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Area forecast discussion 
National Weather Service Grand Rapids Michigan
325 am EDT Tuesday Jul 22 2014

Latest update...
synopsis/short term/long term/marine

Synopsis...
issued at 325 am EDT Tuesday Jul 22 2014

It will be very warm and quite humid today. A cold front will
bring scattered showers and thunderstorms late this afternoon
and tonight. A significantly cooler and drier air mass will
move in behind that front for middle to late week.

&&

Short term...(today through thursday)
issued at 325 am EDT Tuesday Jul 22 2014

Our primary short term forecast challenge is to determine
convective/severe weather potential this afternoon through tonight.

It will be hot and humid today with some sun and strong south-southwest flow
warm air advection helping to boost maximum temperatures into the 85 to 90 degree range this
afternoon with dew points reaching the middle to upper 60s. We expect
severe convection over Minnesota and extreme northwest WI early this morning to
track across far northern WI and the u.P. This morning. However that
activity will stay well to the northwest of our forecast area.

However we expect a few showers and thunderstorms to develop over our
far northwest forecast area by late afternoon as the cold front moves into that
area. The cold front will then move quickly across the rest of our
forecast area during the middle to late evening hours bringing scattered
showers and storms.

Isolated strong to marginally severe storms are possible mainly
early to middle evening coincident with peak or near peak instability
with potential for sb/ml cape values to briefly reach up to as
high as 2000 j/kg for a small portion of our southwestern forecast
area. Short range guidance has also trended faster with frontal
timing the past 24 hours which is also potentially more favorable
for a few stronger storms. The most likely time frame for
convection is from around 23z this evening through 05z Wednesday
as suggested by 00z 4km NSSL WRF and latest hrrr sim z guidance.

However it is noted that 0-6 km bulk shear is weak and mainly only
around 20-25 kts off latest sref guidance... although very briefly
higher values are noted over our far northwest forecast aera. Upper level
support for more organized convective development passes by well
north of our forecast area. Instability is forecast to diminish rather
quickly from middle to late evening. So the overall threat for severe
weather late this afternoon through the late evening hours is rather
low/marginal.

It will be breezy and much cooler/drier Wednesday with maximum temperatures
only reaching the 70s. Skies will clear Wednesday night as high
pressure builds in from the northwest. High pressure will produce mostly
sunny skies Thursday with maximum temperatures in the middle to upper 70s.

Long term...(thursday night through monday)
issued at 325 am EDT Tuesday Jul 22 2014

The main challenge with the long term forecast is the shower and
thunderstorm potential over the coming weekend. Guidance continues to
suggest that the primary corridor of heavier mesoscale convective system activity will be
southwest/south of Michigan Friday through Sunday... from eastern Iowa
to Indiana. However we may still be impacted by the northern periphery
of these convective complexes with periods of showers and scattered
thunderstorms...aided by weak shortwaves in the fast west/northwest flow aloft.

A rather potent looking shortwave is prognosticated to drop down from the
northwest Sunday night and Monday... and the GFS/European model (ecmwf) are in good
agreement on this feature. Best probability of precipitation will exist during this
period... followed by high confidence below normal temperatures
behind this system for most of next week.

&&

Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1125 PM EDT Monday Jul 21 2014

Haze will be on the increase as a humid airmass spreads in from
the west tonght and Tuesday. While the upstream thunderstorms are
forecasted to weaken as the track through WI tonight...the chance
of them making it to Michigan is not zero. They will have to be
monitored overnight. A better risk for storms and impacts exists
generally after 22z on Tuesday. A cold front will be nearing from
the northwest then.



&&

Marine...
issued at 325 am EDT Tuesday Jul 22 2014

A Small Craft Advisory and beach hazards statement continues in
effect from Grand Haven northward today. Wave heights should reach
3 to 5 feet with highest waves within that range anticipated north
of kmkg up toward the points. Strongest winds/highest waves will
occur from middle morning through middle evening.

Another small craft and beach hazards statement will eventually
be needed for Wednesday for strong northerly flow behind the cold
front. The highest waves Wednesday will occur south of Grand Haven.

&&

Hydrology...
issued at 334 PM EDT Monday Jul 21 2014

Widespread significant rainfall looks unlikely Tuesday night and
Wednesday. Generally we are expecting a quarter to three quarters
of an inch of rainfall with higher amounts possible in heavier
thunderstorms. Not all locations are expected to receive rainfall
with this cold front. With a fairly quick moving line of convection
along the front...flooding is a greatly mitigated threat. Rivers
have been falling steadily and aside from a temporary bump in some
levels on Wednesday this trend should continue for the rest of the
week.

&&

GRR watches/warnings/advisories...
Michigan...Beach hazards statement from 10 am EDT this morning through
this evening for miz037-043-050.

Lm...Small Craft Advisory from 10 am this morning to 11 PM EDT this
evening for lmz847>849.

&&

$$

Synopsis...Laurens
short term...Laurens
long term...Meade
aviation...mjs
hydrology...Hoving
marine...Laurens

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