Area forecast discussion
National Weather Service northern Indiana
832 PM EDT Tuesday Jun 18 2013
Synopsis...
issued at 331 PM EDT Tuesday Jun 18 2013
A weakening frontal boundary will slowly drop into central Indiana
by this evening. A disturbance will drop southeast along the front
this afternoon...allowing for a chance of showers and
thunderstorms...mainly south of US 24. High pressure will build in
across the region with seasonable temperatures and dry conditions.
&&
Update...
issued at 812 PM EDT Tuesday Jun 18 2013
Updated to remove late afternoon wording from zone forecast product and to remove slight
chance probability of precipitation from southern portion of County Warning Area this evening. Drier air advecting
into southern portion of County Warning Area from the NE appears to have stabilized
airmass sufficiently to prevent deep convection from developing in
this area despite some forcing associated with vorticity maximum moving into
Indiana as well as weak low level convergence along inverted trough
and lake breeze. Minor adjustments also made to sky/temperature grids
otrws no significant changes made to the rest of the forecast.
&&
Short term...(this evening through wednesday)
issued at 331 PM EDT Tuesday Jun 18 2013
Morning stratus deck across northern areas has given way to strong
mixing...allowing temperatures to recover quickly and generally match with
temperatures in the south where sunshine has been abundant. Main difference
in terms of instability was higher surface dewpoints existed in southern
areas closer to stationary boundary draped from central Illinois to
southern Indiana. Widely scattered showers/storms have begun to
develop along this boundary with the main focus expected to remain
there as short wave energy continues to drift southeast into the
same area. This makes for a difficult forecast for probability of precipitation into this
evening across southern areas with boundaries to aid in development
few and far between. Best potential lies with what appear to be lake
breeze setup from near Kankakee Illinois into valpo and towards Benton
Harbor. A few returns have been noted across north Illinois along this
boundary which was drifting southeast. However this may only impact far SW
locations with remainder of the area left high and dry. While I
can't rule out a pop up shower or storms anywhere across the
area...have trimmed probability of precipitation and confined to SW areas with greater
potential. By middle evening any threat will be gone with dry
conditions settling in for the remainder of the period. Dewpoints in
the 40s and even a few 30s will move SW into the area overnight into
Wednesday.
&&
Long term...(wednesday night through tuesday)
issued at 331 PM EDT Tuesday Jun 18 2013
A warming trend and mainly dry weather remain the primary highlights late
this week into the upcoming weekend as a Southern Plains/intermountain
west upper ridge builds northeastward into the Midwest and Great
Lakes. Weak middle level disturbances spilling out over the ridge from
a Pacific northwest/northern rockies negative height anomaly will
interact with a developing instability gradient/frontal zone to
produce a typical mesoscale convective system ring of fire type pattern across the northern
plains east into the upper Midwest...eventually into the Great Lakes
by this weekend. The local area will be in a somewhat precarious
position on the northeast fringe of this feature Friday into
Saturday morning as the Theta-E ridge mixes north...although expect
approaching activity to dry up initially late Thursday night into
Friday given lingering low level ridging/drying over the area. With
this and nose of low level jet focusing well northwest of the forecast area left the
forecast mainly dry through Friday night.
The upper level ridge axis will fold east over the area Saturday and
then just south and east Sunday into early next as the northern
rockies shortwave trough lifts east-northeast into the northern
plains and upper Midwest/Ontario. An active frontal boundary will
lay out under deep west-southwest flow later Sunday into early next
week. A model consensus favors better storm chances remaining north
of the iwx County Warning Area in vicinity of this synoptic front for these
periods...although hard to predict possible composite outflow
boundaries pushing farther south from mesoscale convective system activity into an unstable
environment. Lowered probability of precipitation in several periods as expect mainly
dry/hot weather under capped ridge...although could not pull probability of precipitation
completely (especially north) given above mentioned mesoscale
uncertainties and pattern recognition. Otherwise...only minor tweaks
to temperatures with preference to warmer highs over cool/climatology biased
consall guidance.
&&
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 702 PM EDT Tuesday Jun 18 2013
VFR conditions across the region this evening will continue through
the 00z taf period as dry airmass associated with upper Great Lakes high
advects into the area. Cumulus field over the area should give way to
sky clear this evening with loss of diurnal heating. Expect sufficient
moisture and low level instability for just a few cumulus redeveloping
during the day Wednesday.
&&
Iwx watches/warnings/advisories...
in...beach hazards statement until 4 am CDT Wednesday for inz003.
Michigan...Beach hazards statement until 5 am EDT Wednesday for miz077.
Ohio...none.
Lm...Small Craft Advisory until 5 am EDT Wednesday for lmz043-046.
&&
$$
Update...jt
synopsis...Fisher
short term...Fisher
long term...steinwedel
aviation...jt
Visit US at www.Weather.Gov/iwx (all lower case)
Follow US on facebook...twitter...and youtube at:
www.Facebook.Com/US.Nationalweatherservice.Northernin.Gov
www.Twitter.Com/nwsiwx
www.Youtube.Com/nwsnorthernindiana
