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Area forecast discussion 
National Weather Service Grand Rapids Michigan
329 PM EDT Tuesday Jul 7 2015

Latest update...
synopsis/short term/long term/marine

issued at 329 PM EDT Tuesday Jul 7 2015

A cold front is progressing off to the east of lower Michigan this
evening allowing cooler and drier air to filter in on northerly
winds. In fact...lows will dip into the 40s across central lower
Michigan tonight. High pressure sliding our direction from the
northern plains will bring fair weather from tonight through
Wednesday. The next weather maker for southwest lower Michigan will
brush the southern Great Lakes Wednesday night into Thursday with
rain expected along and south of Interstate 96. Highs both Wednesday
and Thursday will be below normal for this time of year holding in
the 70s.


Short term...(this evening through Thursday night)
issued at 329 PM EDT Tuesday Jul 7 2015

Main focus of the short term is on the precipitation event Wednesday
night into Thursday as a low moves across northern Indiana and Ohio.
Otherwise fair weather is expected in the short term.

All of the short term operational models...ECMWF...NAM...GFS and
Canadian Gem all take the surface low Wednesday night into Thursday
across portions of northern Indiana and Ohio. So...solid consensus
in a precipitation event for our south. The surface low is weak in depth
but appears compact and somewhat potent. The low is associated with
a middle level shortwave that is currently seen moving east across the
Texas Panhandle. Water vapor shows some tropical connection with the
shortwave and precipitable waters are around 2 inches as it passes across far
Southern Lower Michigan which is above normal even for early July.

Models seem to be struggling with the amount of precipitation across the
far south...but there is some hints that it could be on the heavier
side. Later forecasts will begin to nail this down as the wave
approaches. At this point have likely probability of precipitation across the south with a
pretty tight gradient as you head north across the County Warning Area. The far
northern County Warning Area will probably not see much in the way of rainfall.

Otherwise...expect decreasing clouds tonight as the diurnal cumulus
gradually fades and advects southward. Wednesday will be a partly
cloudy day as we see cumulus develop once again across the lower
peninsula. Thursday night looks dry with quiet weather as well as
the compact low will be headed east.

Long term...(friday through tuesday) issued at 329 PM EDT Tuesday Jul 7

Middle level flow will transition this weekend as the high over the
southeastern states migrates to the southern rockies. Models are in
fairly good agreement bringing warm front through the region
Saturday...which will result in a good chance of showers and storms.
Once the middle level ridge becomes established out west...pieces of
energy will move throughout the Great Lakes region in northwest
flow...which will continue the chances of precipitation into early
next week with temperatures in the 80s.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 137 PM EDT Tuesday Jul 7 2015

Initial concern for 18z tafs is with clearing low clouds. Satellite
loops and metars show a continued progression of clearing of low
clouds from northwest to southeast...and expect these to exit kjxn
by middle afternoon. area of Post frontal cumulus has
developed over northwest lower Michigan near kcad and krqb...and
models indicate this area should advect/develop into central
Michigan this afternoon. Do not expect these clouds to affect
kmkg...but other taf sites should see at least scattered clouds with
this feature. Will keep ceilings in place at kjxn until around
midnight as a result.

Other concern for this taf issuance is the potential for fog
development overnight into early Wednesday morning. BUFKIT
soundings suggest that low level moisture will be present...but
surface temperatures will not get cool enough to create dense fog.
With precipitation over for all taf sites and north winds/at least
partial clearing expected through sunset...some of the surface
moisture will be mixed out as well.


issued at 329 PM EDT Tuesday Jul 7 2015

Marine concerns are all in the first period of the
forecast...tonight. Strong north flow continues out on Lake
Michigan...with the South Haven light having touched gales in the
last hour. Waves at the South Haven buoy have now reached 8.8 feet
as of 300pm. The Small Craft Advisory and beach hazard statement
look solid. Running the northern half of the marine area headlines
through 1100 PM and the southern half through 500 am tonight.

Winds tonight will turn to the northeast...offshore...which will
bring waves down considerably. Winds will subside quite a bit late
tonight into Tuesday as we head toward 500 am marine
concerns in our nearshore waters and on our beaches should drop.

Winds and waves look to be benign Tuesday through Thursday night
with a weak pressure gradient in place across Lake Michigan.


issued at 1137 am EDT Tuesday Jul 7 2015

Locally heavy rain fell in the past 12 hours or so around and
north of Muskegon. Further southeast across southwest lower
Michigan...higher rainfall totals were a bit more scattered. This
has resulted in minor upward trends on area rivers and streams.
There are no immediate concerns for river flooding. However...this
may become a concern heading into next weekend.

Dry conditions are expected for the next 24 to 36 hours before
another round of precipitation reaches the southern third of the
forecast areas...mainly along and south of I-94. Some of the rain
may make up to I-96 but is expected to be lighter on the totals
along the northern fringes of the precipitation field.

The Friday through Sunday timeframe is still the main focus with a
boundary that drifts northward late in the week. Pending boundary
placement...rounds of showers and thunderstorms could add up to
general totals of 1-2 inches. Locally higher amounts are certainly
possible with the greatest threat for heavy rainfall existing
across the southern half of the County Warning Area...along I-96 and south. Given
recent rainfall and pending Wednesday night into thursdays
round...weekend rainfall could act more as runoff and lead to
quicker responses on rivers. River flooding may be something we
need to monitor through the weekend.


GRR watches/warnings/advisories...
Michigan...Beach hazards statement through late tonight for miz056-064-071.

Beach hazards statement until 11 PM EDT this evening for miz037-

Lm...Small Craft Advisory until 11 PM EDT this evening for lmz847>849.

Small Craft Advisory until 5 am EDT Wednesday for lmz844>846.



short term...Duke
long term...mws

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