Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service northern Indiana
828 PM EDT Wednesday Apr 16 2014

issued at 536 PM EDT Wednesday Apr 16 2014

Dry conditions will continue tonight and through most of tomorrow
with moderating temperatures as highs reach near 60 degrees
Thursday. A frontal boundary will move across the region late
Thursday night and Friday bringing increasing chances for rain
showers. The weekend should be fairly nice with temperatures
gradually warming to near 70 degrees by Sunday.


issued at 820 PM EDT Wednesday Apr 16 2014

Warm advection to continue tonight with scattered-broken high level clouds
overspreading the area. Despite dry low levels...strength of warm
advection and modest gradient in place may tend to keep lows a few
degrees warmer than forecast. May make some minor tweaks to mins
over the next hour...but no significant changes expected to the
forecast this evening.


Short term...(this evening through thursday)
issued at 312 PM EDT Wednesday Apr 16 2014

Water vapor loop showing a potent vorticity maximum over eastern South Dakota this afternoon
while a very dry airmass was spreading across the southern U.S. And
northern Gulf of Mexico. South Dakota vorticity expected to shear out as it lifts NE
across Lake Superior while several weak trailing shortwaves move east
from The Rockies and carve out a fairly deep middle level trough from
Minnesota-NE Texas by Thursday evening. At the sfc, low pressure over western Iowa also
expected to weaken as it lifts NE to Eastern Lake Superior with
trailing cold front across northern Illinois to NE Texas by Thursday evening. Strongest
forcing associated with the lead shortwave will pass by to our northwest
tonight while main area of forcing along/ahead of approaching middle level
trough and surface cold front should remain west of our County Warning Area through Thursday evening.
Initially dry conditions across the Gulf will result in weak
moisture return ahead of the cold front. Thus... dry conditions should
continue through the short term period... but do expect
considerable high cloudiness across the northwest 1/2 of the County Warning Area. Decent
southeast gradient winds should persist tonight and along with weak warm air advection
prevent temperatures from falling much with lows expected to range from
the l30s east to the m30s west. Sufficient gradient/insolation
expected Thursday for boundary layer mixing up through 850 mb resulting in
highs in the l60s over most of the area.


Long term...(thursday night through wednesday)
issued at 312 PM EDT Wednesday Apr 16 2014

All in all a generally dry period in store with only 2 limited
chances for rainfall as Gulf of Mexico remains cut off until closer
to the end of the period.

Seasonable temperatures are expected to start out the first few days. Upper
level wave will pass well northwest of the region with a moisture starved cold
front (850 mb Theta-E barely touches 300 k and precipitable waters 0.75 or less)
passing across the area Thursday night into Friday. Despite this...looks
like sufficient forcing will exist to force at least scattered
showers...warranting continued middle to upper chance range probability of precipitation with
highest NE. The front will bring little cold air with it this far
south with 850 mb temperatures barely touching +2 c Friday night. Quick
rebound in temperatures expected as closed low over the SW allows for
increasing heights and temperatures heading above normal into the 60s. Have
stayed conservative but could see some 70s by Sunday just ahead of
the ejecting...but dampening wave. Another chance for showers will
arrive late Sunday into Monday as this wave passes just to the south
of the area with better moisture (theta-E approaching 320 k) warranting
again middle-high chance probability of precipitation.

Focus will shift to large trough that will dig into the SW states
towards the end of the period. This should cause a strong increase
in heights and potential return to much above normal temperatures. In
addition...some models indicate Gulf would open up which could
suggest increasing chances for storms as pieces of energy eject.
Lots of time to monitor this...but trend towards warmer weather
definitely seems to be shaping up.


Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 820 PM EDT Wednesday Apr 16 2014

VFR conditions to persist this period with little in the way of
significant moisture transport until late in the period. Southeast
low level flow has kept a dry low level air mass in place across
the region...with just some high level cloudiness anticipated
through tonight. Modest gradient associated with surface low pressure
across western Iowa will result in maintenance of south winds 10
to 15 knots...with loss of higher gusts next hour or two. Narrow
low level moisture axis may promote a bit more in the way of
diurnal VFR scattered cumulus Thursday afternoon. The low is expected to fill
on Thursday which should keep gusts in the 15 to 20 knot range in
the afternoon.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory until noon EDT Thursday for lmz043-046.



short term...jt
long term...Fisher

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