Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
745 am EDT Friday Oct 31 2014

Latest update...

issued at 328 am EDT Friday Oct 31 2014

Low pressure will deepen and move east today with a strong cold
front moving through. Winds will increase and cold air will rush
in. Rain showers this morning will mix with snow this afternoon
with windy and cold Halloween weather this evening.


Short term...(today through sunday)
issued at 328 am EDT Friday Oct 31 2014

No changes to the Wind Advisory. Upstream observation across Wisconsin
at 07z show gusts from 25 to 32 knots in the strong pressure
gradient and this area will be across lower Michigan later today
when some boundary layer mixing will allow some stronger winds to
reach the surface.

Not expecting much quantitative precipitation forecast today. A batch of showers associated with
secondary cold front is moving across the forecast area at this time with
scattered rain and show showers back in Wisconsin and the Michigan
Upper Peninsula. These should fill in this morning as sharp upper
trough axis digs across lower Michigan and 500 mb low cuts off.
Although the thunder threat today is deemed low enough to omit
from the forecast...steep lapse rates will allow any surface heating
to produce some updrafts this afternoon. So there could be some
heavier showers of snow or graupel that would whiten the ground in
a few spots...especially the High Ground up north.

Snow showers should wind down by this evening as the trough axis
moves east and lake effect snow and rain moves offshore as flow
GOES north and northeast. Quiet but cold weather to follow over
the weekend as surface ridging builds in.

Long term...(sunday night through thursday)
issued at 328 am EDT Friday Oct 31 2014

We are watching a couple of potential frontal systems that could
producing minor impacts to the area. One comes in during the Monday
night and Tuesday time frame...and the other comes in during the Wednesday
night and Thursday time frame.

The long term will start out quiet with strong upper ridging in
place across the area. As this slips east of the area...we will see
the influence of a trough currently offshore of the western U.S. Coast.
This trough will translate across the northern portion of the
country...and move through lower Michigan late in the day on Tuesday.
This will give the area a decent shot of some rainfall.

We will see a break in the unsettled weather then for Tuesday night and Wednesday.
Short wave ridging will move across the area bringing dry and
seasonable air to the area. The next chance of rain will come Wednesday night
and Thursday. A jet streak coming in from off of the Pacific will help to
dig another trough across the area. This trough will not be as far
south...and will not have a good moisture feed ahead of it until the
trough is east of the area. This system justifies having a chance of
showers with its passage... however the chances will be kept low for
the time being.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 745 am EDT Friday Oct 31 2014

Rain and snow showers will bring widespread MVFR conditions with
areas of IFR into the afternoon before the storm pulls away and
conditions improve to VFR tonight. North winds will gust to 35
knots or greater at times today.


issued at 328 am EDT Friday Oct 31 2014

No changes to the Gale Warning. Expect north gales along the
nearshore today and this evening with some gusts to 40 knots. Surface
high building in late tonight and Saturday should result in quick
decrease in winds and waves and conditions becoming fairly calm by
Saturday evening.


issued at 328 am EDT Friday Oct 31 2014

Quantitative precipitation forecast through the weekend should be too light to have any effect on
the rivers.


GRR watches/warnings/advisories...
Michigan...Wind Advisory until 2 am EDT Saturday for miz037>040-043>046-

Lm...Gale Warning until 5 am EDT Saturday for lmz844>849.



short term...ostuno
long term...njj

National Weather Service Glossary of Abbreviations