Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Gaylord Michigan
747 PM EDT Thursday Sep 3 2015

Near term...(this evening through tonight)
issued at 343 PM EDT Thursday Sep 3 2015

High impact weather potential: not much.

Pattern synopsis/anticipated evolution: just wow! Had to take the
perfect set-up to destroy what should have been a warm Summer
day...and it indeed happened! Culprit behind this mess is cut off
and convectively agitated middle level circulation(s) rotating
overhead...itself tucked under broad and rather substantial
subtropical ridging extending from the Southern Plains into
central Canada. Widespread rain/thunder/clouds have kept
temperatures much cooler than initially advertised. Lead mesoscale convective vortex
driven showers and storms are weakening across northeast lower
Michigan...with lighter more stratiform rain/drizzle breaking out
across northwest lower Michigan within deformation axes of 800 mb-700 mb
circulations. Above system essentially going much of nowhere
tonight as larger scale flow regime remains light.

Primary forecast concerns/challenges: shower evolution tonight.

Details: not an easy forecast for sure. Distinct downward trend in
coverage and intensity of rains this afternoon...likely tied to all
instability being locked up well to our south. Overhead system
itself is weakening...with limited large scale convergence with lack
of any well defined surface boundaries. Really feel current trends
will continue...with pockets of mostly light showers pivoting back
northwest across northern lower Michigan tonight. Really not sure
about shower coverage...although do believe it should remain
somewhat limited given factors mentioned above. Not seeing much of a
thunder threat with limited middle level lapse rates and instability.
Temperatures going much of nowhere...with overnight lows in the 60s.


Short term...(friday through sunday)
issued at 343 PM EDT Thursday Sep 3 2015

High impact potential: minimal. Isolated thunderstorms may produce
locally heavy rainfall.

Primary forecast concerns/challenges: precipitation chances and

Vertically stacked upper low gradually fills over Michigan on the upper flow remains blocked with upper ridge folding
over the upper low /quasi-Rex block/. With precipitable waters of 1.65 inches but
limited instability...another "tropical airmass" type day with
plenty of humidity and scattered showers/isolated thunder. We may
see some additional precipitation enhancement through the I-75
corridor with deep east/southeast flow providing orographic support.

Confidence in the weekend forecast not that high...with residual
bagginess in 500 mb height fields as upper low gradually becomes
absorbed along the periphery of upper ridge. Continued high
dewpoints and additional shortwave energy ejecting out of the base
of the western trough...will leave the door open for additional
shower/isolated storm possibilities - especially on Saturday. Moisture
depth on forecast soundings diminishes by Sunday with ridge more
firmly in control across the area...which should finally put an end
to the shower/storm activity.

Temperatures very challenging throughout the next several days as
they will be driven largely by cloud/precipitation trends. Will
lower forecast highs for Friday /when precipitation coverage will
likely be greatest/. Highs well into the 80s to approaching 90 in
parts of the area on Sunday.


Long term...(sunday night through thursday)
issued at 343 PM EDT Thursday Sep 3 2015

A pair of cold fronts affecting the Great Lakes will be the main
concern for the extended period. The first system is set to arrive
early in the week...with guidance slowly coming toward agreement
with arrival on Monday. Finer details with arrival will need to be
worked out as it gets into the near term...but there is a
possibility of this affecting Labor Day activities. Another system
will arrive a cold front with low pressure in Ontario
moves through the region along with another system moving in from
the plains. Temperatures will cool through the period...getting to
near or slightly below normal by Friday.


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 747 PM EDT Thursday Sep 3 2015

Cloudy/soupy conditions through Friday.

Decaying upper low is sitting over lower Michigan with pockets of
showers rotating through lower Michigan. Bulk of the activity has
moved off into southeast lower Michigan at this juncture...leaving a bit
spottier showers/drizzle across northern lower Michigan. But think some
of the heavier/more widespread rainfall will rotate back up into
NE lower Michigan during the overnight hours. Either way...solid
lower cloud cover will be the rule for much of the area with
MVFR-IFR ceilings through the night. Pln may have the best chance of
eroding away some of the low cloud cover as drier air sags in from
the north. But overall...MVFR-IFR.

Friday...showery weather again although coverage may not be as
good as we saw today. Ceilings/visibilities should come up some during the
morning. But MVFR-low VFR will be the rule.


issued at 343 PM EDT Thursday Sep 3 2015

Light mostly east winds to continue through Friday as weak
low pressure centers itself across the area. Other than showers and
areas of low clouds/fog...not expecting any significant weather
impacts. Light winds are expected to continue through much of the


Apx watches/warnings/advisories...


Near term...msb
short term...keysor
long term...alm

National Weather Service Glossary of Abbreviations