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Area forecast discussion 
National Weather Service northern Indiana
716 PM EDT Tuesday Sep 2 2014

issued at 716 PM EDT Tuesday Sep 2 2014

Isolated showers will diminish by middle evening as drier air slowly
filters into the region. This will allow lows to drop into the 50s
tonight with areas of fog developing after midnight. Once the fog
Burns off on Wednesday a beautiful early September day will be in
store with highs in the middle 80s and lower humidities.


issued at 656 PM EDT Tuesday Sep 2 2014

Forecast still on track next couple of hours as several boundaries
(outflow and lake breeze) were drifting south across north Indiana and
Northwest Ohio. Isolated showers have popped here and there and even a
stray lightning strike a few hours ago. Trends should continue
downward with loss of heating and eventual translation of
boundaries out of the area.


Short term...(this evening through wednesday)
issued at 344 PM EDT Tuesday Sep 2 2014

Infiltration of drier air into the region has been slow this
afternoon...with ample boundary layer moisture amid washed out
surface boundary across the forecast area. Low clouds have been slow
to mix out through early afternoon but latest Sat trends showing
more scattered low level cloud layer...especially northwest. Isolated showers
currently noted on radar across northwest/NC in...given ample boundary
layer moisture...weak surface convergence and surface heating yielding very
modest sb convective available potential energy up to 1000 j/kg across the region. Hrrr and even
nam12 hinting at isolated shower activity spreading east across the
forecast area through sunset. Therefore have kept an isolated shower
mention through 00z in the forecast. Low confidence for thunder at this
time given lack of forcing and weak middle level lapse rates.

As ridging builds eastward into the overnight hours...clearing skies
and dry conditions expected. With slackening gradient and low level
moisture...especially southeast west/ the precipitation over the past 24 hours...fog
development looks likely late in the overnight into daybreak
Wednesday. Kept previous forecast in tact with areas of fog mention from
09-12z. Low confidence with the possibility of dense fog at this
time...given low level dry advection and extensive cirrus shield
noted across the southwest half of the forecast area this afternoon.
If cloud cover is quick to diminish tonight...W/ lack of any
convective debris...then dense fog chances would increase toward
tomorrow morning...especially southeast. Will monitor trends through the
evening and will update as necessary.

Ridging builds east of the area through the day on Wednesday...with
mostly sunny skies and fair conditions. Kept high temperatures slightly
below mav...although upward adjustment may be needed in the next
forecast with warm air advection into the area by the afternoon hours on the western
periphery of the ridge.


Long term...(wednesday night through tuesday)
issued at 344 PM EDT Tuesday Sep 2 2014

The GFS and European model (ecmwf) have appeared to initialize the upstream short
wave well and also seem have a reasonable track with this system
across the Continental U.S. This week. The European model (ecmwf) and GFS have also shown good
consistency from run to run with this system the past several runs.
Low level Theta-E and moisture flux will increase rapidly Wednesday
night...especially north and northwest of the area. Have added a
small chance for thunderstorms overnight Wednesday night on the
leading edge of this Theta-E advection over far northwest areas...
especially Berrien and LaPorte County. Kept Thursday dry as the
primary low level forcing shifts north of the area and as a low
level inversion increases at the base of a weak to moderate elevated
mixed layer. The GFS mav/mex temperatures have been consistent at
generally 5 to 10 degrees above normal for Thursday and Friday and
appear on track with 850 mb temperatures approaching 20c.
Thunderstorm chances look best overnight Thursday night through
Friday night as a cold front approaches. Given the timing of the
front and substantial instability by late Thursday and Friday
afternoon/early evening with convective available potential energy as high as 2000 to 3000
j/kg...concern for an upstream convective complex to drop southeast
or south into the forecast area as rich Theta-E spreads over the
area. Expanded thunderstorm chances Thursday night in this regard.
Otherwise...kept storm chances Friday and Friday night. Otherwise...
cooler and drier conditions can be expected for the weekend into
next week with highs in the 70s through Tuesday.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 656 PM EDT Tuesday Sep 2 2014

Final surge of drier air...being accompanied by several weak
boundaries...will shift through kfwa over the next hour or so.
Can't rule out a stray shower but coverage/chance of impact so
small not worthy of a taf mention. Focus then shifts to fog
potential later tonight. Have left previous tafs intact as better
chance for fog looks to reside at kfwa where recent rainfall will
leave more residual moisture as well as slower arrival of drier air in
this area. Little more than high clouds to be seen on Wednesday.


Iwx watches/warnings/advisories...



long term...skipper

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