Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Bismarck ND
1203 PM CST Friday Nov 27 2015
issued at 1203 PM CST Friday Nov 27 2015
We lowered highs today slightly in the Williston Basin where it
appears the low-level inversion is being slowest to weaken due to
the influence of snow on the ground. Elsewhere we generally stayed
the course with the forecast for today...recognizing that short-
range model guidance has generally been a few degrees too cold
when compared to the observed diurnal trends thus far today.
Update issued at 910 am CST Friday Nov 27 2015
Lake-induced cloud cover from Lake Sakakawea toward Harvey is
slowly diminishing and that trend is expected to continue through
midday. We updated cloud cover today based on satellite trends...
but other changes to the forecast were relatively insignificant.
Given the cold start...it/S possible that forecast highs are a bit
optimistic even with weak warm air advection aloft...so we will
need to watch the diurnal trend over the next few hours.
Update issued at 555 am CST Friday Nov 27 2015
Northern plains remains in a broad deformation zone aloft as Rex
block forms over the western US. This will maintain a region of
subsidence across the region and mainly sunny skies today.
Several local effects need to be included in the short term
forecast. Recent snow across the west have resulted in strong
overnight radiational and low temperatures have fallen to 5 and
10 below between Hettinger and Watford City and west. Wind chills
are near 20 below as well in this region. Also an area of stratus
has formed downwind of Lake Sakakawea. This area is moving east
southeast toward Jamestown. Do see any snow on radar just clouds.
This effect should diminish with time as the low level boundary
layer mixes out during the day.
Short term...(today and tonight)
Issued at 320 am CST Friday Nov 27 2015
No major forecast highlights in the short term period.
Currently...upper level trough axis continues to push south now
over southern North Dakota...with strong surface high pressure
building across portions of the western and central Dakotas.
Light winds...dry air...and a mostly clear sky associated with
the surface high results in cold temperatures across western and
central North Dakota early this Friday morning...with subzero
readings west and single digits above central and east. Re-
adjusted sky cover as still seeing lake affect low stratus
streaming off of Lake Sakakawea to the southeast of The Big Lake.
Stratus has taken a more easterly trajectory last couple of hours
as surface winds become more westerly.
Return flow and warm air advection for today as surface high pressure develops
farther southeast. Best mixing and warm air advection will occur across the north
where forecast highs will approach the lower 30s. Cooler elsewhere
in the middle to upper 20s.
Warm air advection continues to spread slowly to the south after 00z this
evening. A col develops tonight over the region with a closed
upper low to our southwest...high amplitude ridge axis to our
northwest...upper level trough to the northeast...and a shortwave ridge
extending into eastern South Dakota. This pattern will maintain a
mostly clear sky and very light winds aloft.
Long term...(saturday through thursday)
issued at 256 am CST Friday Nov 27 2015
The main feature in the models continues to be the Rex block
across the western US. As the Rex block ends the upper low will
migrate north into the Central Plains Sunday night and Monday.
This will spread snow across the southern tier of counties on
Monday with accumulations possible. Current expectations are
around 3 inches across the southwest and south central by Monday
Otherwise Saturday will be mainly sunny with highs 30 to 35.
Sunday will see increasing clouds across the south and a slight
chance of snow.
Following monday's snow...which should not include much
wind...Tuesday and Wednesday will be dry with a milder trend into
the middle to upper 30s. Temperatures could be problematic across
the south...if snow accumulations occurs in the 3 inch range...
highs/lows will be affected. Did not stray too much from guidance
at this time though.
Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1203 PM CST Friday Nov 27 2015
VFR conditions are expected through the 18 UTC taf cycle with a
dry low-level southwest flow in place across the area.
short term...New Hampshire
long term...warm air advection