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Area forecast discussion 
National Weather Service Grand Forks ND
655 PM CST Friday Dec 26 2014

Update...
issued at 655 PM CST Friday Dec 26 2014

Clouds will be the main issue...as the northern valley has seen a
bit more clouds moving down out of Canada...but the west continues
to be clear. Temperatures just north of Langdon are already down around
minus 8...so think previous shifts idea of a sharp drop off and
then rising temperatures later on as more clouds come in from the west.



&&

Short term...(this evening through Saturday night)
issued at 305 PM CST Friday Dec 26 2014

High pressure will build into the region tonight. Clouds have been
slow to clear from the northwest...but the clearing continues to
make progress from west to east. Rap/hrrr guidance clears areas
along and west of the valley by this evening...but keeps areas
east of the valley cloudy through the overnight. Trended slower
with the clearing east of the valley...but still kept the idea
for clearing by morning (later updates will need to evaluate if
the hrrr/rap idea might be better). Min temperatures will be even
trickier...much dependent on cloud cover. There should be a quick
drop this evening where sky is clear...but warm air
advection/return flow kicks in after midnight which should steady
or slowly rise temperatures (at least for the dvl basin...not sure about
valley locations).

Cold front poised to drop through the forecast area Saturday night. One last
warmer day on Saturday ahead of this feature...with clouds
increasing from north to south. This frontal passage will be associated with
weak forcing...so isolated snow showers/flurries possible. Models
indicate that cold air advection will be relatively weak...leading
to a shallow mixing layer with 15-20 knots available to mix
(winds maybe breezy...but not strong).

Long term...(sunday through friday)
issued at 305 PM CST Friday Dec 26 2014

Sunday-Monday night...cold air advection regime with high
pressure building into the region. Temperatures will be much
colder than the previous couple weeks...with maximum temperatures mainly in
the single digits (above or below zero)...and min temperatures mainly
below zero. The main concern this period will be wind chill
values. The strongest area of high pressure will track across the
western Dakotas...keeping this region within a weak surface pressure
gradient. This should be enough for wind speeds at or above 5 knots Sunday
night and Monday night when temperatures will be the coldest
(leading to potential Wind Chill Advisory conditions).

Tuesday-Friday...long wave ridge forecast to remain over western
North America into Alaska while long wave trough extends from Hudson
Bay to the Desert Southwest. Long wave trough shifts over eastern
North America by the end of the period. Long wave upper ridge
deamplifies while long wave trough over Hudson Bay amplifies
through the period.

European model (ecmwf) and GFS were in good agreement at the beginning of the period.
The GFS was a little faster and becomes faster than the European model (ecmwf) for
the rest of the period. Will prefer the slower European model (ecmwf).

Will split the difference between probability of precipitation from this mornings package
and probability of precipitation for this afternoons run for Wednesday night and Thursday.

A cold day to start on Tuesday. Some moderation on Wednesday and Thu, then back
into Arctic air on Friday. High temperatures were generally increased a degree
or two for Tuesday and Wed, increased one to four degrees on Thursday and
little change on Friday.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 655 PM CST Friday Dec 26 2014

Stratus has lingered in the northern valley...and although kgfk is
clear it is right on the edge of some MVFR ceilings. Included a tempo
mention of MVFR ceilings for a few hours as some clouds could slip in
briefly before models all take the stratus eastward. Think that
kdvl...kgfk and kfar could see a period of mostly clear skies and
VFR conditions before the next round of clouds moves in from the
west after 06z. Think that kbji and ktvf will stay socked in with
MVFR ceilings through the period. Clouds moving in from the west
should put ceilings at all taf sites in the 1200-2500 range by
tomorrow night. Winds will shift around from the northwest to the
southwest but should remain below 12 kts.

&&

Fgf watches/warnings/advisories...
ND...none.
Minnesota...none.
&&

$$

Update...Jr
short term...tg
long term...tg/hoppes
aviation...Jr

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