752 
fxus63 kapx 071745 
afdapx 


Area forecast discussion 
National Weather Service Gaylord Michigan 
1245 PM EST Wednesday Jan 7 2009 


Synopsis.../issued at 340 am/ 


A strengthening storm system will lift through the eastern Great 
Lakes today and into upstate New York tonight. Occasional snows will 
continue to affect all of northern Michigan through the day and at 
least the evening. Light amounts of snow will fall...however a few 
areas will see heavier amounts. While the storm exits to our east 
late tonight...lake effect snows will continue to affect the 
snowbelts. These snows will persist through Thursday night with 
additional accumulations anticipated. The snow will taper off late 
Thursday night and Friday...before an Alberta clipper will quickly 
arrive Friday afternoon for potentially more accumulating snow. 


Smd 


&& 


Short term.../issued at 1115 am/...this afternoon 


High amplitude trough axis working eastward into the Great Lakes 
this morning with various embedded short waves noted on water vapor 
imagery. Attending surface low continues to deepen slightly this morning 
(988 mb) while swinging northeastward toward Toronto. But as 
anticipated...main Gulf moisture feed with this system has been 
shunted into the middle Atlantic/New England region. Across northern 
Michigan...middle level thermal gradient a bit tighter than expected 
this time yesterday and ultimately did bring a few hours of f-general 
induced banded heavier snowfall across a portion of northwest lower 
Michigan overnight (around 3 inches reported in the Lake Leelanau 
area). That has since diminished but have also seen a couple rounds 
of more convective looking heavier snow slide up through the Saginaw 
Bay area/NE counties overnight and this morning...which lines up 
nicely with NAM depicted pocket of 6-7c/km middle level lapse rates 
sliding up across Lake Huron. But thus far not much in the way of 
lake enhancement up the Huron coast with apn checking in with less 
than 1 inch of snow through 7 am. 


This afternoon through tonight...surface low expected to slowly work 
it/S way into New York state by evening while low level flow backs 
to north by evening and north-northwest overnight. Weakish middle level deformation 
("wrap around") forcing and overall light synoptic snowfall will 
likely persist but further diminish through the afternoon as the 
middle level circulation heads into Ontario. But on the whole...cant 
see much more than an inch of total daytime synoptic accumulation 
for most areas. Maybe a little better along the NE lower Michigan 
coastline as low level temperatures cool further and with flow coming off 
Lake Huron. May also do a little better in the Grand Traverse Bay 
region later in the day as flow turns into the north. But given what 
has occurred thus far and what is expected going forward...cant 
justify keeping Presque Isle/Montmorency/Alpena counties in an 
advisory especially since other areas have seen more snow. Thus will 
cancel that advisory. Am a bit concerned for areas west of US-131 
later tonight through Thursday as north-northwest flow lake effect parameters 
not looking too shabby although instability could be better. 
Nonetheless...advisory type snowfall looking like a good bet but 
will mull this over for the afternoon forecast issuance. 


Adam 


&& 


Long term.../issued at 340 am/...tonight and beyond 


Biggest challenge revolves around lake effect chances through Thursday 
followed by additional snow chances heading toward the weekend as a 
series of clipper systems drop into the Great Lakes. Expect 
lingering light snow across the region to slowly dissipate through the 
late evening/overnight hours as brief shot of deformation dynamics 
weakens...only to be replaced by developing lake effect snow showers 
as low level flow becomes N/NW. Parameters not too shabby with Delta 
t's around 15c while 850-700mb relative humidity well above 80% through Thursday and 
inversion heights around 800mb. However...gradual development of 
upstream anticyclonic flow regime into Thursday morning/afternoon means loss 
of initial Lake Superior connection and also some spreading out of 
snowfall. Could foresee eventual need for a headline with perhaps 
2-4/3-5 across portions of northwest lower...though confidence 
sufficiently low at this point to hold off. 


Lingering activity should slowly wind down into Thursday night as 
moisture quickly wanes and inversion heights fall to around 900mb 
with approach of shortwave ridging. However...break short-lived as 
next piece of Pacific energy on track to arrive as a clipper system 
Friday/Friday night timeframe. 00z guidance still jumping all over the 
place with regard to placement of surface response and best placement of 
precipitation shield...and given splitting nature of western system fully 
expect additional changes before system gets ashore. Will thus keep 
going likely probability of precipitation intact...with the potential for a rather quick- 
hitting modest snow event. Thereafter...a return to lake effect into 
Sat/Sat night before perhaps next clipper system arrives sometime 
sun/Monday (will leave that one for the day shift). 


Lawrence 


&& 


Marine.../issued at 1115 am/ 


On the heels of departing surface low...tightening pressure gradient 
will lead to small craft gusts/winds on the Lake Huron side through 
at least Thursday and have stretched out going advisory accordingly. 
Small craft conditions also appear likely on the Lake Michigan 
side...south of Sleeping Bear Point...and have issued a Small Craft 
Advisory for that area as well. 


Adam 


&& 


Aviation.../issued at 1245 PM/...valid for 18z tafs 


Low pressure tracking into southeast Ontario will continue to produce light 
snowfall across northern Michigan this afternoon...with overall IFR 
conditions prevailing at the terminal sites. Improvement will come 
tonight at pln/apn as synoptic snowfall winds down. However...flow 
backing to north-northwest expected to bring some heavier snow showers to the 
tvc site tonight through Thursday...with conditions teetering 
between IFR and MVFR. 


Adam 


&& 


Apx watches/warnings/advisories... 
Michigan...none. 
Lm...Small Craft Advisory from 5 PM this afternoon to 5 PM EST 
Thursday for lmz344>346. 
LH...Small Craft Advisory until 5 PM EST Thursday for lhz347>349. 
Ls...none. 


&& 


$$ 

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