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Lawrenceville Weather

Area Forecast Discussion

FXUS63 KIWX 302354

Area Forecast Discussion
National Weather Service Northern Indiana
754 PM EDT THU JUN 30 2016

Issued at 745 PM EDT Thu Jun 30 2016

A ridge of high pressure that has been responsible for fair
weather across the region will continue to depart to the east this 
evening. This will allow the next upper level disturbance and
cold front to approach from the northwest bringing a chance of
rain showers and a few embedded thunderstorms late evening into
the overnight hours. Gusty northwest winds behind the front will
lead to hazardous swimming conditions on Lake Michigan late
tonight through Saturday morning. Lows tonight will be in the 60s.
Highs Friday will be in the 70s, although highs near the Lake
Michigan shoreline are expected to remain in the upper 60s.


Issued at 745 PM EDT Thu Jun 30 2016

A weak lead short wave is progressing through northwest Indiana at
the current time, although this lead wave is likely to do little
more than aid in top-down saturation. Primary upper level trough
still lingers back to the northwest, and large scale forcing from
this wave is expected to increase toward 06Z. The strongest
forcing is expected to remain across far northern portions of the
forecast area and northward across lower Michigan however. Could
see a few showers develop over the next few hours across the far
west as lead low level theta-e gradient continues eastward.

A solid line of showers and thunderstorms has developed over the
past several hours across southern/eastern Wisconsin. A narrow
axis of deeper moisture will immediately precede the associated
cold front. While pooled moisture axis will not be overly
impressive in terms of magnitude, expecting enough moisture
pooling when accompanied with uptick in upper level forcing and
associated low level convergence axis to allow band of precip to
overspread southern Great Lakes in the 04Z-08Z timeframe. Made a
slight upward adjustment to PoPs earlier this evening based on
upstream convective trends, although trends from past hour
indicate weakening of convection across east central Iowa with
refocused convective development across southeast Iowa.

Confidence in PoPs somewhat lower for southern half of the area
given recent trends and strongest forcing across the north, but
elevated instability should be greatest across southwest portions
of the area which should aid in additional shower development as
upper trough approaches, and possible upwind development from
primary area of precip tracking across the southern Great Lakes.
Kept thunder mention as a chance, due to instability magnitude
lower with eastward extent across local area and an unfavorable
diurnal timing of cold front. A few showers may develop behind
frontal precip overnight as upper trough swings through, although
probably not to the extent as currently being observed across
northwest Wisconsin where mid level lapse rates are maximized.


.SHORT TERM...(This Evening through Saturday night) 
Issued at 202 PM EDT Thu Jun 30 2016

Water vapor imagery and latest RAP analysis depicting short wave
rotating into the northern great lakes region this afternoon.
Regional radar showing line of showers and thunderstorms along
associated cold front. Moisture pooling along and ahead of cold
front has dewpoints climbing into the 60s over southern MN and
IA...resulting in destabilization of airmass with daytime heating as
CAPES now over 2000J/Kg. Latest hires guidance has precip reaching
NW CWA around midnight and exiting the area early Friday morning.
Loss of daytime heating and lack of deep layer moisture will
significantly diminish instability once system arrives tonight.
Better forcing will be displaced north of our area but mass
convergence along front should still support scattered convection
overnight...will continue to monitor radar trends but for now plan
to keep pops in chance range. Cool dry Canadian high pressure will
build into the region behind frontal passage and bring clearing
skies by Friday afternoon and a very pleasant start to the holiday
weekend with sunny skies and low humidity Saturday...highs in the
70s and lows in the 50s. 


.LONG TERM...(Sunday through Thursday) 
Issued at 202 PM EDT Thu Jun 30 2016

Frontal boundary will stall along the TN valley this weekend...short
wave energy ejecting out of the four corners will develop frontal
wave that will track into the mid-MS valley on Sunday. Models
vary on timing and evolution of convective complex that is
expected to develop with this feature with the GEM further north
and latest GFS has now flipped to further south than the ECMWF.
Low confidence pattern but solutions close enough to our area to
warrant maintaining low chance pops. Once this wave exits off to
the east models diverge as 12Z GFS has upper ridge expanding into
our area while 00Z ECMWF has northern stream flow continuing to
impact our region with weak transient systems. This leaves us with
a blended forecast of sloppy low chance pops through much of the
remainder of the extended forecast. Did adjust blend to limit pops
to chance range in southern CWA Sunday night and
values Tuesday night to keep forecast dry in wake of exited


.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 745 PM EDT Thu Jun 30 2016

Not much change from previous TAFs with main concerns continuing
to center on convective potential late evening/overnight. Upper
trough/cold front will continue to approach northern Indiana late
evening into the overnight hours. More vigorous convection is
expected to remain well northwest/west of the area this evening
with mainly an area of rain showers with a few embedded
thunderstorms working across northern Indiana from west to east in
the 04Z- 09Z timeframe. Precip confidence remains slightly greater
at KSBN in closer proximity to stronger upper forcing, but
expecting bulk of shower threat to shift east of terminals after
09Z. Some concern that cigs below fuel alternate criteria could
develop behind the front late tonight into Friday morning due to
residual low level moisture/shallow frontal inversion, but will
continue to keep cigs at 2000 ft for this period due to low
confidence, and let future amendments/issuances address this


.IWX Watches/Warnings/Advisories...
IN...Beach Hazards Statement from 4 AM CDT Friday through Saturday 
     morning for INZ003.

MI...Beach Hazards Statement from 5 AM EDT Friday through Saturday 
     morning for MIZ077.

LM...Small Craft Advisory from 5 AM Friday to 8 AM EDT Saturday for 




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