Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
523 am EDT Wednesday Oct 7 2015

Latest update...

issued at 330 am EDT Tuesday Oct 6 2015

More in the way of sunshine is expected today...especially this
afternoon. This will boost temperatures to near or slightly above
normal in the 65 to 70 degree range in most areas. A quiet night is
on tap for tonight before a cold front arrives for Thursday. Rain
will develop across central lower Michigan Thursday morning
overspreading the entire area Thursday afternoon and evening. The
rain will come to an end Thursday night into Friday morning. Cooler
weather along with dry conditions are expected for Friday and
Saturday with a warming trend forecast for Sunday into Monday.


Short term...(today through thursday)
issued at 330 am EDT Tuesday Oct 6 2015

Main forecast concerns revolve around the low pressure system moving
through the Great Lakes region Thursday and Thursday night. Models
continue to rather consistent in bringing the low through the
northern Great Lakes on Thursday pushing the cold front through the
GRR forecast area Thursday evening. All areas will see rain...with
central lower Michigan seeing the highest totals closer to the low and
better dynamics.

Thunder threat still looks low with cape values running on the order
of 200-400 j/kg. Given the limited instability not expecting much in
the way of storms. Maintained a slight chance for thunderstorms
wording given meager instability. Storm Prediction Center still has the area in a
general thunder forecast. Best chances will come towards sunset on
Thursday in the western and southwest County Warning Area.

Otherwise a quiet day today with clouds clearing out to the south.
Clouds will be on the increase tonight across the north ahead of the
low. Expecting mainly dry conditions Friday with the rain clearing
out for the most part overnight Thursday night. A few showers may
linger around sunrise Friday around Jackson...but the front should
be clearing things out quickly around that time.

Long term...(thursday night through monday)
issued at 330 am EDT Tuesday Oct 6 2015

Long term period is shaping up to be tranquil with high pressure in

Fair weather expected over the weekend with large scale ridging in
place over central North America and surface high pressure in
control in the Great Lakes region. Seasonal temperatures on Saturday will
warm considerably for highs around 70 or so on Sunday. This occurs
as the jet stream meanders across southern Canada and a deep Hudson
Bay low results in robust southwest flow in the low to middle levels.
850 temperatures increase to around 14-15 c by Sunday evening.

A cold front works through lower Michigan on Monday. Model
details/consistency still need to be worked out...but will include
slight chance probability of precipitation for now. The latest Euro does feature a nice pv
maximum that propagates out of the northern rockies into the Great Lakes
region in the Monday timeframe. So the better potential for rain
would be further north...and the 12z Euro eps probs indicate 30-40
percent chance for measurable precipitation across northern lower Michigan.


Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 135 am EDT Tuesday Oct 6 2015

LIFR conditions will persist through 13z or so with very light
northeasterly winds. All taf sites remain socked in with low
clouds due to a persistent inversion. Ceilings and visibilities will remain
steady/gradually lower between 06-10z. Vlifr most likely at klan
and kjxn with the possibility of 1/4sm at kbtl as well.

Conditions will be slow to improve this morning...but MVFR looks
more likely after 15z. We should finally start to see some
clearing take place by 22z. Winds around 5 kts will turn northwest
and eventually west this evening.


issued at 330 am EDT Tuesday Oct 6 2015

Will hold off on a potential Small Craft Advisory for Thursday
afternoon and evening in southerly flow as it still does not look
like a high confidence event yet. Potentially 3-5 footers from Grand
Haven northward up the shore. It develops Thursday in the middle to
late even if we issue this afternoon it will be 24
hours ahead of the event.

A high confidence event looks to be setting up for Thursday night
into Friday in the northerly flow behind the surface low and cold
front. Looks like a solid Small Craft Advisory event with waves of
4-6 feet and winds of 20-25 knots.


issued at 522 am EDT Wednesday Oct 7 2015

River levels remain low and well within bank across the area. A
rain event is expected from Thursday morning into Thursday night
as a cold front sweeps southeast across the region. Moisture will
pool ahead of the front with precipitable water values rising into
the 1.25 to 1.50 range which will be around the 90th percentile
for this time of year. Strong 850mb moisture advection will be
seen along and ahead of the front. Current thinking is many areas
will see rainfall totals in the quarter to half of an inch range.
There is potential to see slightly higher than a half inch along
the U.S. 10 corridor across central lower and less than the
quarter inch amounts towards Jackson. Bottom line though these
values will not cause any Hydro issues given the already low
levels. Dry weather is forecast this weekend.


GRR watches/warnings/advisories...


short term...Duke
long term...ebw

National Weather Service Glossary of Abbreviations