Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
638 PM EST Tuesday Nov 24 2015

Latest update...

issued at 311 PM EST Tuesday Nov 24 2015

One more dry day is in store before light rain moves in Wednesday
night. Looks like a wet Thanksgiving is in store with steadier
rains expected Thursday night into Friday morning. Fair weather is
expected later Friday into Saturday. A light mix of rain and snow
is a possibility for Sunday...with rain showers once again a
threat heading into Tuesday.


Short term...(this evening through Thursday night)
issued at 311 PM EST Tuesday Nov 24 2015

Primary focus continues to be on expected rainfall from Wednesday
night through Thanksgiving. A 40 to 50 knot low level jet at 06z Thursday
should help transport low level moisture into lower Michigan early
Thursday morning. All the models show some light rainfall
developing during this time. is not until after 18z
Thursday when the strongest upper level forcing arrives as h250
divergence approaches the Great Lakes.

The greatest risk for one inch or more of rainfall appears to be
near/north of I-96 and also for areas west of US 131. Our model
blended quantitative precipitation forecast features between one and one and a half inches for
these regions...with less rainfall expected elsewhere as the surface
cold front will be progressing fairly quickly across our southeast

In the absence of convection...the highest rainfall amounts
should be fairly close to the going forecast. At this time...we
are not overly concerned about flooding in spite of a snowpack
presently covering at least the southern half of the County Warning Area. That
said...we could see some rivers approach or exceed bankfull with
a completely melted snow pack along with the expected rainfall.
Please see Hydro section and/or the hydrologic outlook product for
more details.

Outside of the rainy Thanksgiving Holiday...a dry Wednesday is in
store with breezy conditions expected for the Lake Shore counties
as southerly flow increases out ahead of the cold front.

Long term...(friday through tuesday)
issued at 311 PM EST Tuesday Nov 24 2015

The slow moving frontal boundary will continue to bring rain on
Friday that will gradually taper off from north to south Friday
afternoon and evening. A high pressure ridge will then gradually
build in from the west to bring fair weather Friday night through
Saturday night with seasonable temperatures.

A low pressure system tracking slowly NE from the lower Ohio Valley
region will bring a small chance of mixed light rain and light snow
showers near to mainly south of I-96 Sunday. The light precipitation shield
will shift a little further north such that all of our forecast area
will have a chance for a mix of light rain/light snow showers Sunday
night and Monday.

Beyond that the main low pressure system should move through Tuesday
and bring some rain showers Tuesday into Tuesday night before high
pressure builds in to bring fair weather for middle to late next week.
Southerly flow early next week will help to boost maximum temperatures well
into the 40s before cooler air moves back in behind that system for
middle to late week.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 637 PM EST Tuesday Nov 24 2015

We/re likely to see some fog again tonight...mainly after 04z and
be mostly in the MVFR category. It/S possible though that IFR/LIFR
could develop in Jackson where there has been more snow melt and
thus more low level moisture available. Not really confident on
that though and held the visibility at 2sm overnight.


issued at 311 PM EST Tuesday Nov 24 2015

Small Craft Advisory issued for all but the southernmost zone from 09z Wednesday through
Thursday night. South flow increases ahead of the cold front with
some gusts to 30 knots possible. Could need to upgrade our
northernmost zone to a Gale Warning depending on latest model
data. Headlines may be needed right on through Friday with a north
flow event developing.


issued at 1257 PM EST Tuesday Nov 24 2015

The current snow pack is expected to completely melt off by the
end of the week. The greatest depth is near and east of I-69 where
4 to 8 inches of snow is on the ground. The water content of the
snow pack in this area ranges from a few tenths of an inch to
approaching one inch across southern Jackson County.

Forecast rainfall amounts of one half to one inch or possibly
greater will fall from Wednesday night through Friday.
However...the greatest amounts are expected to occur northwest of
the hardest hit areas from this past weekend. This could possibly
change so continue to monitor updated forecasts.

Rivers will begin rising as the snow melts and the rains occur.
Current River forecasts are beginning to incorporate some of the
anticipated snow melt...such as the Sycamore Creek at Holt. Future
river forecasts will start including the expected rainfall over
the Thanksgiving Holiday and it is possible that some small rivers
and streams could reach or exceed bankfull.

Refer to the National Weather Service Grand Rapids advanced hydrologic prediction
service at http://water.Weather.Gov/ahps2/index.Php?Wfo=grr for
more information.


GRR watches/warnings/advisories...
Lm...Small Craft Advisory from 4 am Wednesday to 7 PM EST Thursday
for lmz845>849.



short term...Hoving
long term...Laurens

National Weather Service Glossary of Abbreviations