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000
FXUS63 KGRR 131716
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
116 PM EDT Sun Aug 13 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 AM EDT Sun Aug 13 2017

Quiet weather conditions are forecast today due to high pressure
situated over the Great Lakes region. An increase of high clouds
will be noted this afternoon with high temperatures up around 80
degrees. A few light showers are possible Monday afternoon although
most areas look to stay dry. Highs will be near 80 once again on
Monday. Another mainly dry day is forecast on Tuesday with a
developing warm front off to our southwest. Highs on Tuesday will
push into the lower 80s. Overall fairly seasonable weather for this
time of year.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 330 AM EDT Sun Aug 13 2017

High pressure will bring fair weather today and tonight, with an
increase in high cloud with time through Monday morning. Expecting a
mostly sunny day today, but there will be increasing high clouds in
the afternoon. A well defined upper shortwave trough can be seen in
the water vapor imagery this morning stretching from the Northern
Plains south into Nebraska. Showers are associated with the
shortwave at this time well off to our west. We will stay dry
through Monday morning with high pressure in place across the Great
Lakes.

The surface high slips away to the east on Monday allowing a weak
surface trough associated with the upper wave to approach. Have
blended in with neighboring offices showing small chances for light
rain showers Monday afternoon, but would not be surprised to see us
stay dry. Have 20 pops in the forecast Monday afternoon.

Monday night into Tuesday the surface trough washes out with a
developing warm front to our southwest. Similar reasoning in both of
these forecast periods as well, small pops in the forecast to
maintain consistency with neighboring offices. Thinking the bulk of
this time frame will be dry as well. An increase in cloud cover will
be associated with the shortwave aloft through especially Monday and
Monday night. Highs will be around 80 today, Monday and Tuesday.

.LONG TERM...(Tuesday night through Saturday)
Issued at 330 AM EDT Sun Aug 13 2017

The high pressure ridge will continue in control of the wx pattern
Tuesday night before southerly flow brings warmer and more humid
weather Wednesday. A warm front will bring scattered showers and
thunderstorms Wednesday with a better chance for thunderstorms
Wednesday night into early Thursday with the sfc low and cold front.

A slightly cooler and less humid airmass will gradually move in
behind that system very late in the week. However a northern stream
upper level disturbance and weak sfc low pressure system will bring
potential for more scattered showers and storms late Friday into
Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 115 PM EDT Sun Aug 13 2017

VFR conditions expected through 18Z Monday.

Satellite showing high clouds streaming overhead in advance of
system currently over the Northern Plains. Cumulus cloud deck has
developed over southern Michigan this morning...with the northern
extent just now reaching Grand Rapids.

NAM and HRRR moisture profiles have picked up on the area of
moisture associated with the cumulus field and will include a
mention of scattered clouds in all TAFs through sunset. Some areas
could see broken ceilings between 4 and 5 kft AGL but given the
convective and not synoptic nature of the clouds...widespread and
long-lived ceilings are not anticipated.

&&

.MARINE...
Issued at 330 AM EDT Sun Aug 13 2017

Waves continue to subside this morning with the Port Sheldon and
South Haven buoys measuring 1 footers and the Cook Nuclear Buoy off
of Bridgman indicating 3 footers. High pressure moving in today will
result in light winds with a further dampening out of the waves. We
are essentially looking at waves of less than one foot from this
morning right into Tuesday. So after a wavy Saturday the next three
days (Today-Mon-Tues) look quite nice on the big lake.


&&

.HYDROLOGY...
Issued at 1136 AM EDT Sun Aug 13 2017

Rivers continue to run near or below normal. There is little or no
immediate concern for flooding.

Chances for rain continue to show more promise in the second half
of the work week. Amounts are questionable given the differences
in guidance. At this time, long term forecast rainfall amounts
are highest west of Lake Michigan with 1+ inch totals most likely
over Wisconsin, trending lower as the crow flies east.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...Laurens
AVIATION...MWS
HYDROLOGY...JAM
MARINE...Duke