975 
fxus63 kapx 070525 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
130 am EDT Tuesday Oct 7 2008 


Synopsis.../issued at 325 PM/ 


A high pressure system over Hudson Bay will provide dry conditions 
through Tuesday afternoon across northern Michigan. Southerly flow 
ahead of an approaching surface trough on Tuesday will usher in 
milder temperatures to northern Michigan. The surface trough will 
push across northern Michigan Tuesday night into Wednesday... 
producing the next chance for precipitation across northern 
Michigan. A brief cool down is expected for the second half of the 
week...before temperatures rebound again for next weekend. Kas 


&& 


Short term.../issued at 1044 PM/...overnight 


A Hudson Bay high will continue to usher in dry conditions from the 
east through Tuesday. Some middle to high level clouds associated with 
the old deformation axis to the southwest will pinwheel into 
northern Michigan through tomorrow...progressively yielding partly 
cloudy skies from west to east. Lows tonight will be coolest across 
eastern upper and north Central/Northeast lower Michigan where skies 
will remain clear with calm winds. These areas will likely see a 
good dose of 30s overnight with perhaps some patchy frost. Farther 
west...mid/high clouds will keep lows in the 40s overnight. 


&& 


Long term.../issued at 325 PM/...Tuesday and beyond 


Tuesday night...the surface low moves up out of the middle Mississippi 
Valley and is reinforced by the 500 mb trough dropping through the 
northern plains. While the models disagree with some of the details 
the basic idea is that between 00z and 06z the rain will move into 
northwest lower and will have spread across most of the state between 06z 
and 12z. The NAM is slower with the surface low not quite as deep as the 
GFS. So have taken a middle ground with the chance probability of precipitation in NE lower, 
which the European model (ecmwf) agrees with. 


Wednesday...I did go with likely probability of precipitation in the afternoon on the east 
side of the state as both the models reinforce the surface low. The GFS 
has a curious split in the low, and looking at the quantitative precipitation forecast field makes 
ME think that there is some convective feedback in the GFS way south 
of the region by 18z. I like the nam's quantitative precipitation forecast field in this case. Both 
models are bringing things to an end by 00z so have chance probability of precipitation 
across the forecast area. 


Wednesday night...by 06z, both models have no precipitation over for 
the forecast areas, except maybe near Drummond Island, which I think 
is overdone. So have things ending west to east with everything gone by 
12z. 850 mb temperatures start to fall, but the air is so dry 
(700-500 mb layer relative humidity < 10% and 850 mb level relative humidity <50% and falling) 
that I went with skies clearing in the west overnight. 


Thursday...the clearing trend continues especially with the anti 
cyclonic curvature and the low upper atmospheric relative humidity values. The 850 
mb relative humidity remains low through 12z the next day and there are some high 
clouds depicted by the moisture maximum in the 700-500 mb layer, but 
that GOES north of east upper by 12z. 


Extended (friday through monday)...Friday, high pressure takes over the 
region and keeps the rain out through Friday night. Saturday, the 
high slides off to the east, and a weakening cold front moves into east 
upper. This works its way into northwest lower slowly. Not really impressed 
with this system. Sunday, a warm front moves up from the south and 
brings the chance for rain, especially on Sunday night. Monday, the 
low is off to the west and with the warmer air over the region will 
go with the chance for thunderstorms with the cold frontal passage. 


Lutz 


&& 


Marine.../issued at 325 PM/ 


Hudson Bay high pressure will continue to produce southeast winds through 
Tuesday. The long and continuous fetch across Lake Huron will likely 
produce waves approaching 3 feet tonight...but winds are expected to 
remain below Small Craft Advisory criteria and so will not issue any advisories for 
tonight into Tuesday. Kas 


&& 


Aviation.../issued at 130 am/...valid for 06z tafs 


High pressure over Hudson Bay will maintain VFR conditions at 
apn/tvc/pln through the taf forecast period. Mainly scattered-broken high 
clouds are expected through early this morning with a few middle clouds as 
well. Scattered high-based cumulus will develop today...with a general increase 
in middle clouds from west to east during the evening ahead of an 
approaching cold front. Winds will be out of the southeast at or below 10 kts. 


&& 


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


&& 


$$