Weather

282 
fxus63 kapx 112005 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
345 PM EDT Sat Oct 11 2008 


Synopsis.../issued at 345 PM/ 


High pressure over the northeastern quarter of the country will hold 
fast into the early part of next week...ahead of an expansive and 
slow moving storm system over the western and central states. 
Eventually the western system will accelerate northeast and push a 
cold front across the western lakes in the Tuesday time frame. 
Prior to that...however...a dry and very mild period for middle October 
is in store through Monday afternoon. 


Jpb 


&& 


Short term.../issued at 345 PM/...tonight 


Main concerns are the winds and the fog. Since they are related, 
i'll tackle the winds first. Using the 1000mb geographic wind as some 
guidance for decoupling, the wind speeds are 10 to 15 knots 
overnight, so there will be some decoupling with the lower points in 
the forecast area being sheltered enough to completely decouple and 
the hilltop regions to have some wind to stay warm. So have tried to 
model that as best as possible with the areas in NE lower seeing 
more decoupling, being that they have less gradient to begin with. 
So based on that, there will be some areas that see fog, couple that 
with the light influx of moisture, will see fog across the region. 
It just that it might be in more areas east of I-75. I used the ups 
fog tool as a start based on the radiational cooling, then added 
more fog, based on the increase in moisture. 


Lutz 


&& 


Long term.../issued at 345 PM/...Sunday and beyond 


Sunday...high pressure/anticyclonic flow will predominate for Sunday 
through Sunday night. Expecting an increase in higher clouds over 
today...with clouds thickening up across the north Sunday night. 
Afternoon highs Sunday expected to be in the 70s most areas... 
averaging around 15 degrees above middle October normals. 


Monday...as upper low over the western mountains begins to open up 
and head eastward...guidance has been trending more toward what the 
European model (ecmwf) has been showing the past couple of runs...which is splitting 
the trough and allowing a piece of energy to hang back over the 
southwest while the northern branch heads into eastern Canada. 
Issues for Monday will mainly center on timing of approaching 
northern branch energy and associated cold front. Interesting to 
see the 11/00z European model (ecmwf) trend back toward previous runs of the GFS with 
a slower eastward progression of the northern branch wave...while 
the GFS now trending toward earlier runs of the European model (ecmwf) which was 
quicker with the northern branch energy (and thus pushing the cold 
front through the state earlier tuesday). Current consensus is to 
disregard the GFS for the time being and see what later trends 
bring...makes more sense that front would have a hard time pushing 
into such a persistent low level ridge. So Monday looks to be 
shaping up to be another warm and dry day...probably with a lot of 
middle/high cloud hanging around. Strong thermal gradient associated 
with front and resultant frontogenetic forcing...and a lack of 
instability ahead of the boundary suggests much of the precipitation 
will be Post-frontal. Will allow for scattered development ahead of 
the front across eastern upper/northwest lower late Monday night... 
keeping most of northeast lower dry until Tuesday. 


Extended range (tuesday through saturday)...much of the longer range 
period looks to be dominated by generally low amplitude mean flow. 
As mentioned above will maintain a slower trend with the approaching 
cold front and upper level energy Tuesday...discounting the faster 
flip-floppy GFS for the time being. Current wet forecast for Tuesday 
still looks fine at this point as front crosses the forecast area. 
Beyond that cooler air then spills back into the state for the 
midweek period...but there are some detail differences regarding 
short waves moving through the generally zonal flow and evolution 
of southern branch wave. Will probably keep the majority of the 
forecast area dry for Wednesday...though admittedly that is pretty 
uncertain at this point. With the implication of a second push of 
cool air dropping 850mb temperatures below zero by Thursday...may 
eventually need to start considering potential for lake induced 
clouds/ precipitation. Will carry a chance of rain for Friday though the 
details are a bit muddled...and start Saturday dry. Much of this 
is subject to change as the days progress as a lot of little 
details need to be worked out. As for temperatures...Tuesday may 
still turn out to be a mild day depending on cold front timing and 
cloud cover ahead of it...but readings should then drop off for 
the rest of the week. 


Jpb 


&& 


Marine.../issued at 345 PM/ 


Nice southerly gradient in place over the lakes tonight through 
Monday. Will be pretty stable however given warm air mass in place 
over the region...so not anticipating headline issues until perhaps 
Monday night as choppy waves may require small craft advisories. 


Jpb 


&& 


Aviation.../issued at 200 PM/...valid for 18z tafs 


Main concern will be the fog overnight. With light south to 
southeast winds overnight, apn and pln will probably first radiate 
and begin to fog, but then as seen this morning with the increase 
in moisture overnight the fog will continue at the sites until 
early in the morning. Tvc probably will remain MVFR as the 
downslope will help to dry and warm the air mass. 


Lutz 


&& 


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


&& 


$$