793 
fxus63 kdlh 200246 aaa 
afddlh 


Area forecast discussion...updated 
National Weather Service Duluth Minnesota 
946 PM CDT Tuesday Aug 19 2008 


Update... 
tranquil weather pattern as expected through the overnight period. 
Made only some minor adjustments on sky cover and temperatures 
tonight...lowering values a bit across The Arrowhead region as 
well as northwest WI. Current dew points only in the upper 40s across 
the interior arrowhead. Some low stratus evident on observation and 
satellite near the head of Lake Superior...as well as the tip of 
The Arrowhead. Vorticity maximum evident on WV near cyqt and light Erly 
flow off Lake Superior likely responsible for the low 
clouds...though should see them diminish as wave passes southeast and 
winds become calm. X-sections and model soundings reveal low level relative humidity 
values should remain low enough for fog and low stratus to remain 
south and east of County Warning Area overnight...though could still see patchy 
fog develop in the favored locales by dawn. 


&& 


Previous discussion... /issued 327 PM CDT Tuesday Aug 19 2008/ 


Discussion... 
current surface analysis shows a large ridge centered over the 
tip of Northern Lake Superior...with dry conditions across the 
upper Midwest. A lake breeze continues to affect the North 
Shore...and portions of the Bayfield peninsula...although it is 
certainly not as strong as yesterday. Temperatures this afternoon 
warmed to near or above 80 degrees across much of the area...but 
have remained in the 60s to low 70s near Lake Superior with the 
persistent onshore flow. 


Dry and tranquil weather will prevail tonight...although forecast 
sky cover a bit of a challenge in northwest Wisconsin. Forecast 
models continue to suggest that low clouds...mainly stratus or 
stratocumulus...currently affecting portions of southeast 
Wisconsin...will push northwest and affect the Hayward lakes area 
after 06z tonight. This appears plausible given an 
increase...albeit modest...in moisture convergence across this 
area late tonight. Have raised sky cover accordingly but suspect 
that the most widespread and persistent cloudiness may remain 
just southeast of our County Warning Area as it interacts with the ridge to the 
north...marine layer...and drier low-middle levels...as 925-850mb 
winds turn from the southeast to southwest. Otherwise....mainly 
clear skies can be expected tonight. Forecast soundings suggest 
that some patchy fog may develop in a few areas late 
tonight...but kept out of forecast for now as probability remains 
low. 


High pressure will remain in control on Wednesday with warmer 
temperatures as winds turn southerly on a return flow. While a 
lake breeze can again be expected...it should be rather 
weak...and primarily impact areas from Duluth and along the 
immediate North Shore as winds both at the surface and aloft turn 
south- southwesterly and become more bonafide. 


Clouds will gradually increase on Thursday in advance of an 
approaching trough and cold front dropping out of The Rockies. 
Strong warm air advection combined with a tightening pressure 
gradient will result in gusty winds and quite warm 
temperatures...with Thursday afternoon highs well into the 80s 
for most locales. 


While there are some differences among the models regarding the 
timing of the cold front...it appears that Friday and Friday 
night will feature the best chance for precipitation. 
Thunderstorms...some strong...are certainly possible...especially 
if the front were to progress across the area during peak daytime 
heating. But the NAM and European model (ecmwf)...and to lesser extent the 
GFS...show that an initial wave of low pressure will lift north 
out ahead of the main system...and bring a chance of rain and 
scattered thunderstorms to the eastern half of the area...mainly 
northwest Wisconsin...by late Thursday night into early Friday. 
This feature would act to reduce low level heating. 
Furthermore...quite a cap will be in place with 7h temperatures around 
10c-12c during the morning and midday hours...with the much 
cooler middle level temperatures confined to the north over Canada. 
Models also continue to keep the greatest instability separate 
from the peak deep layer shear. Still...the contribution of a 
strengthening low level jet and increased moisture and surface 
convergence will raise the risk for storms. 


The chance for thunderstorms will linger over our southeast zones 
on Saturday morning...before drier air arrives across the entire 
area on Saturday night and prevails through next Tuesday...with 
highs generally in the 70s. 


Aviation... 
VFR conditions will prevail through the afternoon and evening 
hours. A broken deck at 4-5k feet will push northeast through the 
Minnesota arrowhead...briefing affecting a line from kdlh to khib 
to kinl before 0z. Overnight...low level moisture is expected to 
spread northwest through central Wisconsin...and may impact much 
of northwest Wisconsin up to near kdlh. Confidence is not high at 
the moment...so have included a tempo mention at khyr and kdlh 
overnight for some low stratus...which may bring IFR conditions 
during the 8z to 12z time frame. Future taf issuances will 
monitor the trend of these clouds overnight. After 
sunrise...these low clouds should dissipate...if they make it 
this far north and west. Also included a mention of patchy fog at 
khib. Kinl and kbrd are expected to remain VFR throughout the 
period. 


Additonally...low level wind shear is expected overnight...mainly 
from 4z to 13z...at all taf sites...as a southwesterly low level 
jet increases...and is veered with the surface winds. 


&& 


Point temps/pops... 
dlh 54 80 62 83 / 10 10 10 10 
inl 58 85 63 85 / 10 10 10 10 
brd 61 85 64 87 / 10 10 10 10 
hyr 57 84 61 87 / 10 10 10 10 
asx 57 84 64 83 / 0 10 10 10 


&& 


Dlh watches/warnings/advisories... 


Minnesota...none. 
WI...none. 
Ls...none. 


$$ 


Lonka