000
FXUS63 KGRR 260725
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
325 AM EDT Tue Sep 26 2017

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

.SYNOPSIS...
Issued at 325 AM EDT Tue Sep 26 2017

One more day of record to near record highs in the upper 80s to
lower 90s. A cold front comes through the area early tonight with
only scattered showers and perhaps an isolated thunderstorm. This
will lower our high temperatures on Wednesday nearly 25 degrees
from todays values. This will only brings afternoon temperatures
to near normal values. A second cold front on Friday brings in
the truly cold air and lake enhanced rain showers near Lake
Michigan. Temperatures will by then be chilly. Another warming
trend follows by early next week.


&&

.SHORT TERM...(Today through Thursday)
Issued at 325 AM EDT Tue Sep 26 2017

The primary question for today is can we get any rain from the
frontal system tonight? It has been 17 days since Grand Rapids has
had measurable rainfall so we can use the rain. However the way
the front comes through it is really questionable if much in the
way of significant rainfall will occur with this front tonight.

As I have been saying the past few days the upper trough that
pushes the cold front through is actually being sheared out by an
upstream Pacific system. The problem is the longwave upper ridge
is still actually in place. So most of the dynamic energy goes
well north into Southern Canada with this frontal system. The
focus of the 1000/850 moisture transport is over upper Michigan
into Ontario north of Lake Huron. The axis of the low level jet is
actually north of us as the front comes through and has nearly
always been the case this year we are in the speed divergence
area of the low level jet (not a good place for significant
convection). Also model sounding show CAPE is limited at best.
There are three things through that none the less favor some
showers, we do get into the right entrance region of the jet
overnight, precipitable water is near 1.75 inches, much above
normal, and there is upper divergence over surface convergence.
So I have increased the pop tonight by about 10 percent do not
expect a widespread rain event with this front.

Behind the front Wednesday into Thursday we have shallow cold air
so expect much cooler temperatures and partly cloudy skies.

.LONG TERM...(Thursday night through Monday)
Issued at 325 AM EDT Tue Sep 26 2017

Another surge of chilly air will be pushing in with an upper short
wave by Friday.  This feature will also bring a decent chance of
showers mostly late Thursday night into Friday morning.  Some rain
is better than nothing, but it appears a quarter inch of less will
come with this system.

The chilly air, and slightly below normal temps, that moves in on
Friday will linger through the weekend with daytime highs holding in
the 60s, and nighttime lows inland in the upper 30s to lower 40s.
Some patchy frost will be possible both Friday and Saturday nights.

Warm advection commences Sunday night and into Monday as we see
surface and upper ridging sliding in.  Highs should be back to a bit
above normal into the 70s for Monday.  It should remain dry Friday
night through Monday with the ridging taking back over.


&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1219 AM EDT Tue Sep 26 2017

There will be scattered areas of fog again toward daybreak. It
seems like the I-94 TAFs stand the best chance of seeing some fog.
It may briefly go down to IFR at any one location, but for the
most part I`m expected light fog and MVFR vsbys.

Once the fog burns off by 13-14Z the rest of the day will be VFR.
A front will approach the region late, this will cause the
southwest winds to get a bit breezy to around 10 knots for MKG and
GRR into the afternoon.

The front will bring widely scattered showers and thunderstorms
after nightfall. Introduced vicinity thunder to MKG and GRR after
01Z. These will move toward the rest of the TAF sites after 06Z.


&&

.MARINE...
Issued at 325 AM EDT Tue Sep 26 2017

Small craft advisories will likely be needed Wednesday as north
winds of 15 to 25 knots build waves to as high as 6 feet.

&&

.HYDROLOGY...
Issued at 153 PM EDT Mon Sep 25 2017

Rivers are running around normal to much below normal for the time
of year. Meanwhile, the US Drought Monitor is indicating dry
conditions across Southern Lower Michigan. Rainfall is possible
Tuesday night and Thursday night into Friday but, less than a
quarter of an inch is expected. No river issues are expected into
the weekend.

&&

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

$$

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