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fxus63 kgrr 191151 

Area forecast discussion
National Weather Service Grand Rapids Michigan
751 am EDT Sat Oct 19 2019

Latest update...

issued at 331 am EDT Sat Oct 19 2019

- no major changes to the 7-day forecast were made with the
morning forecast package.

- Quiet weather is expected this weekend with above average
temperatures and low chances for precipitation.

- A storm system Monday/Tuesday will bring a chance of showers
areawide and gusty winds along the Lakeshore. Beach/Bluff
erosion remains a concern.

- Forecast confidence decreases from Wednesday Onward.


Discussion...(today through next friday)
issued at 331 am EDT Sat Oct 19 2019

National water vapor imagery overlaid with rap-analyzed 500 mb
heights depict a near sinusoidal upper-level wave across the
east half of the United States with a Horseshoe Ridge from the
Great Lakes to northeastern US and trough across the Southern
Plains. Regional surface observations show a frontal boundary
stretching from the Texas Panhandle through the Central Plains
into Manitoba along which scattered weak convection continues to
fester. Locally, temperatures are in the upper 30s away from the
Lakeshore with light southeast winds under clear skies.
Relatively quiet weather is expected through the weekend with the
biggest forecast concern remaining on the storm system expected to
impact the northern US during the Monday/Tuesday timeframe.

Today will start out mostly clear but clouds will increase this
afternoon as the aforementioned frontal boundary translates eastward
toward the Great Lakes. Highs are poised to rise into the lower 60s
areawide with a southerly wind (at times gusting 15-20 mph). As the
frontal boundary slips through overnight, we can't rule out a few
sprinkles mainly north of I-96 and west of US-131 but a lack of more
pronounced forcing (the parent low will be near Hudson bay) as well
as a somewhat unfavorable look to the jet stream (e.G.
Frontolysis) suggests precipitation potential is low. Sunday
continues to look glorious with light winds, clearing skies, and
highs in the mid to upper 60s with 70 not out of question.

As a secondary trough digs into the western US Sunday afternoon, a
low pressure system will develop in the Lee of the Rocky Mountains
and progress northeastward toward the western Great Lakes Monday.
While reasonable spread remains in both the deterministic and
ensemble model envelopes, a growing number of solutions feature
the brunt of warm-sector convection remaining to our south along a
prefrontal trough Monday afternoon as opposed to along the cold
front itself after dark Monday night, all the while as the surface
low tracking well to our northwest toward Western Lake Superior.
Our main concern remains on the potential for a prolonged period
of gusty winds especially along the Lakeshore Tuesday morning
through Wednesday. The trend in duration and wind speed from the
European model (ecmwf) eps continues to inch upward with the probability for
initially southwest becoming west gale force (34 kt/40 mph) wind
gusts now between 80-100% with mean sustained winds (which
largely drive wave heights) more than 25 kts along the Lakeshore
from 8 am Tuesday to 2 am Wednesday. As such, we remain concerned
for another round of Beach/Bluff erosion from initially Grand
Haven northward and then the entire Lakeshore.

Broad troughiness aloft will stall across the Great Lakes Wednesday
and beyond which leverages low predictability at this juncture
(spread in ensemble heights and 850 mb temperatures increases
significantly from Wednesday onward). There remains a signal for
some sort of low pressure system to develop out of the troughiness
toward the end of the week but whether it impacts the Great Lakes or
East Coast is hardly set in stone at this point.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 742 am EDT Sat Oct 19 2019

Skies are mainly clear across southwest lower Michigan at 12z.
Just upstream however mid and high clouds were beginning to invade
the area from the west. We should see an increase in clouds with
bases about 15,000ft today. A southerly wind will become a bit
gusty this afternoon at 10-20 knots.

Tonight, the wind will diminish to less than 10 knots. Clouds will
lower and thicken to bases around 5,000ft. Some scattered showers
are possible after midnight, especially at kmkg and kgrr. Not
expecting a restriction to visibility as the showers will be light
and sparse in coverage.


issued at 331 am EDT Sat Oct 19 2019

Southerly winds of 15 to 25 kts and waves of 3 to 5 feet will make
conditions decidedly choppy near the points through this evening.
Relatively calm conditions are expected Sunday before southerly
winds increase Monday afternoon. Winds will increase markedly
Tuesday morning out of the southwest and west by Tuesday evening
with gale force gusts to 35 knots looking increasingly likely.
With sustained winds of at least 20 to 25 kts, waves will increase
to 6 to 8 feet or larger Tuesday morning through early Wednesday
which will likely lead to Beach/Bluff erosion initially from
Grand Haven northward but eventually along the entire Lakeshore.
Conditions are expected to modestly improve after daybreak


GRR watches/warnings/advisories...
Lm...Small Craft Advisory until 8 PM EDT this evening for lmz847>849.



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