnings/advisories...


short term...agd
long term...Lashley

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