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Area forecast discussion 
National Weather Service Grand Rapids Michigan
1204 am EDT Monday may 4 2015

Latest update...

issued at 330 PM EDT sun may 3 2015

A cold front will bring some showers and thunderstorms tonight.
The front will stall just south of lower Michigan on Monday and
bring chances for rain at times through next weekend.


Short term...(this evening through Tuesday night)
issued at 330 PM EDT sun may 3 2015

Timing and coverage of precipitation will be the forecast issue in the
near term. Good moisture transport and a 35 to 40 knots low level jet arrives
ahead of approaching cold front. There is also enough middle level
instability for some thunder to be embedded in the area of rain.

Showers now over northern Illinois will spread east and arrive across
the western forecast forecast area this evening and slowly
progresses eastward...not reaching the extreme southeast County Warning Area until around
12z on Monday. Good forecast consistency in the models leads to
above average confidence in the forecast of the front slowing
during Monday and eventually stalling out just south of the
forecast area. Overrunning continues across the southern forecast
area through Monday night with likely probability of precipitation across the south
decreasing to chance across the central forecast area and slight
chance or no probability of precipitation across the north.

The front remains active on Tuesday with convection riding along
it and then slowly lifts north on Tuesday night. Forecast soundings
continue to show thunder potential across the southern half of the
forecast area during most of Tuesday and Tuesday night.

Long term...(wednesday through sunday)
issued at 318 PM EDT sun may 3 2015

Above to much above normal temperatures are expected Wednesday
through Saturday due to persistent south to southwesterly flow warm
air advection. High temperatures should reach the 75 to 80 degree
range in that time frame.

The persistent south to SW flow will result in increasing moisture.
Instability middle to late week will generally be fairly weak but
sufficient enough for the development of a scattered shower or storm
at just about any time Wednesday through Saturday. However
probabilities for a shower or storm are quite low Wednesday and
Thursday due to the lack of a triggering mechanism for convective
initiation to occur and weak instability.

The relatively better chance for scattered showers and thunderstorms will
come Friday into Saturday when instability will be relatively
stronger (potentially around 1000-1500 j/kg of sb cape). This in
conjunction with dew point values well into the 50s and a forcing
mechanism coming from the approaching low pressure and weak cold
front from the west. That boundary will likely stall out in our
region resulting in continued potential for scattered showers and
storms through next weekend.


Aviation...(for the 06z tafs through 06z Monday night)
issued at 1203 am EDT Monday may 4 2015

Showers and storms should increase in coverage as we head through
the remainder of the night. By 08z or so...the precipitation
should be moving into at least the western taf sites towards Lake
Michigan. Have not brought in any predominant lower visibility/S given
the precipitation looks to be scattered. The highest concentration
of precipitation should occur between 09z and 15z...but in a
scattered nature. There will likely be a lull in the activity
after 15z on Monday. Developing instability may yield another
round of showers and storms Monday afternoon away from Lake
Michigan. This round of precipitation is of less confidence than

Ceilings will likely fall into the MVFR category between 12z and
16z and stay there for much of Monday. These MVFR ceilings may
stay in place along i94 into the evening.


issued at 318 PM EDT sun may 3 2015

Showers and thunderstorms expected tonight and into early next
week with winds and waves remaining below Small Craft Advisory.


issued at 1136 am EDT sun may 3 2015

Rivers are running well within banks and remain steady...if not
falling ever-so-slightly. Though flooding is not anticipated at
this time...the pattern becomes active over the course of the
upcoming week and we may see within bank rises.

Precipitation is expected to developed and progress from north to
south beginning late tonight. The frontal boundary responsible for
the precipitation will stall near the Southern Lower Michigan
border which will lead to some of the higher totals aligning along
and south of I-94. This front then returns north near midweek and
provides another decent shot at precipitation for central lower
Michigan during that time frame. Yet another round of wet weather
is poised to move through late in the week and into next weekend.

The main impacts would likely be minor and not really felt until we
get into the new work week. Locations that are already rain soaked
and receive any additional convective precipitation could see
minor ponding on roadways...or low lying areas that are typically
affected by heavier rain. An additional note is that we are dry now
and green-up is occurring in many locations. This will definitely
help in taking up a lot of the moisture that falls.


GRR watches/warnings/advisories...


short term...ostuno
long term...ostuno/Laurens

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