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Area forecast discussion 
National Weather Service northern Indiana
322 am EDT Sat Aug 1 2015

Synopsis...
issued at 320 am EDT Sat Aug 1 2015

Expect mostly sunny skies through early afternoon...then
increasing clouds and a chance of showers and thunderstorms this
evening. Highs will range from the upper 70s near Lake Michigan to
the middle 80s inland.

&&

Short term...(today and tonight)
issued at 320 am EDT Sat Aug 1 2015

Another difficult short term period on tap. Another in a
series of upper disturbances over southwestern Ontario was noted this morning
rotating east/southeastward through based of upper low centered over James Bay west/some
decaying convn along the North Shore of lake supply. However unlike yesterday sig
scouring of ll Theta-E ridging had occurred which by all short term
guidance accounts will take some time to recover. That said mean
troughing associated/west James Bay upper low expected to flatten this period as southwestern
Ontario disturbance wraps eastward. Surface trough in association/west this ftr expected
to pass through the southern/western lakes this evening west/robust renewed ll
Theta-E plume folding eastward into the western County Warning Area toward 00z and progressing
into Ohio by lt evening. Best overlap of moisture/forcing and frontal timing
warrants an appreciable bump to probability of precipitation this evening western half followed
by a tail off west/E/se extent by lt evening. Otrws seasonable temperatures
expected again through the period west/enlarged diurnal spreads fvrd again.

&&

Long term...(sunday through friday)
issued at 320 am EDT Sat Aug 1 2015

Northwest flow regime aloft will persist under a Hudson Bay negative
height anomaly that will drift east-southeast into southeast Canada. The result
will be temperatures trending cooler than normal and several opportunities
for rain/storms as a series of middle level impulses propagate through.

The main focus Sunday into early Monday will be convective
trends/chances in advance of a cold front modeled to translate
through Sunday night/early Monday. The associated sharp middle level
shortwave/height falls into the Great Lakes will aid in ramping of
pre-frontal low level jet into the lower lakes. The resulting
increase in moisture/instability will prime the local area for
convection. However...chances during the day Sunday appear
low...with morning/early afternoon activity into northwest zones
dependent on timing of a weak lead shortwave and survival of
Saturday night's upstream convection into the lower lakes. Better
chances appear to be northwest in an area of more focused moisture
convergence/isentropic ascent.

Growing surface based instability within warm sector expected by Sunday
afternoon/early evening. However...held with low probability of precipitation given
increased capping/eml overspread with region caught in between upper
waves. Cold frontal passage looks good for a round of rain/storms
Sunday night...but held off on increasing into the likely category
given lingering model timing/strength differences. Will need to
monitor the potential for organization into a mesoscale convective system (wind threat)
given strong 0-3 km flow/shear and lingering moderate instability
(thanks to steepening middle level lapse rates and middle/upper 60s surface
dewpoints).

The aforementioned front will focus/suppress south in the vicinity
of the Ohio/middle MS valleys for much of next week in response to
southern drift of Hudson Bay low. Northerly to easterly flow at the
surface will support below normal temperatures and mainly dry conditions across
at least the northern half of the forecast area. Lower confidence
for areas along/south of the Highway 30 corridor regarding rain/embedded
thunder chances Tuesday through Wednesday night given close proximity
to active frontal slope.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 320 am EDT Sat Aug 1 2015

VFR conds expected again this period. However another in a series
of disturbances embedded within northwest follow aloft dropping out of SW
Ontario will send a surface trough across the terminals this evening. Btr
chance for a brief period of thunderstorms and rain in vicinity of ksbn this evening yet given
conflicting near term guidance signals prefer to wait for a more
consistent signal in later guidance before taking a Stab at inclusion in
taf.

&&

Iwx watches/warnings/advisories...
in...none.
Michigan...none.
Ohio...none.
Lm...none.
&&

$$

Synopsis...T
short term...T
long term...steinwedel
aviation...T



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