Scientific Forecaster Discussion
fxus63 kunr 201502
Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
802 am MST Wed Nov 20 2019
issued at 759 am MST Wed Nov 20 2019
Winds are already gusting around 40kts at both krap and krca
behind the front. Expect these gusty winds to continue, especially
just east of the Black Hills, as best pressure rises are still to
our west and the mixing layer will gradually deepen.
Discussion...(today through tuesday)
issued at 304 am MST Wed Nov 20 2019
Latest analysis shows the northern stream trough currently
crossing Montana. At the surface low pressure is centered over
eastern Colorado with an inverted trough extending northeastward
into Nebraska and the Dakotas. It looks like its going to be a
busy day in the forecast seat, making adjustments to
precipitation timing and type as temperatures cool behind the
Colder air is already moving southward to the west of the trough
into northern Wyoming. As the colder air slides southward, gusty
northerly winds and areas of low stratus have developed to the
east of the bighorns indicative of what will develop over the rest
of the forecast area as the day progresses. There will likely be
some light precip developing behind the front, and without much
ice in the cloud layer aloft, the precip type may be more drizzly
at the start. Temps behind the front should remain fairly steady
at first, then slowly fall during the day. It appears that the
best chance for freezing drizzle will be across northeastern Wyoming
and northwestern SD, but there is some chance that temps could
fall near or below freezing further south on the South Dakota plains during
the day, and subsequently result in areas of freezing drizzle.
Deeper moisture should arrive later in the day and evening to
switch any freezing precip over to snow. Snow should then end from
north to south by Thursday morning. Best chance to see a few
inches of accumulating snow will be across northeastern Wyoming and the
northern Black Hills. Aside from the precip, expect gusty
northwest winds, especially on the South Dakota plains. Strongest winds
should be just east of the Black Hills.
A stretch of dry weather is then expected through the weekend.
Chilly highs on Thursday will transition to temps into the 50s
over the weekend. Next trof moves in early next week for next
chance of precip and cooler weather.
Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 412 am MST Wed Nov 20 2019
A cold front continues to push south across the region with gusty
northwest winds behind the front. Fog, drizzle, and freezing
drizzle are expected this morning into Wednesday as cooler air
pushes in. Snow will then begin moving into the area through the
day Wednesday, with widespread MVFR/IFR conditions. Northwesterly
winds will increase to 20 to 30 kts, with gusts of 30 to 40 kts,
particularly across the western South Dakota plains.
South Dakota...Winter Weather Advisory from 3 PM this afternoon to 4 am MST
Thursday for sdz024.
Wind Advisory until 8 PM MST this evening for sdz026-030-031-
Wyoming...Winter Weather Advisory from 3 PM this afternoon to 4 am MST
Thursday for wyz057.
Winter Weather Advisory from noon today to 4 am MST Thursday for