Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
400 PM EDT Sat Mar 15 2014
issued at 1155 am EDT Sat Mar 15 2014
Cooler temperatures will continue through the weekend as colder air
settles back into the region. Look for highs in the upper 30s north
to upper 40s south. Lows tonight will range from the middle teens
north to lower 20s south. Light snow is possible across across the
western half of the area early tonight...but little to no
accumulation is expected. Highs Sunday will struggle to reach the
upper 20s and low 30s.
Short term...(this evening through sunday)
issued at 358 PM EDT Sat Mar 15 2014
A cold front was moving south across the forecast area with an area
of Post frontal clouds lingering over northern Indiana. Upper level jet
dynamics were associated with cloud cover over southern WI into northern Illinois.
Kept a small chance for light snow over western areas early
tonight. Otherwise...very cold air will continue to spread south
into the forecast area tonight. The pressure gradient will tighten
up significantly tonight as surface high pressure builds in from the
north. Cloud cover and some lingering snow cover will keep highs
Sunday near record cold temperatures of 20 to 25. Rejected the NAM/met that
has had a significant cold bias in lieu of the warmer mav and ec.
Long term...(sunday night through saturday)
issued at 358 PM EDT Sat Mar 15 2014
Arctic high over the upper Great Lakes Sunday night will move east to the
lower Great Lakes by Monday morning with a ridge extending back west-southwest across
our County Warning Area. Skies should be clear most of the night with perhaps some
cirrus moving in from the northwest late. This will set up good radiational
cooling... especially across northern portions of the County Warning Area where some snow
cover should remain. Forecast lows near colder European model (ecmwf) MOS ranging from
the single digits north-NE to the teens S-SW.
High will continue to move away from the area Monday with weak east-southeast surface
winds and weak 850 mb warm air advection. A weak shortwave will move through the upper Great Lakes
during the day resulting in some high clouds... however expect
sufficient insolation/diurnal heating to allow temperatures to reach warmer
end of guidance (gfs ensemble MOS and European model (ecmwf) mos) with highs ranging
from the l30s north to the l40s south.
Although weak low level warm air advection will continue Monday night... little change in
weak pressure gradient and little cloudiness should provide another
night of good radiational cooling. Again leaned toward colder European model (ecmwf)
MOS with lows forecast to range from the teens NE to the m20s south.
For the extended forecast... medium range models in fairly good
agreement that a rather strong low pressure system will move east-NE
from the plains Tuesday across the upper Great Lakes Wednesday... and into Quebec by
Thursday. Still some significant timing differences with European model (ecmwf) about 6hrs
slower than GFS/Gem with frontal passage in our area. Models suggest showers
with this system will be with the frontal passage and in the cold air advection/wrap
around... so given the timing differences will continue with just chance
probability of precipitation for both Tuesday night and Wednesday. In either case... Gulf moisture tap
forecast to be rather weak... so rain amounts in our area from this
system should be light. Decent warmup expected ahead of this system
Tuesday as low level gradient mixing strengthens with mostly sunny
skies... highs should range from the u40s north to the u50s south.
Followed model blend for temperatures Tuesday ngt/Wed... but considerable
uncertainty remains due to continued questionable timing of frontal passage.
High pressure ridge expected to build into the area Thursday providing
fair weather with cooler Post cold front temperatures. European model (ecmwf) remains a little slower
with the ridge passage Thursday-Thursday night but close enough that at least a
period of good radiational cooling expected Thursday night.
Next shortwave to impact the area which was located over the western
Pacific near 50n 165e today... is forecast similarly by GFS/European model (ecmwf) to
move through our area Friday bringing another chance of precipitation... with
dry/colder weather in its wake Saturday as high pressure builds in from
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 127 am EDT Sat Mar 15 2014
Initial cold front has cleared taf sites with skies becoming
mostly clear. Latest satellite and surface observation show an area of
stratocumulus has developed over Lake Michigan and is moving into
ksbn at issuance and toward kfwa. This area is currently
developing and expanding so duration and extent still in question
for next few hours. Have included a period of MVFR at ksbn given
heights around 3kft but kept kfwa VFR for now with erosion of
bases as this area moves east. Otherwise middle and high clouds
develop Saturday as another weak front sags through the area.
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