Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
646 am EDT Tuesday Jul 22 2014
issued at 434 am EDT Tuesday Jul 22 2014
Hot and humid conditions will overspread our area today ahead of
a cold front dropping southeast from the upper Midwest. The front
will move across our area tonight and Wednesday... possibly
accompanied by thunderstorms. Highs today will be in the lower 90s
with lows tonight in the upper 60s and lower 70s.
Short term...(today and tonight)
issued at 425 am EDT Tuesday Jul 22 2014
Shortwave over northern Minnesota early this morning is expected to move east-northeast into
southern Ontario today with associated cold front moving to western Michigan/northwest Illinois by
this evening. Plume of >20c 850 mb temperatures expected to advect into our County Warning Area
ahead of the front. This warm layer will likely inhibit deep
convective development along the front today as it moves across
Iowa/northern Illinois/southern WI and should result in little cumulus development in our
area allowing for mostly sunny skies. The nearly full insolation
combined with increased southwesterly gradient winds ahead of the front
should allow for fairly deep mixing in our area today resulting in
highs at or a bit above MOS temperatures... in the l90s.
Upper trough will deepen over the Great Lakes tonight as rockies ridge
amplifies. Decent low level convergence along the front combined
with gradual cooling aloft associated with the deepening upper level
trough may allow thunderstorms to develop in our area overnight. On the
other hand... the low level jet will shift well to our north overnight so a
mechanism to maintain instability will be lacking. Thus...
highest probability of precipitation maintained over northwestern portion of the County Warning Area where
lingering moderate instability will reside as front moves into
the area. Models also suggest 30-40kt 0-6km shear in this area
which would aid storm/updraft longevity/strength should deep
convection develop... so severe storm possible. Cold air advection following the front
should drop temperatures into the m60s northwest by daybreak while southeast likely
only falls to the l70s.
Long term...(wednesday through monday)
issued at 425 am EDT Tuesday Jul 22 2014
A cold front will be moving across the area Wednesday. Favor the
high res/convective allowing models which appear to reasonably
handle the cold start conditions. Therefore...given a substantial
low level inversion still present at the start of the period
Wednesday morning...believe it will be hard for storms to form. Middle
level lapse rates between 700/500 will be near 8c/km...but this area
which includes elevated cape will be hard to tap given very stable
conditions below this layer. Therefore...have lowered storm chances
Wednesday. Expect most activity should remain relatively isolated.
Cool conditions return again late this week with the coolest
temperatures expected Thursday night. Lowered temperatures considerably
including cutting temperatures 5 degrees over most areas...and around 10
degrees over northern Berrien County. Given the recent cold air
intrusion with lows in the 40s...and given the Canadian eps grams
with the mean ensemble lows Thursday night at Fort Wayne around 54
degrees...feel the GFS/mex values are in the park. Otherwise...the
next system will move into the area this weekend. Made few changes
to this period as the ongoing timing of this systems appears on
track in light of the latest GFS run.
Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 643 am EDT Tuesday Jul 22 2014
Warm/dry conditions aloft associated with upper level ridge over the
area should result in VFR conditions with little or no cumulus today.
Cold front over Iowa/Nebraska at this time will move across northern Indiana late tonight...
possibly accompanied by thunderstorms and rain with the best chance at sbn where more
instability is expected... while at FWA risk still seems too low
to mention in tafs. Modest SW winds expected today ahead of the
front... shifting to northwest late tonight as the front moves through.
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