Weather

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Area forecast discussion 
National Weather Service Gaylord Michigan 
710 am EDT sun Sep 7 2008 


Synopsis.../issued at 337 am/ 


A storm system moved over central Canada overnight...before moving 
into Hudson Bay this morning. A weak surface trough associated with 
this system...moved over the northern lakes region overnight...and 
was responsible for isolated rain showers. The showers were mainly 
confined...to The Straits and east Upper Michigan. 


Lingering light rain showers...are possible over northern 
Michigan today into Monday...due to the Hudson Bay storm system. 
However the best chance of rain will be Monday night and early 
Tuesday...as a developing plains storm system...moves into the Ohio 
Valley and Great Lakes region. Swr 


&& 


Short term.../issued at 337 am/...today 


Still just enough weather out there to be annoying. Dying surface low 
just north of MQT...with SW flow ahead of contributing to a few 
showers in The Straits area and north. Land breeze convergence may 
again be a player. Reasonably strong shortwave advancing across 
Iowa...with a large shield of middle/high clouds entering our region 
from the SW. This wave will pass just to our south today. 


Much like last night...land breeze-induced showers will try to move 
into parts of northwest lower Michigan this morning (especially early). We/ll see 
lots of middle/high clouds from the shortwave to our SW...but the 
associated rain looks to stay south of northern Michigan. The next upper 
trough will near the Minnesota arrowhead this afternoon...with an associated 
cool front into western Upper Michigan and central WI late in the day. 
Showers in developing warm advection/isentropic ascent pattern out 
ahead of the front may approach the far western portion of the 
forecast are early this evening. In between...mainly cloudy but 
mainly dry. High temperatures mainly upper 60s...pushing 70 in spots. 


Jz 


&& 


Long term.../issued at 337 am/...tonight and beyond 


Shortwave trough will pass just north of the area toward dawn 
Monday...with the associated cold front almost out of the area by 
then. Another...more vigorous upper trough will move into the northern 
lakes Monday night. This will spin up a low along the front to our 
southeast...said low will move across southeast lower Michigan Monday night. 
Meanwhile...cooler air will be steadily filtering into the region. 
Precipitation trends and temperatures are the main concerns. 


Models...the GFS is preferred in being faster and more amplified 
with the strong shortwave moving into lower Michigan Monday night. 


Tonight...the models are considerably less enthusiastic about precipitation 
precipitation tonight than they were 24 hours ago. Most of the dynamics are 
now prognosticated to stay north of the border...and the cold front is not 
helpful as precipitation will be elevated. Best chance for rain will 
clearly be from The Straits area northward in the evening...where 
40-50 probability of precipitation are in order. MUCAPES near 400j/kg argue for an isolated 
thunderstorm possible...but not a substantial thunderstorms and rain outbreak. Small 
chance probability of precipitation still in order for much of northwest and north central lower. For 
overnight...some lake enhanced showers could get going in eastern 
Upper Michigan...with northwest winds...850mb temperatures lowering to +4c...and 
850-700mb relative humidity levels lingering above 70 percent. Will go dry 
overnight across the rest of the area. Low temperatures from the upper 40s 
to around 50. 


Monday...cold advection will bring cooler and (temporarily) drier 
air into the region. 850mb temperatures lower to +3c over eastern Upper 
Michigan...and around +6c in northern lower...by late afternoon. Delta T/S 
thus reach the low to middle teens. But moisture is unimpressive...with 
850-700mb relative humidity levels near or less than 50 percent for most of the 
day. Will keep a chance of light rain showers in the northwest flow 
snowbelts. Late in the day...precipitation will develop rapidly east-northeast-Ward 
from Iowa...as surface cyclogenesis proceeds in northern Illinois. 
Moisture and isentropic ascent will surge northward into northern 
lower Michigan late in the day...though perhaps not quite as fast as the 
GFS indicates. Will increase probability of precipitation after 20z south of M-32 to 
40-50...it will rain in these areas but not yet convinced precipitation 
will arrive by 00z. Maximum temperatures cooler...in the 60s. 


Monday night/Tuesday...models disagree on exact location/ 
timing...but continue to agree that some parts of central/northern 
lower Michigan will see over an inch of rain Monday night. This is due to 
the deepening surface low moving through southeast lower Michigan...the shortwave 
forcing this low...isentropic ascent...and frontogenetical forcing. 
Will kick probability of precipitation to categorical in the southern zones. No MUCAPE to 
speak of around here...but the fgen response is so strong that some 
slantwise convection may spark a bit of thunder. Have added a slight 
chance of thunder to the categorical pop area...along with a heavy 
rain mention. Tuesday looks kind of raw. Widespread precipitation should be 
pretty much out the door at 12z (though it may be close). But a 
resumption of cold advection will lower 850mb temperatures to the middle and 
perhaps lower single digits c. Airmass dries out drastically during 
the morning...as high pressure builds into the Chicago area. Will 
not bring any lake effect showers into the afternoon for now...just 
in the am hours. Maximum temperatures mainly 60 to 65. 


Rest of the forecast...broad high pressure will provide a dry period 
with moderating temperatures midweek. Return flow around the departing high 
could kick off precipitation again as soon as Wednesday night...with a better 
chance in the Thursday-Friday timeframe. This is in line with the going 
forecast. 


Jz 


&& 


Marine.../issued at 337 am/ 


Little wind today. Cold front passage tonight will usher in west to 
northwest winds...with Small Craft Advisory conditions likely 
tonight on Lake Michigan outside of gd Traverse Bay. Headlines will not be 
posted yet. A strengthening low pressure system will pass to our 
south Sunday night. Northerly winds could again reach Small Craft 
Advisory levels...mainly south of Presque Isle lt and gd traverse lt. 


Jz 


&& 


Aviation.../issued at 710 am/ 


VFR. Plentiful middle and high clouds in place...as system moves through 
the southern lakes region. This cloud cover will diminish today... 
but will be replaced by scattered-broken 040-050 cumulus deck thanks to 
relatively abundant low-level moisture. An upper disturbance passing 
north of the region could bring a few showers near pln this evening. 
Otherwise clouds are expected to temporarily diminish tonight. 


Jz 


&& 


Apx watches/warnings/advisories... 
Michigan...none. 
Lm...none. 
LH...none. 
Ls...none. 


&& 


$$ 

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