Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Rapids Michigan
320 am EDT Wednesday Aug 20 2014

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

issued at 320 am EDT Wednesday Aug 20 2014

Skies will be partly sunny today after areas of dense fog this
morning. There is a chance of showers and thunderstorms later
today mainly east of Highway 131. A strong warm front will bring
potential for thunderstorms Thursday night with very warm and
humid conditions and scattered showers and storms expected
Friday through the weekend.


Short term...(today through friday)
issued at 320 am EDT Wednesday Aug 20 2014

Areas of dense fog will gradually develop through the early morning
hours due to gradual clearing... light boundary layer winds and
ample lingering low level moisture from the rainfall yesterday.

The fog is not dense or widespread yet. However given these
expectations for fog to become more prevalent and denser through
daybreak we will go ahead and hoist a dense fog advisory for our
entire forecast area until 15z. After fog gradually dissipates during
the middle to late morning hours skies will be partly sunny with a
chance of showers and thunderstorms mainly east of US-131 this

Dry weather is anticipated tonight although there is potential for a
few showers or isolated storms to move into our far SW forecast area
toward daybreak Thursday. There is a chance for a few showers and
storms through the day Thursday but the better chance for
convection will hold off until Thursday night due to a strong warm
front and forcing from a 25 to 35 knots low level jet. 1000-850 mb moisture
transport also ramps up Thursday night and there is potential for
some heavy rainfall.

There is still a chance for a few lingering showers and storms
into Friday but a consensus of latest short range guidance
suggests most of the day should be dry but very warm and humid.

Long term...(friday night through tuesday)
issued at 320 am EDT Wednesday Aug 20 2014

00z model guidance is in better agreement tonight and show upper
ridging across the Great Lakes during the period...which would limit
shower and thunderstorm activity despite presence of instability and
some isentropic ascent. Went with low or slight probability of precipitation every period
although chances could increase towards the end of the period with
height falls as the ridging begins to flatten and the western trough
moves east.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1242 am EDT Wednesday Aug 20 2014

IFR and LIFR conditions expected overnight as significant low
level moisture results in stratus and fog formation. Most sites by
10z-11z should see visibilities at or below 1 mile and ceilings below

The stratus and fog should gradually lift through the course of
the morning with VFR returning in the 15z t0 18z time frame.
Scattered showers are expected Wednesday afternoon...but with far
less coverage and much less intensity. Used vcsh wording for now.

VFR conditions should then prevail into Wednesday evening.


issued at 320 am EDT Wednesday Aug 20 2014

Minimal wind and wave action is anticipated today but areas of fog
will pose a hazard to mariners. Very ltitle wave action is
anticipated through the end of the week but areas of fog will
remain a possibility.


issued at 330 PM EDT Tuesday Aug 19 2014

Heavy rainfall rates of 1-2 inches per hour through early evening
will support a threat of Urban and Small Stream flooding. Scattered
nature of these heavier amounts should limit extent of rises on the
larger rivers. The pattern later in the week supports additional
heavy rainfall events so river flooding could become more of a
concern by that time.


GRR watches/warnings/advisories...
Michigan...dense fog advisory until 11 am EDT this morning for




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

National Weather Service Glossary of Abbreviations