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Area forecast discussion
National Weather Service Grand Rapids Michigan
728 am EDT Wed Jun 26 2019

Latest update...

issued at 330 am EDT Wed Jun 26 2019

- warm and dry today.

- Seasonal warmth and increased humidity into next week.

- Occasional storms Thursday into next week, some may be severe.


Discussion...(today through next tuesday)
issued at 330 am EDT Wed Jun 26 2019

With the subtle shortwave now departing, it should be a relatively
pleasant Summer day amid height rises and weak subsidence. Drier air
at 850 mb will mix down today and knock dewpoints down into the 50s.
Highs won't be too far from late June normals, so that will feel
relatively warm for this year so far. Any thunderstorms will likely
stay south of the area but won't be too far off in Indiana.

An active pattern is setting up for at least Thursday through
Saturday if not into part of next week also. An upper-level ridge or
ring-of-fire anticyclone will build into the Central Plains over the
next few days. While models sometimes overdo it days in advance,
elevated mixed layers advecting from the intermountain west may make
greater inroads toward Michigan than what has been common this
Spring. As a result 700-500 mb lapse rates between 7-8 k/km would
boost cape values substantially from time to time. At 850 mb, flow
tendency from the southwest will occasionally transport moisture
underneath the steeper lapse rates, resulting in thunderstorms in
any areas where lift is present.

The next time frame of concern will be Thursday or Thursday night
as a convectively enhanced shortwave moving through the ridge
across the upper Midwest approaches. 2000 j/kg of cape is possible
along with 30 knots of deep-layer shear, supporting tall updrafts
and perhaps some organized internal storm dynamics. An Storm Prediction Center
marginal risk is in place for this environment, but the mesoscale
details will not become apparent until later. Models also have a
tendency to underpredict the southward extent that mcss will
propagate toward in this pattern, which is another consideration.

We have quite a few days with 20-40 pop in the next seven days, as
this large scale pattern may continue, but day to day chances of
storms will be governed by the mesoscale picture left behind by
the previous day's events. The lowest chance of storms appears to
be Sunday as the Hudson Bay upper level low is kicked toward New
England, which may give US a backdoor cold front and stabilize US.
After that, model ensembles diverge but a number of solutions
bring back roughly the same pattern as before.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 728 am EDT Wed Jun 26 2019

VFR conditions will continue through tonight. West winds around 10
knots with some gusts near 20 knots this afternoon will go light
and variable tonight.


issued at 330 am EDT Wed Jun 26 2019

Winds and waves should be fairly tame the next few days except for
around occasional thunderstorms which restart Thursday. Can't rule
out some areas of fog Thursday into Friday as humid air rolls back
over the 55-60 degree waters.


issued at 330 am EDT Wed Jun 26 2019

Rivers are still running high following the heavy rain last
Thursday, but all have crested and are now receding. The storms
yesterday are not expected to have an impact on this trend.
Occasional storms in this potentially active pattern over the next
week could produce local flooding of roads or smaller rivers if
they repeat over the same location. Tolerance for sustained heavy
rain is reduced due to the wet soils and High River levels.


GRR watches/warnings/advisories...



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