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Area forecast discussion 
National Weather Service Grand Rapids Michigan
323 am EDT Friday Jul 31 2015

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

issued at 314 am EDT Friday Jul 31 2015

Today and Saturday are expected to be dry. Breezy conditions once
again will occur today much like yesterday. Sunday will feature
increasing cloudiness with some showers and thunderstorms possible
especially across west central lower Michigan during the morning and
afternoon...with more widespread rainfall possible Sunday night.


Short term...(today through sunday)
issued at 314 am EDT Friday Jul 31 2015

Main focus is on the chance for thunderstorms on Sunday. An upper
low over Hudson Bay will meander south and amplify a longwave trough
across the eastern half of the Continental U.S.. split h250 jets over the
Midwest will create a zone of divergence over the Great Lakes. A 30-
35 knots low level jet noses in during the day while warm air advection and a
h850 thermal gradient develops over the lower peninsula.

With modest middle level winds...deep layer shear will not be
spectacular but will at least Register in the 30-35 kts range mainly
for the central and northern County Warning Area...with lesser readings across the
south. Surface based cape off the European model (ecmwf) does increase to 1000-2000 j/kg
during the day. Precipitable water values are expected to nose upward but do not
look extremely high. Showers and thunderstorms will likely get going
across WI/Illinois during the first half of the day and spread east during
the afternoon. The GFS and Gem are a bit quicker than the European model (ecmwf) with
developing precipitation over the area...which may stabilize the atmosphere
and reduce the risk for thunderstorms during the afternoon.

Outside of Sunday...dry weather dominates today and Saturday. Winds
will once again be noticeable today...with similar sustained speeds
and gusts probable. The ground is quite dry at this point for the
central and northern County Warning Area. Breezy conditions today may create
somewhat of a higher risk for spreadable fires...although dew point
readings will not be critically low. Still...something to be mindful
of if there are any Burns planned.


Long term...(sunday night through thursday)
issued at 314 am EDT Friday Jul 31 2015

A low pressure system and cold front will bring rain and
thunderstorms Sunday night into early Monday. It is noted that
overall short to medium range guidance trends suggest a somewhat
faster frontal passage such that the best chance for storms may come
Sunday night with dry weather for most of Monday.

Raised probability of precipitation some for Sunday night based on short to medium range
guidance trends the past 24 hours. Potentially moderate instability
will develop out ahead of this system Sunday. A few strong to severe
storms are possible Sunday night with decent instability potentially
in place and forcing from the low pressure and cold front and
increasingly favorable upper dynamics and increasing deep layer

A cooler and drier airmass will advect in behind that system for the
early to middle portion of next week as the upper level trough
becomes more entrenched into the Great Lakes region. In fact high
temperatures Tuesday through Thursday will likely only reach the 70s with
mins mainly in the 50s.


Aviation...(for the 06z tafs through 06z Friday night)
issued at 1207 am EDT Friday Jul 31 2015

VFR conditions will continue at all the terminals through the next
24 hours. West winds will increase to 15 kts with frequent gusts
to 20 to 25 kts from late Friday morning through Friday afternoon.
Winds will diminish Friday evening.


issued at 314 am EDT Friday Jul 31 2015

Close call on a Small Craft Advisory today...but opted not to
issue one with waves predominantly in the 2-4 feet range. While
winds will be 15-20 knots...the window for potential 3-5 feet waves
would be narrow (15z-20z) if any do occur. It is still possible
that one may be issued today based on trends. Overall it appears
similar to yesterday's setup...when 4 footers were observed. This
will need to be watched.


issued at 1232 PM EDT Thursday Jul 30 2015

River levels continue to fall and are expected to continue to fall
for at least the next week as rainfall amounts are not expected to
be enough to cause the rivers to start rising.


GRR watches/warnings/advisories...


short term...Hoving
long term...Laurens

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