Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 281300
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
700 AM CST Mon Nov 28 2016

.UPDATE...
Issued at 655 AM CST Mon Nov 28 2016

Main change for the early morning update will focus on POPs.
Current HRRRTL guidance is doing a decent job handling breaks in
the bands of precipitation rotating around the main vort over west
central MN. Will blend in the latest HRRRTL through 17Z. Current
top down grids generating a very reasonable solution for rain-snow
transition, with 13Z forecast verifying for snow at Carrington and
Devils Lake and rain at Cooperstown. Will make no changes and
expect diurnal warm up and a slightly deepening (50 mb off latest
sounding) near surface warm layer to help transition rain/snow to
rain further west of current line over next several hours.

&&

.SHORT TERM...(Today and tonight)
Issued at 326 AM CST Mon Nov 28 2016

The forecast challenge for the short term focuses on the evolving
system that is generating a rain/snow is west of the
valley...turning to all snow around the Devils Lake area. The
current p-type grid is doing an excellent job verifying with web
cams at Binford (snow)...Emerado (snow) and Pembina. In general,
the current rain to snow transition line is along a Wimbledon to
Finley to Northwood to Gilby to Hoople to Roland line...with all
snow by around 10 miles west of the line. Along Highway 2, the
transition appears to be vicinity of Grand Forks AFB exit however
accumulation is not impressive until the Devils Lake region.

Current METARs indicate the surface low between Watertown and
Huron SD with water vapor imagery indicating upper vort centered
between Watertown and Marshall SD. The first wave of precipitation
is now seeing dry weather in the southeastern zones (west central
MN) with more showers over the Cities area moving NW and should
fill in the dry area by mid day. One challenge in regards to POPs
will be timing individuals waves and in general addressing these
breaks with chance POPs versus timing in breaks. The surface low
will gradually lift over Richland County ND before it settles
there and wobbles over the area through Tuesday morning.

Warm advection and diurnal temperature increases should help push
the rain snow transition line back into the Devils Lake
area...with the far western portion of Benson County remaining
snow...and sliding back to the east as the column cools further
west and surface temperatures cool overnight due to a very shallow
warm layer that is melting snow into rain along the current
transition line. More solid snow may push east from the James
Valley into the Valley City area by Tuesday morning, however the
late start for constant snow will keep snowfall accumulations
minimal in the far southwestern zones.

The current headlines look reasonable despite rain heading into
Cavalier county as opposed to snow. Surface temperatures are
around 32 F across Cavalier...Ramsey and Towner counties (some
scattered warmer temps around 34 F), so the northern portion of
the advisory has the best risk for some freezing rain with some
light ice accumulations on untreated surfaces. The highest
snowfall impacts continue to be in far western Benson and Towner
counties, with western Benson seeing 3 to 5 inches by midnight
very possible, and rapidly increasing amounts by the time you get
to Rugby.

.LONG TERM...(Tuesday through Sunday)
Issued at 326 AM CST Mon Nov 28 2016

The low begins to eject out into the arrowhead on Tuesday morning,
pulling the deformation zone further into the western counties of
our CWA and pulling snow further to the east on Tuesday. The
majority of the area however continues to look like rain until
Tuesday night. Decreasing overnight lows and colder air being
pulled into the back of the low will cause a gradual changeover
from rain to snow overnight Tuesday...and expecting to be snow
across the entire area by Wednesday morning. The deformation zone
will remain over eastern ND and highest QPFs should remain west of
the valley for Tuesday night into Wednesday...leading to keeping
POPs in the west categorical from 12Z Tuesday through 18Z
Wednesday (about 25% higher than SuperBlend guidance). This
forcing should gradual weaken Wednesday afternoon and will begin
decreasing POPs after 18Z Wed. Light snow will continue on into
Thursday morning with little additional accumulation (less than an
inch).

Thursday through Sunday...

Long wave trough over MN moves to eastern Canada by the end of the
period. A low amplitude long wave trough becomes established over
the Northern Plains by Sun.

Upper level waves rotating around upper low will continue for Thu
and Thu night and produce periods of light precip. The GFS was a
faster solution than the ECMWF. Little confidence for this forecast.

The GFS and ECMWF are out of phase over the Northern plains for much
of the period. The ECMWF wants to move upper low over southwest US
into the central plains by Sun while the GFS leaves the upper low
cut off over the southwest US.

High temperatures were decreased a degree or two for Thu and Fri and
increased a degree or two for Sat. Little change to temps for Sun.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 655 AM CST Mon Nov 28 2016

IFR conditions now at all sites with some breaks into MVFR cigs as
bands move out of area (currently FAR)...should be short lived
breaks and predominantly IFR through the next 24 hours.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until 10 AM CST this morning for NDZ006-
     007-014-015-024-026-054.

MN...None.
&&

$$

UPDATE...Speicher
SHORT TERM...Speicher
LONG TERM...Hoppes/Speicher
AVIATION...Speicher



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