Scientific Forecaster Discussion
fxus63 kfgf 151557
Area forecast discussion
National Weather Service Grand Forks ND
957 am CST Fri Nov 15 2019
issued at 956 am CST Fri Nov 15 2019
Highly variable conditions across the forecast area this morning. Some
clearing occurred overnight across northwest Minnesota, where
lows dipped to around zero. Now these areas are seeing sunshine
with temperatures back into the mid 20s. Further west, clouds
cover a good part of eastern North Dakota. Fog formed overnight
over portions of central and western North Dakota, and did brush
the Devils Lake to Valley City corridor. Some fog is lingering yet
in these areas, so did extend the mention of fog until around
noon. Otherwise expect winds to turn a little more southerly late
today into tonight.
Update issued at 735 am CST Fri Nov 15 2019
Axis of dense fog is remaining just west of our County Warning Area line, and so
far no reports of freezing drizzle near our County Warning Area (though we can't
rule it out through 15z). Clear area in Minnesota lingering, but mid-high
clouds should eventually overspread this. Still expect low clouds
to lingering from Red River west today liming how warm we get.
Adjustment made to reflect near term temp/sky trends otherwise no
changes necessary at this time.
Short term...(today through Saturday evening)
issued at 409 am CST Fri Nov 15 2019
This morning: moisture pooling along stalled frontal zone
extending from southeast ND to northwest ND allowing for fog
development, and few reports of dense fog along our far western
County Warning Area. Rap soundings still show potential for deepening of saturated
layer that with any smaller scale forcing could support freezing
drizzle development. This his highly uncertain though, as so far
depth of saturation layer not as deep and any indication of
forcing from the Escarpment west of the Red River isn't there. Will
monitor trends on any dense fog or freezing drizzle potential, but
so far keeping mention confined to severe weather potential statement only.
Today: low confidence in position of frontal zone as it may remain
stalled over our western County Warning Area through the day, and this could keep
stratus in place within slow temp recovery today. Models still
show a saturated layer, but again besides maying stratus or
lingering fog (better fog potential along our west) if we do not
see drizzle this morning, then it's hard to have confidence
during periods when saturated layer is even shallower.
Tonight-saturday: warm air advection off the surface increases with south-
southeast flow ahead of next approaching shortwave trough. This
will allow for deepening of moisture in the lower levels once
again and high res guidance is showing light/spotty signal likely
associated with potential drizzle development. As with this
morning, depth of saturation and forcing within this layer are
uncertainty, but potential is there and I went ahead and added
slight chance dz/fzdz mention late tonight and Saturday morning.
Forcing/moisture advection increases Saturday afternoon, which is
when models show increasing measurable precip signal. This also
happens to be when temperatures should be above freezing (mid 30s
to near 40), favoring drizzle or rain through the majority of the
Initially a dry layer ahead of the main push of forcing/moisture
advection will limit ice introduction aloft, so while temperatures
fall late afternoon as front approaches. This could result in a
messy transition of precip type along the leading edge of the main
period of precipitation until saturation to tw occurs later
Saturday evening when snow would then be favored. It's hard to
have a lot of confidence due to timing of cold air (could be too
warm at surface at onset), but we will need to monitor these
periods to see if there are any potential impacts.
Long term...(saturday night through thursday)
issued at 403 am CST Fri Nov 15 2019
After dry layer aloft saturates expect mainly light snow as precip
type through Sun morning. Any snowfall would be light, and less
than 1 inch.
Another round of light snow moves in from the west Sun night.
Another dry layer moistens and may produce a brief period of
freezing rain/drizzle over the far western zones Sun night and Mon
morning. Otherwise very light rain or snow elsewhere Sun night
through Mon night.
Mon - Thu
Long wave pattern becomes more split and lower in amplitude. Long
wave ridge essentially remains over western Canada. Long wave trough
expands over the southwest US and long wave trough over eastern
Canada/Great Lakes shift farther north.
Operational GFS become a faster solution than the European model (ecmwf) after Tue.
Cutoff low forms in the Desert Southwest and a progressive pattern
occurs across the northern states by Wed.
Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 540 am CST Fri Nov 15 2019
LIFR ceilings over central ND extend east impacting kdvl. Further
east MVFR ceilings are prevailing over kgfk, kfar, and ktvf, with
VFR over bji in northwest Minnesota. Where lower ceilings are currently
reported they will be slow to improve, however a period of VFR is
expected at most terminals (except dvl) by this evening before
stratus spreads eastward once again late tonight. Kbji should
remain VFR thorugh the taf period, though there is an outside shot
of stratus spreading further east than currently depicted
(especially late tonight.
Fog has development around dvl, with patchy dense fog (vlifr)
over parts of central ND further away from the terminal. Trend
should be toward vis improving through 15z, though some vis
restrictions may remain possible. Better chance for fog
redevelopment late tonight at kdvl and this fog may extend far
enough east to start to impact kgfk/kfar (still uncertain for
those terminals). This morning, we can't rule out light fzdz at
kdvl, however trends aren't indicating this and as fog/better
moisture moves west this morning this threat should end (by 15z).
There may be another window for freezing drizzle after 09z-15z
Saturday, however probability/coverage too low to include in tafs.