Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
758 am EDT sun Mar 29 2015

Latest update...
aviation/marine

Synopsis...
issued at 330 am EDT sun Mar 29 2015

A cold front will bring a mix of light rain and light snow late
this morning through this afternoon into this evening and it will
also become rather windy this afternoon. Some light snow
accumulations of around an inch or less are anticipated for
central lower Michigan. A clipper system will bring another round
of light snow to south central lower Michigan Monday night into
early Tuesday. Temperatures will finally moderate to near or even
slightly above normal by the middle portion of the upcoming week.

&&

Short term...(today through tuesday)
issued at 330 am EDT sun Mar 29 2015

Primary short term forecast challenges involve determining potential
for light snow later today and again Monday night into early Tuesday.

A consensus of latest short range 00z guidance continues to
indicate precipitation will develop from west to east late this morning
through the afternoon. Precipitation will begin as a mix of light rain and
light snow and may transition to a period of mainly light rain
this afternoon over our southern forecast area near to south of I-96
as thermal profiles moderate.

Around an inch or less of snow is anticipated north of I-96 with
relatively highest amounts of around an inch or so expected over
higher elevations of our northern forecast area. However impacts will
be very minimal given the light nature of precipitation and temperatures even up
north should reach the lower 40s such that some melting will
occur.

It will become windy this afternoon with frequent wind gusts in the
35 to 40 miles per hour range. A few slightly higher gusts are possible mainly
right along the Lake Michigan shoreline especially from kmkg north to
kldm. Breezy conditions will then continue through the evening.

Precipitation will linger into the evening before ending overnight. High
pressure will build in to produce fair weather with seasonably cool
temperatures Monday. A clipper system will bring light snow to south central
lower Michigan late Monday night into early Tuesday with potential for
around an inch or two of snow near to mainly NE of kgrr.

It is noted that 00z European model (ecmwf) guidance remains further south with
precipitation placement with this system and would bring potential for
light snow accumulations of an inch or two into kgrr/klan whereas
00z NAM/GFS guidance suggests the light snow would only affect our
far north to NE forecast area.

Long term...(tuesday night through saturday)
issued at 330 am EDT sun Mar 29 2015

After a lengthy stretch of chilly weather... a couple of mild
Spring-like days are likely for the middle part of next week. Highs
in the low to middle 50s are expected on Wednesday... with readings
likely reaching or exceeding 60 on Thursday away from Lake Michigan.

The main feature of interest will be a cold front extending south
from a low in southern Canada... which edges in from the west late
Wednesday night or Thursday. Scattered to numerous rain showers
will accompany this front.

The European model (ecmwf) is much slower with the surface front than the GFS and has
rain holding off until after 18z Thursday. The GFS has the rain
arriving as early as 06z Thursday and exiting already after 18z
Thursday. These timing differences in the models are critical
because if the European model (ecmwf) is correct we could see high temperatures
approach or exceed 70 degrees on Thursday south and east of GRR.

The other big difference is that the European model (ecmwf) wants to stall the front
Thursday night as a wave moves along it. The GFS is much more
progressive with the front and with the arrival of the cold dry air
behind it. If the slower ecwmf idea of a wave along the front is
correct...we could see over a half inch of rain Thursday night
into early Friday.

&&

Aviation...(for the 12z tafs through 12z Monday morning)
issued at 755 am EDT sun Mar 29 2015

Approaching cold front will bring rain showers into the area from
west to east this afternoon. Some snow may mix with the rain at
mkg and possibly GRR as well as it begins.

Ceilings/visibilities will eventually lower into the MVFR category this
afternoon. A few hours of IFR conditions are likely this evening
as the cold front is passing through. Improving conditions are
expected after midnight behind the front.

Expect moderate low level turbulence today into the evening due to
strong/gusty south to southwest winds. Speeds of 20-25 kts are
expected at the surface with some gusts to 35-40 kts. Winds at 2-3k feet
above ground level will be around 50-55 kts. The winds will gradually subside
after midnight while turning westerly.

There will be a moderate icing threat this afternoon/evening with the
rain... from roughly 2000 feet to 18000 feet.

&&

Marine...
issued at 741 am EDT sun Mar 29 2015

This section will resume on Monday March 30th.

&&

Hydrology...
issued at 330 PM EDT Sat Mar 28 2015

Rivers remain below bankfull and are holding steady or slowly
falling. Precipitation amounting up to several tenths of an
inch over the next several days is not expected to cause a
significant rise in river levels.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

Synopsis...Laurens
short term...Laurens
long term...Meade
aviation...Meade
hydrology...cas
marine...99

National Weather Service Glossary of Abbreviations