578 
fxus63 kapx 211133 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
633 am 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 350 am/...today 


Broad high pressure is centered in the Ohio Valley early this 
morning. Thermally-induced troughs continue over the lakes...with weak 
ridging over lower Michigan. Skies were cloudy with stratus/fog over most 
of the forecast area...northwest Chippewa Colorado and parts of the NE lower Michigan 
coast the only exceptions. Earlier clearing trend from the west and northwest 
has slowed considerably. Cloud cover and temperatures are the main concerns. 


West 1000-850mb winds will continue to advect drier air into the 
region this morning. We/re still to have to mix out the shallow 
fog/stratus that has formed in the wake of the main mass of clouds. 
Given the pathetic late-November sun angle...that will take time. 
Will slow the clearing trend from earlier forecasts. By afternoon... 
as high pressure lifts toward Lake Erie...low level winds will back 
SW and weaken (10kt or less). This will slow the advection of drier 
air...just as it/S trying to depart the southern zones. In 
addition...the coolest low level air will linger there (850mb temperatures 
around 3c...vs 5-6c in eastern upper). Still expect low clouds to 
clear for a time around midday...but lingering moist/cool airmass 
will allow a decent cumulus field to refire (partly cloudy). 
Elsewhere...a mostly sunny afternoon is planned. 


With current temperatures still fairly mild (mainly near 40 degrees)...and 
a (hopefully) respectable amount of sun...will steer temperatures toward 
the warmer end of guidance. Thus...mainly near 50 to the lower 50s. 


Jz 


&& 


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 633 am/...valid for 12z tafs 


Widespread IFR conditions this morning in fog/stratus. Improvement 
to MVFR and then VFR is expected midday and afternoon as drier air 
moves in from the west. Fog and low clouds could return tonight... 
especially at apn...but should not be as widespread. 


Jz 


&& 


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


&& 


$$