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Area forecast discussion 
National Weather Service Grand Rapids Michigan
728 am EDT Tuesday Jul 7 2015

Latest update...
aviation

Synopsis...
issued at 315 am EDT Tuesday Jul 7 2015

A cold front will sweep across southwest Michigan during the middle
morning hours of today. Showers and a few thunderstorms are
expected this morning as the front moves through the area. Skies
will clear during the middle to late afternoon as cooler and drier
air moves in behind the front. High pressure will bring mostly
sunny skies Wednesday with highs only in the 70s. A wave on the
front may bring rain back to the areas near and south of I-94
Thursday.

&&

Short term...(today through thursday)
issued at 315 am EDT Tuesday Jul 7 2015

The primary issue today is the cold frontal precipitation event
already underway as I write this. The second issue the the wave on
the front that passes south of the area on Thursday.

The rain band with the front should clear the area by middle to late
afternoon. The threat for severe storms seems rather low since the
front is coming through middle morning and there is extensive clouds
and showers around. That will limit the instability needed for
stronger thunderstorms. The extensive area of rain with the front
is being helped by the deep lift created by the entrance region
the 95 knot polar jet...crossing Lake Superior this morning. Once
that is out of the way...skies should clear from west to east.

High pressure will keep Wednesday mostly sunny with afternoon
temperatures mostly in the 70s. The next wave on the front now
looks like it will mostly track just south of state Thursday. That
system is a southern stream wave that lifts northeast into
confluent flow from the polar jet over Michigan Thursday. That
should help keep that system just south of this area. Still it is
not out of the question areas near and south of I-94 could see a
little rain Thursday. If nothing else temperatures will be on the
cool side of normal now for several days.

Long term...(thursday night through monday)
issued at 315 am EDT Tuesday Jul 7 2015

The main focus of the long term will be the movement of a warm front
north through the County Warning Area over the weekend. Confidence is increasing
that part of the weekend will be wet. Both the European model (ecmwf)/GFS show surface
high pressure moving east and a warm front over the Northern Ohio
valley lifting north through the County Warning Area Saturday/Saturday night. There
should be a decent amount of moisture with this system as Gulf
moisture will get wrapped around the west side of the upper
retrograding Bermuda high. Precipitable water values around 2
inches suggests that heavy rainfall will be possible Saturday
night. Shear values around 35kts coupled with Li/S around -4c may
result in a few strong storms too. Upper waves moving around the
top of the Bermuda high will necessitate keeping probability of precipitation in the grids
through Monday.

Highs will mostly be in the 80s during the period.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 728 am EDT Tuesday Jul 7 2015

An area of IFR ceilings follows the cold front with a period of
showers. The extensive cloud cover will prevent any significant
thunderstorms from developing but even so...due to 2 inches of
precipitable water in the air...some of the showers will be very
heavy...if only briefly so. With the cold air coming in...expect
gusty north winds most of the day time hours at all of our taf
sites...once the front gets through. That may not be till 15z at
jxn. Clearing will follow quickly this afternoon...by 21z most of
our taf sites should be VFR. High pressure builds in tonight so
winds will become light from the north.

&&

Marine...
issued at 315 am EDT Tuesday Jul 7 2015

Not much change in the marine headlines. North winds of 15 to 25
knots should build waves to 3 to 5 feet by middle morning so it makes
sense to keep the headlines just as they are. I expunged the fog
from the near shore forecast as it does not look this this would
be much of an issue given how cool and dry the following the front
really is.



&&

Hydrology...
issued at 1119 am EDT Monday Jul 6 2015

No short term issues are foreseen on area rivers. Long term
forecasts spell some concern with heavier rainfall that may come
into the picture later this week.

Rivers all continue to be stable or falling slightly. Current
levels are a bit higher than normal by July standards due to the
heavier rainfall experienced in June. Rainfall tonight into
Tuesday will generally be one-half inch or less. While localized
areas could exceed this amount...widespread heavy rainfall is not
anticipated.

The second half of the week brings the possibility for multiple
waves of rainfall along a boundary that could set up somewhere
through the Great Lakes region. Confidence is low with expected
rainfall totals...but current consensus with wpc guidance suggests
one to two inches is possible right through next weekend...from
Friday through Monday. Forecast variability with the boundary will
require a bit more attention to updates through the next several
days.

&&

GRR watches/warnings/advisories...
Michigan...Beach hazards statement through this evening for miz037-043-050-
056-064-071.

Lm...Small Craft Advisory until 11 PM EDT this evening for lmz844>849.

&&

$$

Synopsis...wdm
short term...wdm
long term...04
aviation...wdm
hydrology...jam
marine...wdm

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