Area forecast discussion
National Weather Service northern Indiana
129 PM EDT Wednesday may 22 2013
Synopsis...
issued at 1150 am EDT Wednesday may 22 2013
Low pressure over northwest Illinois will move east across Southern Lower
Michigan this afternoon and to southern Ontario tonight. A weak cool front
will trail to the south of the low and move east across southern
Michigan... Indiana... and most of Ohio by Thursday morning...
while a second stronger cold front drops south across the upper
Great Lakes. Scattered showers and thunderstorms are expected
along and ahead of the first cool front... while scattered showers
may accompany the second cold front.
&&
Update...
issued at 1150 am EDT Wednesday may 22 2013
Minor update to grids mainly to account for slower rise in temperatures
this morning due to extensive cloud cover and scattered showers
across area. Highs may struggle to make it out of the middle 70s and
have lowered highs a degree or two...especially across Northwest Ohio zones.
Afternoon forecast still a bit uncertain in terms of convective
development and severe potential. Convection attempting to fire
along cold front back in central Illinois with another area just to
the north that developed in area of partial clearing. Latest hires
models show storms moving into area after 18z and moving east into
Northwest Ohio by early evening. Slight risk of severe remains mainly
east of i69 with best chances to east of County Warning Area. Even though ll shear is
decent with forcing from upper level wave rotating around base of
trough...instability will be marginal and will depend on how much
clearing takes place over next several hours. Will ride with going
probability of precipitation/weather grids until forecast specifics and timing can be better
nailed down.
&&
Short term...(today and tonight)
issued at 440 am EDT Wednesday may 22 2013
Upper low over southern Minnesota expected to move east-southeast today/tonight and gradually
shear out/merge with northern stream trough dropping south from Hudson
Bay to the upper Great Lakes. Associated broad surface low should move east
from Iowa across Southern Lower Michigan today and into southern Ontario tonight with
an accompanying weak cool front moving east across our County Warning Area.
Combination of weak uvm associated with these features and some
diurnal destabilization expected to result in showers/thunderstorms in the
area... mainly this afternoon. Afternoon cape expected to be 1000-1500j/kg
with 30-35kt 0-6km shear and steep low level lapse rates. This may
allow some of the storms to become severe with damaging winds and
large hail possible this afternoon... particularly over Northwest Ohio where frontal passage
will be later allowing for better opportunity to destabilize.
A stronger cold front associated with the approaching northern stream trough should
drop into southern lm by dawn Thursday. Forcing tonight however should be
weaker as middle/upper level wind field over the area gradually weakens as
upper low shears out. Given this scenario... stayed close to
inherited chance pop grids for tonight.
Highs today generally forecast a few degrees above MOS based on
recent cool bias and mild start to the day. Cool front should
result in a little lower mins tonight... ranging from around 50
near Lake Michigan to around 60 far southeast.
&&
Long term...(thursday through tuesday)
issued at 440 am EDT Wednesday may 22 2013
A secondary upper level trough will move southeast across the western
Great Lakes region Thursday as cooler air spreads southeast. The
upper level support should be sufficient to produce showers...
although there should be a well defined northwest edge/ending of the
precipitation given the subsidence behind the trough. Put some detail
in the grids in this regard Thursday with the best chance for rain
early in the day. Added patchy frost northern areas Thursday night.
Skies should clear with winds becoming light most areas. Otherwise...
kept the rest of the forecast dry. Spectral models providing a range
of handling the short wave energy moving east as the upper level
ridge amplifies over the eastern half of the Continental U.S.. the European model (ecmwf) keep
the entire period dry and appears reasonable with this solution.
&&
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 117 PM EDT Wednesday may 22 2013
Scattered showers beginning to fire across area ahead of first of
two cold fronts as subtle destabilization is occurring in areas of
partial clearing. VFR conditions present at taf issuance but MVFR
conditions likely from time to time at both terminals during
periods of heavier showers and isolated thunderstorms and rain this afternoon into
evening. Still uncertain on timing and coverage so have covered
this with tempo group through 21-22z at both terminals. Showers
will linger overnight into the morning hours as secondary cold
front moves through area. Models hinting at period of IFR or even
LIFR conditions after 6z with frontal passage. Have trended visby and ceilings down
a bit but hesitant to deteriorate conditions that much until
trends can be better nailed down. Winds will be in the 8 to 15 knots
range for the period and will veer from SW this afternoon to northwest by
late Thursday morning.
&&
Iwx watches/warnings/advisories...
in...none.
Michigan...none.
Ohio...none.
Lm...gale watch from Thursday afternoon through Thursday evening for
lmz043-046.
&&
$$
Update...ceo
synopsis...ceo
short term...jt
long term...skipper
aviation...ceo
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