919 
fxus63 kmqt 210718 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
318 am EDT sun Mar 21 2010 


Synopsis... 


Water vapor imagery and RUC show closed lows over northeast 
Texas...and eastern Hudson Bay. A weak ridge is over the northern 
rockies. Shortwaves moving through the base of the Hudson Bay low 
are over Northern Lake Michigan...northeast Ontario...and over 
western Ontario. Surface analysis depicts a low over eastern Hudson 
Bay with a cold front stretching west across southern Canada. A 
ridge extends from a high over southern Quebec across the upper 
Great Lakes to a high near Grand Junction Colorado. A deep surface low is 
over Arkansas with a frontal system stretching northeast across the 
Ohio River valley to Middle Atlantic States. Dry air associated with 
the ridge is keeping the air mass over the forecast area dry. 


&& 


Discussion... 


The Texas closed low will move to near kjan today. The shortwaves 
over western Ontario will skirt across Northern Lake Superior. The 
surface low will shift into western Tennessee...while the Canadian 
cold front settle south into Northern Lake Superior. Dry air ahead 
of the front will continue to keep out any precipitation. The GFS 
forecast soundings suggest that some cumulus/SC may develop around 6k 
feet. Otherwise...only some cirrus will be present through today. 
Warm air advection on a southwest flow across the forecast area will 
tend to push the temperatures up into the low 50s today...except 
along the Lake Michigan shore where Cool Lake breezes off of the 
lake will tend to hold the temperatures down a bit. Maximum temperatures 
may break some old daily high records for today. 


The middle level low over Mississippi will track into northern Alabama 
tonight. A near zonal flow will set up over northern Continental U.S. And 
southern Canada. This will keep even the weak shortwave traveling 
along this flow to the north of the forecast area. The cold front 
over Northern Lake Superior will settle just a little south into 
Southern Lake Superior...andthe crossing only parts of the Keweenaw 
peninsula. A low pressure center will develop along the front over 
eastern Montana. The air mass over Upper Michigan will continue to 
be stable and dry. Under the influence of the ridge...the winds will 
be fairly light. Thus with dry conditions with mostly clear skies 
and light winds...conditions look favorable for radiational cooling. 
The temperatures cool dip into the upper teens again tonight. 


The Alabama low will reach the west end of North Carolina on 
Monday...allowing a weak trough to start to develop over the 
northern High Plains. A zonal flow will persist over the forecast 
area keeping the shortwave energy to the north and west of the 
region. The Montana surface low along with the western cold front 
will shift into the northern plains. The west end of the ridge will 
shift south ahead of the frontal system. However...parts of the 
ridge will still be over the upper Great Lakes keeping the air mass 
dry and stable. 


The middle level trough over the central Canada will continue to deepen 
Monday night as the low over the Carolinas move off the middle Atlantic 
coast. A weak shortwave moving through the base of the Canadian 
trough will reach Western Lake Superior. Surface low in the northern 
plains will move into northwest Ontario as accompanying shortwave 
drifts across the northern plains. Although DPVA/deep layer qvector 
convergence is prognosticated to arrive over the west late...the antecedent 
airmass appears sufficiently dry and sustained by low level dry 
advection through the night that deeper relative humidity/precipitation should remain to the 
west through 12z Tuesday. Areas over the interior east/south central 
should see the lowest temperatures again closer to lingering surface 
ridge axis/driest air. 


A shortwave and cold front will move into western u.P. On Tuesday 
and then sweep across the area Tuesday night. The general model 
trend has been to speed up this front. Dry air with this front will 
limit pre frontal probability of precipitation...so restricted chance probability of precipitation to the arrival 
time and just in the wake of the feature accentuated by band of 
850mb to 700mb frontal-gensis as well as late arrival of sharper 
DPVA in advance of trailing shortwave shown by the 12z GFS. This will 
call for low probability of precipitation. 


&& 


Aviation /for the 18z tafs/... 


Dry airmass through the low and middle levels will maintain VFR conditions 
at kcmx/ksaw through this forecast period. Winds are the only issue as pressure 
gradient tightens between departing high pressure ridge and cold front 
moving southeast through northern Ontario. Stronger winds will arrive late in the 
night/morning. Initially...strongest west to SW winds will be just 
above the surface...and marginal low level wind shear could develop. Daytime heating 
will then allow gusty winds to mix to the surface by middle morning at both 
sites. Expect strongest winds at kcmx with more favorable terrain 
exposure to west-southwest winds. 


&& 


Marine /for the 4 PM Lake Superior forecast/... 


High pressure over the lower Great Lakes will remain stationary 
today while a low pressure trough stays north of Lake Superior. A 
tightening pressure gradient between the features and an area of 
falling pressure north of Lake Superior will result in stronger SW 
winds to 30 kts through this afternoon in the corridor between the 
Keweenaw and Isle Royale as terrain funneling enhances the winds. 
Winds diminish tonight into Monday as a high pressure ridge arrives. 
Next chance of stronger winds comes in late Tuesday night into 
Wednesday as northwest winds reach 30 kts with some gale gusts in the wake 
of a cold front and these winds stay up through Thursday. 


&& 


MQT watches/warnings/advisories... 
Upper Michigan...none. 
Lake Superior...none. 
Lake Michigan...none. 


&& 


$$ 


Synopsis/discussion...dlg 
aviation...rolfson 
marine...007