Between Miles 13 and 14 of the Old Glenn Highway lies the divide separating the Matanuska and Knik valleys. It has been more defined at times but in the same place on other days. |
Several posts on this blog mention that at times the
temperature here at the house will be 10 to 20 degrees colder than in town just
10 miles away and today was no exception. Fifteen below at the house, just
about zero in town. The geography
of that circumstance has slowly been revealing itself over the years and today
a distinct border was blatantly obvious.
But first a bit of geography. That geography of the Matanuska-Sustina Borough is first
defined by two valleys, the Matanuska River Valley and the Susitna River
Valley. It has always been an
irritation that people and most of the area media refer to it as the Mat-Su
Valley or just "The Valley."
Having lived in the Upper Susitna Valley (that's where the East Pole is) where the residents take the distinction seriously, I have always tried to use "valleys" or the specific valley. Since moving here, I have discovered there is a third valley, the Knik River Valley. Each of these has distinct weather patterns. Most often, it will be coldest in the Knik Valley but with little snow and even less wind. To the west, the Matanuska Valley, in the middle, suffers hellacious wind storms and receives very little snow.
Having lived in the Upper Susitna Valley (that's where the East Pole is) where the residents take the distinction seriously, I have always tried to use "valleys" or the specific valley. Since moving here, I have discovered there is a third valley, the Knik River Valley. Each of these has distinct weather patterns. Most often, it will be coldest in the Knik Valley but with little snow and even less wind. To the west, the Matanuska Valley, in the middle, suffers hellacious wind storms and receives very little snow.
What there is usually blows away in the next wind
blasts. To the west and north, the
Susitna Valley often is warmer and it receives more snow. No mountain ranges define the
distinctions between the valleys at their lower ends and most of them are on relatively the same
plane. They are more defined by
drainages.
For instance you would have to work at it to define the
divide between the Matanuska Valley and the Knik Valley. I doubt there is 20 feet difference in
elevation along the road between the two.
Still whatever that difference is, it creates different weather
patterns.
All that is to get to the discovery recently of the actual
dividing line, a line made subtlely obvious as seen in the attached photograph
which I took today. Note to the
right of center (east) the hoar frost in the trees. And then the left (west) while there is some snow on the
branches there is little or no hoar frost.
The National Snow and Ice Center defines hoar frost this
way:
Hoarfrost A deposit of interlocking ice crystals (hoar crystals) formed
by direct sublimation on objects, usually those of small
diameter freely exposed to the air, such as tree branches, plant stems and leaf
edges, wires, poles, etc., which surface is sufficiently cooled, mostly by
nocturnal radiation, to cause the direct sublimation of the water vapor contained in
the ambient air.
At the divide, at
least two elements could create the phenomenon of the diffence on each side of
the line. One is that it is colder
to the east, which is the Knik Valley, and that most likely creates conditions
more conducive to the formation of hoar frost. The other is that it is windier to the west in the Matanuska
Valley and what hoar frost does develop is whipped off the trees.
Why bother with all this. Curiosity.
Fascination. Perhaps a need
to understand. What's next? Explore and find one spot with the calm
of the Knik Valley the warmth of the Matanuska (when the wind isn't blowing) and
the snow of the Susitna.
Perfection.