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Area forecast discussion 
National Weather Service Gaylord Michigan
1028 am EDT sun Sep 21 2014

issued at 236 am EDT sun Sep 21 2014

Wet weather will continue in northern lower Michigan this low pressure crosses the region. Rain will diminish
during the day...and dry weather is forecast for tonight all the way
through the work week. The usual cold spots may get frost
tonight...but our weather will get warmer as the week proceeds.


issued at 1027 am EDT sun Sep 21 2014

Middle level vorticity center now spinning its way southeast into central
lower Michigan. Pivoting wrap around/deformation axis of rainfall
along the north side of the wave stretches from Northern Lake Huron
across the tip of the mitt and across the Grand Traverse
Bay...with additional precipitation filling in across west central lower
Michigan under the wave. Short wave center will advance rather
quickly into southeast lower Michigan by early afternoon and out of the
state by late afternoon. This will of course drag deformation axis
of precipitation back down through northern lower Michigan over the next 3 to
5 hours and should bring just about everyone another period of
rainfall. Accordingly...have tried to put some detailed timing
into the forecast through the afternoon.

Convection seems to have really weakened within the deformation
band of precipitation. Still a little convection down across central
lower Michigan...but for the most part it seems that thunder may
be done for the day.


Short term...(today through tonight)
issued at 236 am EDT sun Sep 21 2014

..morning showers/storms...Much cooler...

High impact weather potential: non-severe thunderstorm potential
today. Some frost potential tonight.

Pattern synopsis/anticipated evolution: rapid pattern amplification
well underway...with nhem water vapor imagery showing Stout ridging
building up the western noam coast...with subsequent downstream
troughing digging right overhead. Plenty of activity helping deepen
this latter feature...with yesterday's showers/storms producing wave
exiting stage right...all-the-while a much more robust wave is
diving into the western lakes. While main lead wave support has
ended...attendant slow moving cold front still managing to kick off
a few shower and storms south of M-32 at this early hour. Deep layer
middle and upper level response via second wave and increasingly
cyclonically curved jet structure helping drive additional showers
and embedded storms just to our west back across Wisconsin and into
Lake Michigan (some of which is starting to move back into northwest
lower). Forcing and associated rains will continue to spread
east...impacting at least the southern half of our area later
tonight into Sunday. Cold high pressure will follow...setting the
stage for some chilly readings tonight...along with possible frost

Primary forecast challenges/concerns: shower evolution and ending of
such today. Cloud trends and just how cold to go tonight.

Details: hard to ignore strong dynamics of approaching wave...and
simple extrapolation favors the most aggressive forcing sliding
across the lower peninsula this morning. Showers a pretty safe bet
for areas south of M-32 the first half of this morning...with some
embedded elevated storms even possible given respectable middle level
lapse rates and couple hundred joules/kg of 0-6km mu cape. Figuring
northern extent of rains a much harder Endeavor...with much drier
air spreading south via developing northerly flow. Areas north of
the big bridge look to remain largely dry...and will simply follow
dry air advancement and northern edge of better dynamics for a
rather sharp pop delineation for areas north of M-32 across northern
lower. Either way...rains will steadily end from west to easy later
this morning and afternoon as dynamics push off to the east...with
all rains likely ending by late this afternoon. Thanks to a
combination of clouds/rain and simple cold air will be much chillier
day...with highs mostly in the 50s...with perhaps a 60 degree
reading or two down near Saginaw Bay.

Not quite the straightforward forecast as one would hope tonight.
Difficulties lie with cloud trends...despite building high pressure.
The center of the high remains off to our west...with light north
flow expected on its frontside across our area. Combination of this
and cloud concerns make for one tricky temperature forecast as well.
Regarding clouds...strong support for low level moisture to become
increasingly trapped below subsidence inversion...with moisture
supply itself helped along by weak lake processes. Light winds
should only help the lifting and saturation cause across The
Highlands of northern lower. Have trended quite a bit more
pessimistic with clouds south of The Straits through the early
morning...keeping the more aggressive clearing across eastern upper.
Given such...have bumped up lows a touch...keeping even the favored
ice box locations mostly in the middle and upper 30s. Frost formation
looks minimal...and will simply use patchy wording in the coldest
areas...with no headlines required.

Long term...(monday through saturday)
issued at 236 am EDT sun Sep 21 2014

..dry and warmer as the work week proceeds...

Upper flow is progressive early in the work week. Upper trough
initially in the upper Ohio Valley/eastern lakes will exit to the NE
states...allowing heights to steadily rise as ridging advances
across the northern plains and upper MS valley. That ridge will move
overhead Tuesday night. At the surface...high pressure in the
Central Plains will pass just south of Michigan Monday night. This high
will get reinforced by another high moving southeast from north central
Canada...merging into a large high over New England by Wednesday
morning...though ridging will still extend back into the lakes
region. Forecast concerns are minimal.

Monday into Tuesday...not much to worry about. Will certainly be off
to a chilly start to the day on Monday. Will also have some clouds
to contend with Monday afternoon into Monday night in northern
sections. This area will see the pressure gradient tighten and warm
advection increase...north of the high just south of Michigan...and south
of a weak cold front sagging across northern Ontario. This will
result in some middle/high clouds in northern areas...and some daytime
cumulus Monday afternoon as well.

Maximum temperatures Monday will be limited by the cool start...and will be
mainly in the 60-65f range. Min temperatures will only fall back into the
40-50f range. That will help temperatures go further Tuesday...with highs
near 70/lower 70s.

Rest of the forecast...a shortwave will minor out on Thursday as it
briefly disrupts the upper ridging in place. This system is
moisture-starved...and does not appear to pose a threat for precipitation.
A 500mb high will close off over our heads Friday (not too often we
can say that)...promising dry/warm weather to close out the week and
start the weekend.


Aviation...(for the 12z tafs through 12z Monday morning)
issued at 652 am EDT sun Sep 21 2014

Some ceiling restrictions today...mainly this morning.

Low pressure is just east of osc early this morning...and will
pass just north of Lake Ontario this afternoon. Cooler and drier
air will enter northern Michigan in the wake of the low. Ongoing rain showers
will diminish this morning...and end this afternoon. Ceilings will
tend to improve with time...but most places will be MVFR for part
of the morning...and apn will be IFR. All locales will become VFR
as the afternoon proceeds.

Somewhat gusty north winds today...gradually becoming light tonight.


issued at 236 am EDT sun Sep 21 2014

After a brief break overnight...gusty north to northwest
winds will quickly develop across the big waters today as strong
upper level energy pivots across the area. Winds will slowly subside
tonight as the pressure gradient weakens. Combination of gusty winds
and choppy waters already covered by inherited Small Craft Advisory/S over many of
the nearshores...with no changes needed at this time. Looking ahead:
mostly quiet...mild...and dry conditions expected through the
upcoming week into next weekend.


Apx watches/warnings/advisories...
LH...Small Craft Advisory until 2 am EDT Monday for lhz347>349.
Lm...Small Craft Advisory until 2 am EDT Monday for lmz323-342-
Ls...Small Craft Advisory until 2 am EDT Monday for lsz321.



short term...msb
long term...jz

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