Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KGRR 241142
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
742 AM EDT Wed May 24 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 328 AM EDT Wed May 24 2017

The overall weather pattern suggests little overall change through
at least the middle of next week. We have a series of upper level
storms that move through the area between now and next wednesday
but the way they interact with the surface weather pattern will
for the most part mean only limited amounts of rainfall with
temperatures for the most part near normal. Sunshine is most
likely on Friday. The chances for measurable rain will be
greatest today east of Grand Rapids. Scattered showers are also
possible tomorrow, then scattered showers and afternoon
thunderstorms are possible over the weekend into Tuesday of next
week. At this point it no longer looks like an heavy rainfall
events over a large are is expected during this entire time
period.

&&

.SHORT TERM...(Today through Friday)
Issued at 328 AM EDT Wed May 24 2017

We have that storm that I though yesterday could bring heavy rain
to areas south and east of Grand Rapids late this afternoon into
tonight but it now appears most of the heavy rain will be well
east of Michigan. The trowal feature now is mostly east of I-69
tonight and well east of the this area by Thursday afternoon.
Similarly the deformation zone with the mid and upper level system
does not get west of I-69. Still there is a decent surface low
that that tracks from Kentucky this morning to northern Ohio by
midday Thursday. So more than likely there will be some rain over
our southeastern CWA tonight from that.

I do believe we will see showers/thunderstorms over most of our
CWA today even so. There is enough instability (1000 to 1500 j/kg
of most unstable cape) during the midday hours (EL near the
tropopause) that it would seem to me scattered thunderstorms are
likely. Due to the southerly flow from 700 mb through 200 mb I
would seem any storms should move nearly due north today. Even so
it will not be raining most of the time. I do believe most areas
should see at least a 0.05 inches of rain but some very localized
areas could see near and inch of they got under the one of the
stronger storms (precipitable water is over an inch / which is
nearly double normal).

Beyond today our system pulls off to the northeast but we stay in
the upper level circulation through Thursday evening before
shortwave ridging moves in for Friday. So I would expect more
instability showers around Thursday. With the shortwave ridge
over the area Friday we should see sunshine during the day.

.LONG TERM...(Friday night through Tuesday)
Issued at 328 AM EDT Wed May 24 2017

Southerly flow should bring us warmer air for the weekend, but then
we should turn cooler again by Memorial Day and Tuesday.  Periods of
showers will be possible much of the extended period, but there will
be times when the showers should become more concentrated.

A cold front, with a wave of low pressure along it, should push in a
period of showers and storms into the region Saturday night and
Sunday. Given the current timing in the models, the SE CWA seems the
most favored for rain.

The other more concentrated period of pcpn should occur Monday
afternoon and evening when an upper low forms over the Northern
Great Lakes and spreads showers and a few storms into the area.

Otherwise we can not rule out random showers or storms just about
any day/night, but they will be more hit and miss then the times
mentioned above.

The holiday weekend will be mild, with highs in the 70s away from
Lake Michigan.  Then as the upper low takes shape, we will likely be
cooler into Monday and Tuesday.  In fact Tuesday could be quite
chilly with H8 temps diving down to around +5C.  We may stay in the
50s for highs Tuesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 742 AM EDT Wed May 24 2017

VFR conditions prevail at all of our TAF sites except for JXN
which has 5SM in mist. I do expect and area of showers
to move northward from Indiana this morning into our TAF sites
over southern Lower Michigan after 16z. There will be enough
instability around by early afternoon that the showers should
develop into thunderstorms as the lead edge of the deep moisture
moves into our area. Bands of convective showers will move north
northwest as they moving into the I-94/I-96 area between 16z and
18z. There will be more than one band of convective showers that
will do this but it currently seems like the showers/thunderstorms
will not reach the MKG TAF site due to to much mid level dry air
over that area.

The thunderstorms will diminish to just rain showers by early
this evening and finally come to an end totally after 06z as the
deeper system moisture gets shoved off to the east.

It will not be until after sunset that there will be enough low
level moisture in the area to bring low ceiling into the area. By
06z we could be seeing IFR at most of the TAF sites. Mid level dry
air should end the showers by 09z or so but the low clouds will
resist.


&&

.MARINE...
Issued at 328 AM EDT Wed May 24 2017

There does not appear to be a strong enough gradient wind to cause
the surface winds to be strong enough for a small craft advisory
through Friday.


&&

.HYDROLOGY...
Issued at 330 PM EDT Tue May 23 2017

While many rivers across West Michigan continue to run at above
normal levels...a falling trend should continue through Wednesday.
Areas of light rain will persist through Wednesday morning but
should not impact river stages.  The rainfall event from Wednesday
afternoon through Thursday...however...is more likely to produce
significant runoff...which could produce a new round of rises on
area rivers. Latest guidance suggests that the heaviest rainfall
will occur over the upper portions of the Grand and Kalamazoo river
basins.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...WDM
HYDROLOGY...MWS
MARINE...WDM


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.