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Area forecast discussion 
National Weather Service northern Indiana
556 am EDT Sat Apr 18 2015

issued at 330 am EDT Sat Apr 18 2015

High pressure will bring another quiet and warm day today. Expect
highs in the middle to upper 70s with lows tonight in the upper 40s
to lower 50s. Widespread rain and a few embedded thunderstorms are
expected on Sunday as a low pressure system lifts into the Great


Short term...(today and tonight)
issued at 330 am EDT Sat Apr 18 2015

One more benign weather day on tap before rain returns for the
latter half of the weekend. Confluence aloft and Stout midlevel
ridging ahead of slowly approaching cutoff low will maintain dry
conditions. GFS cp scheme continues to ignite precipitation this
afternoon...tied to subtle low level convergence along weak backdoor
cold front sliding through the southern Great Lakes in a very
marginally unstable environment. 100-200 j/kg SBCAPE is predicated
on surface dewpoints in the middle 50s...which may be difficult given
slow Greenup and another day of very deep mixing. Steep low level
lapse rates and weak convergence would suggest at least some nonzero
threat for an isolated sprinkle but all of the nearby 00z upper air
soundings show an incredibly dry airmass in place. Will therefore
continue with silent probability of precipitation at or below 10 percent.

Maximum temperatures will once again be the primary concern for today. Forecast
soundings indicate another day of very deep or above
800mb. Will probably be a bit more cloud cover today but thermal
profiles are also a tad least in our southwest half.
Yesterday's highs were above most guidance and expect similar
results today. Inherited forecast reflects this well and only minor
edits made. Did lower forecast just a touch given approaching
backdoor front. Still expect highs in the upper 70s for most
locations but cooler conditions possible in our northeast where
earlier arrival of east-northeast winds and closer proximity to very cold
waters of lakes Huron and Erie may cap afternoon highs a bit. Cool
east-northeast surface winds should allow for another night in the upper 40s
despite increasing gradient and cloud cover ahead of approaching
system. No rain expected prior to 12z.


Long term...(sunday through friday)
issued at 330 am EDT Sat Apr 18 2015

Devil lies in the details of phasing northern/southern stream energy early in
the period. Two pronged piecemeal ejection of potent southern stream system expected
west/primary wave lifting up across the area Sun afternoon and secondary lt
Sun night/Monday am. Thus while 00z guidance is similar aloft...highres
solution space is somewhat disparate otrws especially west/surface cyclone
lifting up into the area on lt Sunday although good clustering does
exist in spectral guidance. Consensus surface low track up through northwest in
would portent heavier rainfall through far western zones while means of
highres guidance would back this into eastern/NE Illinois. Regardless given
expected northward advection of Gomex sourced moisture plume widespread rain will lift
up across the area Sun afternoon. Thunder threat again looks exceedingly
poor west/deplorable lapse rates through a deep/saturated column yet
will keep west/isolated ts mention for sake of continuity.

After that...cold core dominant northern stream system to cutoff across the northern
lakes and slowly meander eastward into southeast Canada by next weekend. Dry
subsident middle level follow expected to persist through the remainder of the
period west/much below normal temperatures expected and a threat for frost/freeze
conditions in later periods.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 556 am EDT Sat Apr 18 2015

High pressure will maintain VFR conditions through the period.
Deep mixing and dry boundary layer will keep ceiling heights well
above 3 kft today. Easterly wind will increase tonight as low
pressure approaches but any rain or reduction in flight category
will hold off until after 12z Sunday.


Iwx watches/warnings/advisories...


short term...agd
long term...T

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