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Area forecast discussion 
National Weather Service northern Indiana
541 PM EDT Friday may 29 2015

issued at 528 PM EDT Friday may 29 2015

There is a chance for some rain tonight ahead of an approaching cold
front. Low temperatures tonight will be in the upper 60s. Shower
and thunderstorm chances increase tomorrow as the cold front moves
through the region. High temperatures tomorrow will range from
the lower 60s near Lake Michigan to the lower 80s in southeastern


Short term...(this evening through saturday)
issued at 341 PM EDT Friday may 29 2015

Nearly 1000 j/kg of MLCAPE in an uncapped warm sector will continue
to support isolated showers (maybe a rumble of thunder) through
the middle-late afternoon hours as remnant outflow attached to
shortwave lifting NE into the western lakes settles in. Loss of
diurnal heating and little middle/upper level support should result in
a mild/mainly dry period tonight. With that said ramp up of low
level jet (lingering elevated instability) in advance of this
upstream feature...and potential for convectively induced/aided
vorts to lift through in moist SW flow suggest maintaining at least
low chance probability of precipitation for showers (highest west) the way to go.

On Saturday...large scale ascent increases with time as vigorous
northern stream pv anomaly dropping southeast through Ontario partially
phases with a shearing shortwave that will be working toward the
middle MS valley. There will also be separate convectively aided vorticity
that will be in the act of lifting into the western Ohio Valley by
later in the day. In the low levels...a baroclinic zone will
gradually shift southeast through western/northern zones morning/early
afternoon and points southeast during the afternoon. The fgen/deformation
response under the rrq of a strengthening upper jet off to the
northeast appears impressive by Saturday afternoon/evening....with
when combined with more than ample moisture (850 mb mixing ratios
pushing 10-11c) should be enough to provide the entire area with a
decent rain event (especially later Saturday aftn-eve). There also
remains a very low chance for strong-severe multicells in the
afternoon across southern/eastern zones if enough heating occurs
with stronger flow/shear expected to lag just behind the surface


Long term...(saturday night through friday)
issued at 341 PM EDT Friday may 29 2015

Rain showers...with perhaps some embedded thunder expected to
continue into Saturday evening as upstream trough currently across
Nebraska Panhandle region approaches the region. A rather impressive
water vapor presentation of this wave noted this afternoon across
the Central Plains...and last few runs of bulk of guidance have
trended toward a slightly slower and more amplified solution
concerning this wave. Small differences in the nature of this wave
will have a big impact on low level baroclinic zone placement and
longevity of rain across the area into Sunday morning. Given current
observational trends and majority of dprog/dt data...have generally
bought in on a more amplified solution and have increased probability of precipitation for
the Saturday evening period as low/middle level fgen forcing persists
across the area in advance of this wave. Anafront characteristics of
this baroclinic zone will also support good deal of elevated
moisture behind the surface cold front with NAM keeping upwards of
1.5 inch precipitable waters even across northern portions of County Warning Area late in the
evening. Some isolated thunder may persist into Saturday evening
especially for southeast half of the area...but storm total rainfall
amounts will likely be the primary concern through Saturday evening
with amounts in excess of an inch possible for southeast two thirds.

Confidence diminishes further in regards to probability of precipitation for late Saturday
night into early Sunday with 12z ec/NAM still depicting stronger
southern stream short wave lifting out of the Southern Plains that
may interact with the strong low/middle level thetae gradient. Have
maintained sharp northwest to southeast pop gradient for
Sunday...with highest chance probability of precipitation across the southeast. This period
will likely need further pop adjustment over the next few forecast
cycles once confidence increases regarding nature of this southern
stream wave and sheared vorticity maximum lifting into the Ohio Valley.

Otherwise...much cooler conditions in store for Sunday and have
continued trend of previous forecast in a slight slowing of
moderating temperature trend as more pronounced northern stream
trough helps reinforce Great Lakes thermal trough. Upper ridging to
build across the area toward midweek resulting in a sharper warming
trend...with temperatures up near 80 again by Wednesday. Precipitation chances
look minimal at least until Friday as middle/upper level ridging


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1241 PM EDT Friday may 29 2015

Scattered rain showers/isolated thunder on eastern fringe of remnant middle level
circulation lifting through northwest Illinois into southern WI should lift through
ksbn this afternoon. Brief visible restrictions possible with heavier
showers here. Lesser chances for precipitation/impacts at kfwa farther
removed from shortwave...although still could see an isolated
rain showers/storm here in an increasingly unstable airmass. VFR with
southerly winds generally 10-15 kts otherwise into the early
evening. Mainly VFR into tonight as well given expected lull in
precipitation coverage as boundary layer stabilizes...although hard to
completely rule out a few showers as weak disturbances will
continue to lift NE in moist SW flow. Better chances for
rain/storms and restrictions arrive tomorrow with primary frontal


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory from 2 PM Saturday to 5 PM EDT Sunday for



short term...steinwedel
long term...marsili

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