Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
720 PM EDT Friday Oct 24 2014
issued at 1106 am EDT Friday Oct 24 2014
While conditions are expected to be dry...skies today and tonight
will remain partly to mostly cloudy. Afternoon highs will reach
into the low to middle 60s in most areas. Lows tonight will be in the
upper 40s. Otherwise...a warm and pleasant weekend is in store.
Skies will be partly to mostly clear...with highs in the 60s and
Short term...(this evening through saturday)
issued at 357 PM EDT Friday Oct 24 2014
Similar to last night...another weak short wave will move through
the region overnight. 12z models do show a bit deeper column of
moisture tonight but satellite this afternoon showing little in the
way of synoptic clouds upstream associated with this feature.
However...there is still quite a bit of low level stratus and fog
across the Midwest left over from this morning. Feeling is that 12z
models may have picked up on this low level moisture from 12z regional
radiosonde observations...which otherwise are quite dry....and are projecting it
downstream with synoptic wave. Several models came in with a few
hundredths quantitative precipitation forecast where previous forecasts had little if any. Nam12 and
gfs40 do show a decent short wave and vorticity maximum but much lower than
the typical 500mb level. A nice reflection is seen around 850-700mb
along with some system relative isentropic lift on the 300k surface
in tandem with the aforementioned moisture column. With a
lack of support currently on satellite and radar and light nature
expected...have opted to stick with the silent 10 to 14 percent
probability of precipitation. However...will add chance for sprinkles as even last nights
system over performed with a few areas seeing a few hundredths of
an inch. Lows tonight with clouds increasing will range from middle
40s east to lower 50s west.
Expect main surface front with wind shift to move through middle
morning to early afternoon Saturday with clearing in its wake
through the afternoon hours. Highs will generally be in the low to
middle 60s with slightly cooler air infiltrating the north in the
afternoon once flow comes around off the lake.
Long term...(saturday night through friday)
issued at 357 PM EDT Friday Oct 24 2014
A strong upper level trough will move across the Continental U.S. Early next week
and is expected to bring a good chance for rain to the forecast area
beginning Monday night. The GFS and European model (ecmwf) appear to have a good
handle on the initialization and early verification of the track of
this system that this afternoon was well off the West Coast of North
America. The GFS and European model (ecmwf) through Tuesday also have had reasonable
run to run consistency...so have continued high chance or likely
rain chances Tuesday. Have added a slight chance for thunder Tuesday
given vigorous upper air support...sufficient moisture and adequate
low level forcing associated with the front. Ahead of this system...
raised highs over northeast areas Monday...with afternoon temperatures
reaching 72f to 76f over all land areas except very close to Lake
Michigan. Otherwise...much cooler air will spread into the area late
in the week. The GFS and European model (ecmwf) diverge significantly...with the GFS
now colder than the European model (ecmwf) at 850 mb Saturday morning with a -10c.
Therefore...trended highs down a little Friday in line with the
latest European model (ecmwf) and GFS long term guidance.
Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 720 PM EDT Friday Oct 24 2014
Modest shortwave moving across the northern Great Lakes tonight
will send a weak cold front across the area early tomorrow
morning. Best forcing remains well to the north but could be
enough low level convergence and moisture advection ahead of the
front to allow for a period of low stratus. This is supported by
latest upstream observation and model guidance. Left in a roughly 8 hour
window of fuel alternate conditions but actual duration will
likely be shorter and can be further refined with the 06z taf
issuance. Best chances for fuel alternate conditions appear to be
around 11-13z. Could be some patchy br during this time as well.
Strong dry air advection will scour out any residual cloud cover
by tomorrow afternoon.
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