Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 200730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Mon Mar 20 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 330 AM EDT Mon Mar 20 2017

Scattered showers, and a few thunderstorms along and south of I-96,
will continue today.  The steadiest rains will be seen closer to I-
94 into this afternoon.  The precipitation is expected to exit the
region by early this evening.  Quiet weather is then expected for
Tuesday and Wednesday.  The next of rain will hold off until
Thursday night, but it appears to linger into Saturday.

High temperatures will be around 50 today and Tuesday, then cooler
days Wednesday and Thursday, mainly 40 to 45.  We will end the week
warmer again with 50 to 55 expected for Friday and into the weekend.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 330 AM EDT Mon Mar 20 2017

After a storm night with some small hail, a cold front will cross
the CWA this afternoon, bringing more showers and a few
thunderstorms.  This rain ends by early evening, leading to a quiet
period for late tonight through Wednesday.

The best jet dynamics has exited the region early this morning and
the showers and storms were weakening.  However with the front
crossing the area this afternoon we will see showers and a few
storms regenerate.  Some upper divergence moves over the southern
CWA by early afternoon too, helping support a better coverage of
pcpn there.  Enough elevated instability to expect scattered
thunderstorms too through about 21Z along and south of I-96.  there
could be a few lingering showers over the SE CWA into this evening,
otherwise the region begins to dry out.

A large area of cool and dry Canadian high pressure moves in for
Tuesday and Wednesday.  H8 temps drop to around -12C by Tuesday
night.  With the dry air mass expect a large diurnal temp swing.
Tuesday should be 45 to 50, then lows crash to 15 to 20 for Tuesday
night.  Highs Wednesday will recover to the 30s.  Despite the chilly
air, the air mass looks far too dry to support any lake effect.

.LONG TERM...(Wednesday night through Sunday)
Issued at 330 AM EDT Mon Mar 20 2017

One last cold night starts out the period with high pressure
positioned over the Great Lakes. This high will begin departing to
our southeast. As winds shift out of the south, temperatures will
gradually moderate through the day Thursday with highs returning toe
near normal.

We continue to see our next weather maker come ashore over the
southwestern conus in the same timeframe. The upper level trough
progresses eastward, developing into a closed low over the central
plains. The closed upper low, in conjunction with a deepening
surface low, will further strengthen warm air advection Thursday
night into Friday.

Showers are expected to develop late Thursday into Friday as the
warm front lifts north. The onset of the precipitation could fall as
a bit of rain/snow, but it is becoming a little suspect with web
build zero height jumping to 8-9k feet through midnight Friday.
Bufkit overview also seem to show surface temperature rising above
freezing. So we may be able to escape much or even all winter
precip...given these trends continue. High near 60 Friday are
looking more and more likely with the front lifting north of the
forecast area.

What happens beyond Friday begins to diverge with long range models.
The GFS takes the upper low further south with a weakening cold
front clearing Lower Michigan of precipitation by Sunday. This would
act as more of a slight cool down as ridging develops right behind
the system again. The ECM, however, take the upper low much further
north...right over the Great Lakes...keeping precip chances high
through the weekend. Either solution would keep temperatures near
normal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 153 AM EDT Mon Mar 20 2017

The initial concern deals with the elevated convection that is
currently pushing southeast (currently SE of KMKG) through the
area. This line has survived a bit longer than anticipated, so it
cannot be rule out that it continues through the next couple
hours. Colder temperatures have supported pea size hail in the
heaviest cells. Hence, easy ice formation also leads to vivid
lightning. Much of this should press southeast and continue to
wane through the next few hours. Momentary drops to MVFR or IFR
are possible within the heavy rain.

Beyond tonight`s convection, we will see MVFR and IFR through most
of Monday, especially at southern TAF sites. A frontal boundary
may result in a few thunderstorms from mid-morning to early
afternoon. However, chances for thunder. This will be something
that may require amendments if storms develop. IFR cigs and vsbys
are most likely running from KAZO eastward through KJXN.

The system resulting in the activity will move out by late Monday
evening. Winds shift out of the north by late evening. We should
then see improvement with gradually lifting ceilings. MVFR and VFR
conditions are expected tomorrow Monday night.

&&

.MARINE...
Issued at 330 AM EDT Mon Mar 20 2017

We will probably need a small craft advisory by Tuesday evening and
lasting through the first half of Wednesday.  Northerly winds behind
the front will cause waves to build.

&&

.HYDROLOGY...
ISSUED AT 1047 AM EDT SAT MAR 18 2017

RIVER LEVELS ARE RUNNING AROUND NORMAL TO A LITTLE BELOW NORMAL.
WITH LESS THAN A HALF INCH OF PRECIPITATION EXPECTED THROUGH THIS
WEEKEND AND THEN NO ADDITIONAL PRECIPITATION UNTIL FRIDAY, NO
FLOODING IS EXPECTED ACROSS THE AREA INTO NEXT WEEKEND. THE
PRECIPITATION NEXT WEEKEND MAY BE ENOUGH TO PUSH RIVER LEVELS UP,
BUT THEY SHOULD REMAIN BELOW BANK FULL.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...JAM
AVIATION...JAM
HYDROLOGY...63
MARINE...JK



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