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000
FXUS63 KGRR 261129
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
729 AM EDT Sun May 26 2019

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 323 AM EDT Sun May 26 2019

- Showers and a few thunderstorms south of I-96 today

- Memorial Days will start out with mostly clear skies then
  showers and thunderstorms will move toward evening

- Showers and thunderstorms Monday night into Tuesday morning with
  heavy rain the most significant threat

- A stronger system will move across the area Tuesday night into
  Wednesday with additional showers and thunderstorms

&&

.DISCUSSION...(Today through next Saturday)
Issued at 323 AM EDT Sun May 26 2019

Seems the shortwave tracking east on the southern stream jet is a
touch farther north next expected to today. So the area of showers
with a few thunderstorms is now farther north. I would expect to
see showers and a few thunderstorms near and south of I-94 today.
All of the high resolutions models now show this. There between
500 and 1000 j/kg of MU cape near and south of I-96 during the
midday hours today. Even so most of stronger storms will be south
of Michigan today. The front should stall along I-80 today keeping
the warmer and moist air south of Michigan.

Expect two periods of thunderstorms with locally heavy rain. The
first is Monday night into Tuesday as a wave on the front south of
Michigan tracks east (models have been shifting this system south
run after run since the 23rd). Then a shearing out Southwest CONUS
upper low moves into the area while a strong northern stream wave
is digging strongly south from the arctic. So that should result
in even better storms and heavy rain Tuesday night into
Wednesday.

Looking at the bigger picture we have a blocking upper high over
Greenland in conjunction with upper level ridge over the
Southeast CONUS this is also not moving anywhere in the short
term. This has resulted in periods of showers and thunderstorms
over this area for the last week or so. This patten will continue
into Wednesday before and upstream Pacific system flattens the
southeastern CONUS ridge by the end of the week.

So, the bottom line is very wet weather patten Monday night into
at least early Thursday. Temperatures will remain near normal as
the front does not get far enough north or south to push the
really cooler air south or gets far enough north to bring the more
tropical air into this area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 729 AM EDT Sun May 26 2019

Currently we have VFR cigs and vsby across the TAF sites at 1130z.
However, this will not continue at all taf sites. A wave on the
front will bring a period of showers to most of the TAF sites in
the 14z to 21z time frame. Thunderstorms are possible at the I-94
taf sites during that time, however due the uncertainty of that I
put VCTS. Once the wave on the front moves east of the area during
the mid afternoon, showers should end. Skies will clear by 00z.
Skies should for the most part be clear through the night at all
TAF sites.




&&

.MARINE...
Issued at 323 AM EDT Sun May 26 2019

With the front not moving much winds will not be all that strong
at the surface so I do not see a small craft advisory issue for
some time to come. However some marine fog is possible as
thunderstorms from time to time into Wednesday.

.HYDROLOGY...
Issued at 703 PM EDT Sat May 25 2019

Monday afternoon into Tuesday is our next opportunity for
significant rainfall as a more concentrated round of showers and
thunderstorms may bring an inch or more to portions of the region.
Additional rainfall is expected Tuesday night into Wednesday.
Generally speaking, we expect the majority of locations along
rivers to hold below flood stage but there may be exceptions
especially along the Muskegon River. Also, if models trend higher
with rain amounts then more locations may be at risk, especially
along smaller rivers and streams. There will also be the
possibility for ponding of water on roads and low- lying spots in
areas with locally heavy rainfall.


&&

.HYDROLOGY...
Issued at 703 PM EDT Sat May 25 2019

Monday afternoon into Tuesday is our next opportunity for
significant rainfall as a more concentrated round of showers and
thunderstorms may bring an inch or more to portions of the region.
Additional rainfall is expected Tuesday night into Wednesday.
Generally speaking, we expect the majority of locations along
rivers to hold below flood stage but there may be exceptions
especially along the Muskegon River. Also, if models trend higher
with rain amounts then more locations may be at risk, especially
along smaller rivers and streams. There will also be the
possibility for ponding of water on roads and low- lying spots in
areas with locally heavy rainfall.

&&

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

$$

SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...WDM
MARINE...WDM