Area Forecast Discussion
Issued by NWS Northern Indiana

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183
FXUS63 KIWX 242335
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
735 PM EDT Sun Jun 24 2018

.SYNOPSIS...
Issued at 335 PM EDT Sun Jun 24 2018

An isolated shower is possible this evening across south central
Lower Michigan and far northwest Ohio, but otherwise dry
conditions are expected from tonight through later Monday night.
The next system to affect the area will be Tuesday and Wednesday
when some locally heavy rain is possible along with a potential of
a few strong storms. Dry weather will return for Wednesday night,
but heat and humidity will build for Thursday and Friday. Low
temperatures tonight will range from the mid 50s to lower 60s.
High temperatures on Monday will range from the mid 70s across
south central Lower Michigan to the lower 80s across west central
Indiana.

&&

.SHORT TERM...(This Evening through Monday)
Issued at 335 PM EDT Sun Jun 24 2018

Large scale cyclonic flow continues across the Great Lakes region
this afternoon. Water vapor imagery indicates a well defined vort
max headed across western Lake Erie vicinity which appears to be
associated with more concentrated area of rain showers across
southern Lake Huron. While not as evident on satellite imagery,
model initializations do suggest presence of another upstream
vort across southern and central Lake Michigan which will slowly
drop southeast across the region tonight. Combination and
progression of these two perturbations will drive another low
level trough axis southward late this afternoon into this evening.
Visible satellite imagery starting to indicate a more well
developed cu field forming from Kalamazoo to Toledo. Modification
of earlier AMDAR sounding across the northeast suggests minimal
instability on the order of 200-400 J/kg. Instability likely a bit
more substantial for locations along Route 30 corridor, although
forcing will be lacking until upstream Lake Michigan vort max
slowly sags southeast into this evening. Previous forecast of
slight chance/low chance PoPs across the east/northeast through
early evening still appear to be on track and not expecting to
make major changes.

Low rain chances will diminish after 00Z with loss of diurnal
instability given weak nature to mid/upper level forcing.
Otherwise, just some increased clouds across the east to persist
into this evening with vort passage before mainly mostly clear
skies for remainder of the night. A punch of dry low level air to
build across the region later tonight in wake of low level trough
this evening, which will allow mins tonight into the mid 50s to
lower 60s.

Upper riding and associated sfc anticylcone to build across the
region on Monday with any shower activity remaining well south of
the forecast area. Near seasonable temps are expected with continued
low humidity levels.

&&

.LONG TERM...(Monday Night through Sunday)
Issued at 335 PM EDT Sun Jun 24 2018

Late Monday night will mark the beginning of another active weather
period that will continue through Wednesday. A slow moving upper
level low will approach the region from the Central Plains. Guidance
is in general consensus of lead short wave kicking out of larger
negative height anomaly early Tuesday. Some question as to how
upstream nocturnal convection would be maintained into local area
for first part of Tuesday given initially meager instability
profiles, although advective forcing will be on the increase early
Tuesday. Mid levels somewhat on the warm side raising some questions
as to extent of destabilization on Tuesday, and a good deal of
uncertainty exists with how overnight storms will modify environment
for Tuesday. Latest 12Z suite of guidance would suggest greatest
severe potential probably remaining just west of local area in pre-
frontal trough type environment closer to better mid/upper level
support across Mid MS Valley. May have to watch for some strong/severe
threat into at least western portions of the area later Tuesday
afternoon/evening as shear profiles will be on the increase with a
50 knot 500 mb speed max approaching. Again, the main
uncertainties for severe potential are possible unfavorable
diurnal timing to strongest forcing and instability magnitude
uncertainty.

Potential for heaviest rain would appear to be Tuesday night into
possibly early Wednesday as pre-frontal trough moves in with
respectable 1.75-2 inch PWATS in place. There should be at least
some decent progression with primary upper level low however, which
may alleviate higher end heavy rain concerns. With recent heavy
rainfall across portions of the area, did consider an ESF this
afternoon to highlight Tue/Wed flood potential, but will defer to
later shifts with still a good deal of uncertainty how
timing/instability will play out.

Conditions dry out for Wednesday night and Thursday with the main
weather story beyond this point on building heat. Medium range
models have been fairly consistent in ridge amplification with
larger uncertainty to what extent to dampen the ridge later next
weekend with next larger scale wave working across the northern tier
of CONUS. Heat indices in excess of 100 are at least a possibility
for portions of the Fri-Sun period. With uncertainties in timing
this next upper wave next weekend, and several different solutions
on extent of ridge suppression, will keep the post-Wed night
period dry.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 729 PM EDT Sun Jun 24 2018

VFR tafs issued this period but a couple features to watch this
evening and overnight that could bring some MVFR cigs to
terminals. The first feature can be seen across lower Michigan in
satellite imagery. A weak boundary was slowly sagging south toward
KSBN but expectation is that clouds associated with this feature
will disspate with loss of sun as it nears KSBN. Cigs hovering
near 3kft so will watch next few hours. Second feature of note
will be a potential area of lower clouds coming off of Lake Erie
and moving west overnight as low level flow becomes east to
northeast. Hires guidance bringing low end MVFR cigs into KFWA
overnight but this guidance has a low and overdone bias. Will be
keeping an eye on this but did keep the bkn035 but moved up timing
a bit to match guidance suggestion of timing if it indeed
materializes. Otherwise VFR on Monday with east to northeast sfc
winds around 10 knots.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Lashley


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