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fxus63 kapx 212301 
afdapx 


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


Synopsis.../issued at 401 PM/ 


High pressure...will maintain its influence over the regions weather 
through Monday...as it moves from the Ohio Valley...across New 
England...and into the Canadian maritime provinces. Patchy fog will 
develop again tonight...and could be briefly dense in a couple 
spots. Sunday and Monday will be similar...with patchy morning fog 
gradually giving way to sunshine. 


The next chance of rain will be Tuesday...as a storm system lifts 
into the upper Midwest. Temperatures will turn colder behind 
this system. Some precipitation will linger into Wednesday and 
Thursday...and it could turn wintry Thanksgiving day. 


Adam 


&& 


Short term.../issued at 401 PM/...tonight 


Large area of high pressure currently parked across the eastern 
Continental U.S./Great Lakes this afternoon. Was a slow process...but middle 
November sunshine was able to mix out shallow low stratus across northern 
lower Michigan...allowing temperatures to reach the 50s. Eastern Upper 
Michigan not so lucky as shallow stratus (likely helped by weak flow 
off lake michigan) still lingers there...with temperatures only in the 
middle 40s. 


Tonight...high pressure/light winds will continue to dominate. Main 
forecast issues revolve around the redevelopment of fog/stratus. 
Fair amount of dry air mixing from aloft has knocked surface dewpoints 
down into the middle 30s to lower 40s this afternoon across northern 
lower Michigan. Given that...Don/T think we will see quite the 
widespread stratus/fog development that we had last night...although 
not Brave enough to yank it completely. So...have gone a bit more 
optimistic with sky cover this evening before bringing some stratus 
back into the picture later overnight toward morning. 


Eastern Upper Michigan is a bit more problematic as stratus has yet 
to leave. But...model relative humidity forecasts and late afternoon satellite imagery 
does suggest that stratus will thin out to some degree by this 
evening. Will play it that way for now and see how it GOES. 


Adam 


&& 


Long term.../issued at 401 PM/...Sunday and beyond 


Outside of some fog/stratus issues Sunday/Monday mornings...the main 
forecast issues for the upcoming week will revolve around the upper 
level energy moving out of the central rockies and toward the Great 
Lakes. Multitude of model differences in timing/strength of 
features...with about a 12 hour spread between the faster/colder GFS 
and the slower/warmer European model (ecmwf). Think the European model (ecmwf) is too slow given the 
lack of backside jet energy on the western edge of upper feature 
Tuesday/Wednesday and will take a blended GFS/European model (ecmwf) solution. 


Sunday-Monday...very similar issues as Friday night west/ shallow 
/sub-950mb/ moisture...relatively weak low level flow and abundant 
dry air aloft. A bit more ridging aloft and moisture not quite as 
widespread...so fog/stratus may be a bit patchier than Friday night. 
Overall...expect areas of stratus in NE lower and eastern upper 
during the overnight/early morning hours. The stratus will thin and 
break up each day...leading to at last partly sunny skies by 
midday. 


Upper system moves into the Central Plains on Tuesday...then toward 
the western lakes on Wednesday. Even with the model differences 
mentioned previously...they all agree on northern Michigan sitting 
in the warm sector of this storm through Wednesday...resulting in 
just rain /no snow/. Will raise probability of precipitation to likely for some areas 
Wednesday/Wednesday night given plume of deeper 850mb Theta-E air surging 
northward into the area along with favorable forcing. The rain may 
begin to change to snow late Wednesday night over western 
areas/higher terrain as colder air is drawn southward on the 
backside of upper low. Surface based melt layers decrease toward 
1.5k by Thanksgiving morning...which is squarely on the rain/snow 
line. 


Thanksgiving...cold air advection continues and the rain will change 
to snow across much of the area during the day /Lakeshore areas may 
remain mainly liquid/ as upstream upper level energy drops into the 
southern Great Lakes. Combo of impressive 800 mb-700 mb Omega and deep 
moisture from Gaylord west toward Lake Michigan...and will go with 
likely probability of precipitation in those areas. Will have to keep an eye on this 
system...as it has the potential to produce a sneaky winter event 
for parts of the area /accumulating snow?/. 


Rising upper heights and drier air advecting into the area for 
Friday/Saturday...resulting in quiet weather once again as a low 
amplitude ridge moves into the Great Lakes. 


Jk 


&& 


Marine.../issued at 401 PM/ 


Strong high pressure over the Great Lakes/eastern Continental U.S. Will result 
in fairly light winds/minimal waves tonight. As the high nudges 
eastward on Sunday...stronger S/SW return flow will develop through 
the day. But winds/waves expected to remain below small craft 
criteria. 


Adam 


&& 


Aviation.../issued at 600 PM/...valid for 00z tafs 


Low stratus/IFR/LIFR ceilings expected to redevelop tonight... 
particularly at apn. However...forecast soundings/slightly drier air 
overspreading the region should preclude widespread dense fog 
development. Whatever stratus/fog develops will mix out again on 
Sunday...leaving VFR conditions for much of the day. 


&& 


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


&& 


$$