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Area forecast discussion 
National Weather Service northern Indiana
318 PM EDT sun may 3 2015

Synopsis...
issued at 312 PM EDT sun may 3 2015

An upper disturbance tracking along the Canadian border will drag
a cool front southward across the Great Lakes region. This front
combined with increasing moisture will likely produce showers and
thunderstorms from late tonight into Monday night. Lows tonight
will fall back only to the middle to upper 50s. Highs on Monday
will be in the 70s.

&&

Short term...(this evening through monday)
issued at 312 PM EDT sun may 3 2015



Focus of the short term period is precipitation/thunderstorm chances
associated with an incoming cold front.

An upper level low digging into northern Ontario this evening will
continue into Quebec through Monday. Our County Warning Area lies on the northern
most fringes of a ridge aloft...which is firmly anchored over the
southeastern United States. As always...we will be susceptable to
weak shortwave disturbances that meander through the nearly zonal
flow. Surface low pressure trough and associated cold front draped from
James Bay to the Dakotas will drift eastward overnight...finally
reaching our northwest County Warning Area by late Monday morning...then stalls in the
central County Warning Area in the afternoon.

For tonight then...moisture transport increases out ahead of the
front...especially as south-southwest winds bring in moisture from
the Gulf region. Ll remains fairly dry until late tonight
however...so expect precipitation to hold off for most areas until
morning hours.

Otherwise...pesky mesovortex spinning across eastern Iowa and northern
Illinois with showers/T-storms this afternoon is set to lift northeastward
through the early evening hours. Some models bring light precipitation into
the far western County Warning Area associated with this feature this evening...but
others take it to our north. Kept a slight chance of rain showers to
account for this...but not really confident. Dry air over our County Warning Area is
fairly entrenched for now.

Beyond that...Monday morning/Monday afternoon stronger forcing per
850-500mb qvector convergence arrives along with precipitable water values
ranging from 1 to 1.5 inches. Have precipitation chances gradually
increasing from the northwest after 06z tonight...then expanding
into the rest of the County Warning Area Monday. Kept highest probability of precipitation between
15-00z.

Thunder appears probable as well...with at least 500 j/kg MUCAPE in
the am...increasing to upwards of 1000 j/kg in the afternoon. As far
as the severe weather threat...not expecting anything substantial as
0-6km bulk shear is less than 30 knots for the day. Storm Prediction Center still keeps
US in the marginal category...which seems reasonable given
instability.

Temperature-wise we look to be on track...with highs a little bit
cooler for Monday compared to today in the northwest...mainly due to
cloud cover/precipitation and wind switch to the west.

&&

Long term...(monday night through sunday)
issued at 312 PM EDT sun may 3 2015

Strong northern stream SW continues to churn eastward through the nepac and by all
model accounts will dig southward into The Four Corners area by Friday before
ejecting northeastward sometime lt next weekend.

Until then primary weather ftr of interest this period is trailing frontal boundary
in association/West Lead northern stream disturbance swinging eastward through southern
Canada early before it washes out lt Tuesday. Highres guidance window has
nothing to build a consensus solution on what arises out of generally
weak background frontal scale ascent Monday night or Tuesday. More vigorous
but widely dissparate highres output tied to uncertain upstream
convective development especially Monday afternoon and overnight here. Thus will hold
west/prior pop Monday night-Tue.

After that...strong middle level ridge expected downstream of developing western troughing
and upstream of system developing off southeast coast. Warming trend seen in prior
MOS guidance looks to have run its course however middle teen 850 mb temperatures
Friday-Sat may yield middle 80s pending cloud cover/precipitation extent if any.
Current numbers align well west/latest MOS guidance and generally left
alone.

&&

Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 141 PM EDT sun may 3 2015

Tonight expect cloud cover to gradually increase at the taf
sites. A cold front will bring rain showers to the area Monday.
Precipitation will move into ksbn by Monday morning...then into
kfwa later in the afternoon. Thunderstorms are also
possible...especially later into the afternoon hours.
Overall...conditions will remain VFR for the most part.
Visibilities/ceilings could drop to MVFR during rain
showers/thunderstorms tomorrow...but confidence was not high
enough to include in the taf.



&&

Iwx watches/warnings/advisories...
in...none.
Michigan...none.
Ohio...none.
Lm...none.
&&

$$

Synopsis...mesoscale discussion
short term...mesoscale discussion
long term...T
aviation...mesoscale discussion



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