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fxus63 kapx 211830 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
130 PM EST Sat Nov 21 2009 


Synopsis.../issued at 350 am/ 


High pressure centered over the Ohio Valley and Central 
Plains...will lift north into the Great Lakes today. This pattern 
will remain in control through the weekend...generating some sun 
and above normal temperatures into the beginning of next week. 


The next chance of rain will be Tuesday and Wednesday...as a storm 
system lifts north into the upper Midwest. Temperatures will remain 
above normal Tuesday and Wednesday. 


Swr 


&& 


Short term.../issued at 1117 am/...this afternoon 


Broad area of high pressure has set up across the Great Lakes and 
most of the eastern Continental U.S. With subsidence and light flow dominating. 
Trapped low level moisture under a strengthening subsidence 
inversion/light flow and low November sun angle has conspired to 
produce widespread stratus from eastern upper down through most of 
the lower peninsula. There is a wedge of drier air just upstream 
within the surface ridge axis that will make headway into the area this 
afternoon. Combined with continued "heating" of the day...do expect 
the stratus will gradually thin...a process that is already 
occurring in spots. 


So...for the afternoon update have tweaked grids to latest observation and 
trends...but do have most areas turning out partly sunny by middle to 
late afternoon...save for perhaps the S/southeast counties where thicker 
cloud cover will hold on latest. Was originally planning to lower 
temperatures based on a slower thinning stratus deck. But 16z observation coming in 
already have many spots in the middle to upper 40s in northern lower 
Michigan (still in the upper 30s in eastern upper). So high temperatures 
ranging from the middle 40s in eastern upper and upper 40s to lower 50s 
in northern lower Michigan will work for today. 


Adam 


&& 


Long term.../issued at 350 am/...tonight and beyond 


Generally uneventful weather will continue. This is not the way November 
is supposed to work around these parts...but so be it. Shortwave 
upper ridging will move overhead tonight...giving way to a lengthy 
period of deep SW flow aloft...ahead of a closed low moving into the 
Central Plains by Tuesday morning. At the surface...high pressure 
will slowly move from the eastern lakes to the maritime provinces... 
extending ridging back into the lakes region through Monday. Temperatures and 
clouds are the main concerns through Monday. 


Models...the main focus is on the surface low expected to be brewing 
in the Central Plains or upper MS valley by Tuesday. Most of the 
energy leading to this system is still well offshore of the West 
Coast. So the wide model spread (and run-to-run inconsistencies) are 
to be expected. However...all models have US in the warm sector and 
thus with just a rain event until colder air arrives as the system 
pulls out. 


Tonight/Sunday...deep airmass remains quite dry. However... 
developing southeast flow below 950mb (in a stable layer rapidly cooling 
toward saturation) will likely result in some stratus redevelopment 
in parts of NE/north central lower and eastern Upper Michigan. Both the 
NAM/GFS (and associated numerical guidance) produce some low clouds. 
The NAM is much more aggressive...almost certainly too much so given 
the initially dry airmass. Still...will need to reorient overnight 
(and Sunday morning) cloud cover for more clouds North/East and less west. 
Presuming these low clouds are not extensive...we/ll burn them off 
by early afternoon...with mainly sunny skies thereafter. Min temperatures 
in the 30s (aiming near or below guidance). Maximum temperatures upper 40s to 
middle 50s. 


Sunday night/Monday...actually very similar issues as we have late 
tonight. Shallow (sub-950mb) southeast flow will abundant dry air aloft 
will again support areas of stratus in NE lower and eastern upper 
overnight into Monday morning. That will give way to partly (or even 
mostly) sunny conditions by Monday afternoon. Better isentropic 
ascent/return flow will remain anchored over western Superior and 
surrounding areas...no significant chance for precipitation is seen this 
far east. Min temperatures 30s...maximum temperatures upper 40s to lower 50s. 


Rest of the forecast...timing the next system remains a challenge... 
and will continue to be somewhat Bland with the midweek forecast. 
However...models are in agreement in a warmer solution that slows 
down any real risk of mixed precipitation. Will go all rain Wednesday...a mix Wednesday 
night...still primarily snow on Turkey day (even that is 
uncertain...and does not look like a big deal regardless). 


Jz 


&& 


Marine.../issued at 350 am/ 


High pressure will move from the Ohio Valley...to the eastern Great 
Lakes...to the Gulf of St Lawrence over the next 4 days. Winds and 
waves will remain well below Small Craft Advisory criteria over the 
next 2 days. However...fog could continue to cause some issues on 
the connecting waterways...especially in the late night and morning 
hours. 


Jz 


&& 


Aviation.../issued at 129 PM/...valid for 18z tafs 


IFR stratus/fog done for the day at pln/tvc and will erode at apn 
by 20z...leaving a period of VFR conditions into the evening 
hours. Low stratus/IFR ceilings again possible later tonight 
particularly at apn. However...forecast soundings/slightly drier 
air overspreading the region should keep stratus/fog at Bay to 
some degree. Whatever stratus/fog develops will mix out again on 
Sunday leaving VFR conditions for much of the day. 


Adam 


&& 


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


&& 


$$