Ridging persists Thursday into Friday as warm air
advection
accelerates into the U.P. ahead of a Clipper low advecting off of the
Canadian Rockies towards the Upper Great Lakes. These warming
temperatures are projected to bring the warmest temperatures of the
period to the area, with highs getting into the lower 70s over the
west Thursday and lower to mid 70s in the south central and east
Friday. As the cold
front of the Clipper moves over Friday, we may
see some light lake-enhanced rain showers over the Keweenaw, north
central, and east. However, with high pressure over the Southeastern
U.S. cutting off Gulf
moisture from reaching the Upper Midwest,
ensemble guidance is generally keeping PWATs below 1 inch (although
some of the latest deterministic runs such as the latest
NAM and
GFS have PWATs higher). This is turn will
mean that
rainfall amounts
will be light, generally 0.10 inches or less (the LREF has only a 5
to 20% chance for greater than 0.10 inches over the Keweenaw and
east, with the highest chances over the east). In addition, with a
strong dry layer in the lower levels that needs to be overcome, it`s
possible that most of the area will stay dry Friday due to
evaporation above the surface. Therefore, rain chances will remain
around 50% or less, unless/until model guidance begins to moisten-up
the dry layer better. Surface ridging moving through Friday night
into Saturday looks to keep the area dry behind the cold
front until
a strengthening secondary Clipper
shortwave low digs into the
western Great Lakes Saturday night. This Clipper looks to bring lake-
enhanced rain showers over the east to northeast wind belts Saturday
night. We could see a wetting
rainfall in some spots over the
western U.P. Saturday night into Sunday as the European
ensemble
does highlight anomalous
QPF amounts for that 24-hour time period;
the LREF gives around a 30% chance that at least half an inch or
liquid will fall between Saturday night and Sunday over the north
central and west along Lake Superior. As the Clipper then lifts into
southern Ontario Sunday, the lake-enhanced rain transitions to pure
lake-effect in the northeast to north wind belts. While the lake-
effect
rainfall be fairly light, given that anomalously cold air
looks to stay over Lake Superior through the rest of early next
week, we could see lake-effect rain showers continue across the
north wind belts through next Tuesday. In addition, expect the
coolest/most
normal temperatures for this time of year early next
week, as high temperatures will struggle to get into the 50s. One
more thing: temperatures may get cold enough in the atmospheric
profile to see some changeover to none-accumulating snowfall over
the west half during the overnight hours Saturday night to early
Tuesday morning (15 to 20% chance that this occurs). If this occurs,
some spots in the west half could see their first snowflakes of the
season.
