Weather

927 
fxus63 kmqt 071119 aaa 
afdmqt 


Area forecast discussion...updated aviation discussion 
National Weather Service Marquette Michigan 
720 am EDT sun Sep 7 2008 


Discussion... 
the main concern with this forecast package is the potential for 
rain showers and thunderstorms today and tonight. 


Water vapor imagery and RUC showing a longwave trough over south 
central Canada and a ridge along the Canadian Pacific coast. 
Shortwaves sweeping through the base of this trough are over 
southern Manitoba...northern lower Michigan...and middle Mississippi 
River valley. Surface analysis depicts a low over northern Ontario 
with a cold front draped southwest through Minnesota into Nebraska. 
A high is pushing in from south central Canada. Showers and 
thunderstorms have been firing over Iowa and southern Wisconsin and 
over southeast Manitoba and northwest Minnesota in response to the 
shortwave instability. Low level moisture ahead of the frontal 
system have contributed patchy fog around the area this morning. 


The shortwave over Manitoba will sweep into boundary waters area of 
northern Minnesota today...while the shortwave over Wisconsin will 
lift northeast through lower Michigan while the Iowa shortwave 
shifts into the u.P. Meanwhile...the cold front will sweep into 
central u.P. Isentropic ascent associated with the frontal system 
and q-vector convergence with the shortwave energy will slide 
through the area today. Bismarck soundings tonight was moderately 
dry below 750mb and near saturation above. Forecast soundings 
pointing to low level dry conditions continuing through this 
morning. Conditions look favorable for chance of showers and 
thunderstorms today. Radar already picking up some isolated activity 
over Wisconsin. The local high resolution models support the current 
timing on the precipitation spreading into the area. 


A middle level weak low sweeping through the base of the longwave 
trough will shift to just north of Wawa tonight drawing a weak 
shortwave across the forecast area. A weak shortwave accompanying 
this trough will shift over central and eastern u.P. The cold front 
will eastern u.P. By midnight. A light drier air will invade the 
area from the west behind the front with a weak surface high. 


A little deeper shortwave sweeping through the base of the Hudson 
Bay low will pass over the forecast area on Monday. A surface low 
will lift out of the Central Plains across Southern Lake 
Michigan...while the high builds over the northern plains and the 
upper Mississippi River valley. The European model (ecmwf) is keeping dry air over 
the forecast area on Monday with the high spreading over the 
area...while the GFS is considerably moist in the low levels. Will 
favor a compromise between these two. Thus looking for shower and 
thunderstorms remaining over the area...mainly over the south. 
Forecast soundings show that an inversion will be over the area 
around 875mb...and dry below 900mb. By sunset the inversion will 
lift to around 700mb and the air mass will start to saturate. The 
wet bulb zero level will be around 5.5k feet by late 
afternoon...favoring small hail development. 


The shortwave will finishing passing over the forecast area Monday 
night. The surface high will edge into the forecast area. Thus plan 
to dry out conditions for Tuesday and Tuesday night. The next system 
will approach the area late on Wednesday. 


&& 


Aviation (for the 12z taf issuance)... 


VFR conditions expected at both sites through today. By late in the 
evening...MVFR with some fog or MVFR ceilings will form due to rain at 
both sites. Things should not get out of hand as a west wind is 
downslope at ksaw. Fog will advect in from Lake Superior into kcmx. 
Think with the stronger winds...should not get out of hand there 
either. 




&& 


Marine (for the 4 am Lake Superior forecast issuance)... 


Winds will pick up today as a cold front moves across Lake Superior 
tonight and will increase to up to 30 knots tonight. A low will form 
over northern Illinois Monday evening and deepen as it moves into 
western Quebec on Tuesday. Look for high pressure to build over the 
Central Plains and Minnesota Tuesday afternoon and move to the 
eastern Great Lakes Wednesday evening. A low pressure trough... 
extending from western Ontario to the Central Plains Wednesday 
evening...will Cross Lake Superior Thursday. No gales forseen 
anytime soon. 


&& 


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


&& 


$$ 


Discussion...dlg 
aviation...GM 
marine...GM