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Area forecast discussion 
National Weather Service northern Indiana
243 am EDT Friday Apr 25 2014

issued at 210 am EDT Friday Apr 25 2014

A low pressure system will race northeast across the region today.
Showers associated with the low will end from west to east today
as the low moves northeast. Highs today will range from the upper
50s over lower Michigan and Northern Ohio to the lower 70s over
northeast Illinois. Some additional light showers are possible
tonight with a weak upper level system. Lows should be in the 40s.


Short term...(this evening through friday)
issued at 352 PM EDT Thursday Apr 24 2014

Primary focus on approach of vigorous upstream shortwave trough
embedded within overall negative tilted longwave pattern.
Attendant western MO surface low to track east-northeastward into central in by
12 UTC Friday and into Northern Ohio at 18 UTC. Strong moisture flux
convergence given advection of 5 plus g/kg 8-500 mb layer as middle
tropospheric flow of 40-50kts across southern MO moves up Ohio River
valley basin. Have relegated slight thunderstorms and rain mention to far southern/southeastern
County Warning Area maximized hodo with deep layer forced parcel ascent amplified
by arrival of 80-100m/12hr along with northern extent of MUCAPE
plume/apex at or below 200 j/kg toward daybreak. Some slight slowing of
frontal system afforded given negative tilt/maturation to occlusion.
Maintain warm temperatures on Friday as Post frontal thermal trough rather
narrow... lack of strong upstream surface ridge and potential strong
afternoon insolation.


Long term...(friday night through thursday)
issued at 352 PM EDT Thursday Apr 24 2014

Frontal boundary should be clear of the area at the start of the
period with a dry start to Friday evening. A handful of models still
bring a weak disturbance across the County Warning Area with light quantitative precipitation forecast. Not overly
impressed but given location of front just south of the area can't
discount entirely. Have went with slight chance probability of precipitation only late Friday night.

Otherwise focus will shift to large upper low that will slowly make
its presence known across the region towards middle week. A massive
struggle should take place in moisture return with limited flow from the
Gulf until the low draws closer. European model (ecmwf) closest to this thought
process with other medium range models trying to bring precipitation in
faster. As a result have increased probability of precipitation far SW starting Sun night and
slowly expanding NE through Monday night and Tuesday when upper low
begins to move overhead. From this point forwards is where it
becomes somewhat more interesting. As noted above...moisture from the
Gulf will begin to come north and get wrapped on the east side of
the low. Hints of dewpoints into the 50s exist with guidance numbers
pointing toward potential highs in the 60s to maybe near 70. To
complicate is typical with these Spring cut off
lows...pool of cold 500 mb temperatures will be approaching...possibly
pushing -20 c depending on model of choice. If pocket of limited
clearing can occur...very steep lapse rates would ensure with
potential for low topped convection. Since this is several days off
and no real agreement in models will keep temperatures conservative for
highs and hold off on any thunder mention. Low will take its own
Sweet time leaving the area still giving lingering effects outside
the current period.


Aviation...(for the 06z tafs through 06z Saturday morning) issued at
230 am EDT Friday Apr 25 2014

A mesoscale vorticity associated with an upper level system will race east early
this morning across central Indiana into Ohio. Given the track of
this system and deeper convection farther south along the Ohio
River...really pessimistic about numerous showers and low clouds over
northern Indiana...especially given overnight dew points just recovering
out of the 20s and upper air observation and aircraft sounding still showing a
very dry boundary layer. Have removed MVFR conditions at sbn and
FWA. Although a very brief MVFR ceiling is possible...ongoing observation are
nearly 100 percent VFR with high based ceilings. Kept a wind shift
early this morning...followed by some mixing the next several
hours will allow gusts between 25 and 30 kts. Winds should
decouple by early evening.


Iwx watches/warnings/advisories...


short term...Murphy
long term...Fisher

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