Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 182336

Area Forecast Discussion
National Weather Service Grand Forks ND
636 PM CDT Fri May 18 2018

.SHORT TERM...(This evening through Saturday)
Issued at 317 PM CDT Fri May 18 2018

Challenge for the next 24 hours will be timing of the end of the
precipitation from west to east along with temps and winds. 500mb
wave with closed 700mb feature sitting over the western FA this
afternoon is slowly beginning to move east. As it does the
deformation zone across the Devils Lake basin will slide to the
east and continue to bring light with moderate periods of rainfall
to the northern valley. A head of this feature and the SFC low
along the MN side of the RRV a plume of 850mb moisture has brought
an area of showers to NW MN within the warm sector of the system.
As the SFC low continues to lift along the boundary extending NE
to near BDE these scattered showers will continue to lift north
across NW MN. Showers will gradually end this evening in NE ND and
by dawn in NW MN. Additional accumulations will range from a trace
in the south to up to an inch across the northern areas.

With respect to temps and winds the cold front is working through
the extreme southeastern corner of ND currently and will fill in
behind the SFC low this evening and overnight. North to northeast
winds will continue to be breezy behind the front into the late
evening diminish some overnight and ramp up again during the day
Saturday. Temps will fall quickly in the wake of the front as rain
cooled 40 degree air pushes advances east. Model guidance suggests
a clearing line in sky cover works through the area overnight with
temps falling into the 40s and even some upper 30s over the far
NW zones. Frost potential remains low there as wet soils and
mixing appear to limit radiational cooling. After the cool morning
expecting a gradual warm up into the low 60s with sunny skies.

.LONG TERM...(Saturday night through Friday)
Issued at 317 PM CDT Fri May 18 2018

Questions exist Sunday morning on frost potential. Optimal
radiational cooling from high pressure, clear skies, and calm wind
is expected over a dry, cool air mass composed of dew points within
the lower to mid 30s. This should pose the risk for frost formation.
However, recent rainfall may provide enough of surface moisture
content to favor fog formation over frost formation. This will
depend how much drying of the surface occurs Saturday within sunny
and breezy conditions. With high pressure expected to reign supreme
Sunday, the rest of the day is forecast to be dry, sunny and mild
with high temperatures getting into the 70s. High pressure slides
east Monday allowing for strengthening southerly flow and
slightly warmer temperatures.

The upper level pattern re-orients itself under split flow with the
polar jet deep into Canada and an upper level cyclone over the Great
Basin. Models continue to indicate some interaction between a
transient upper short wave trough within the base of a ridge over
central Canada and some energy emanating out of the Great Basin
cyclone. This interaction is may increase rain chances within the
Northern Plains mid next week, although guidance still struggles to
agree with best placement and timing of precipitation. Rain chances
continue to increase late next week as the Great Basin cyclone
breaks down while moving east into the Plains and another, more
potent short wave trough moves out of the Canadian Rockies into the
Canadian prairie provinces. Overnight convection may also play a
factor into Wed-Fri precipitation chances as well from greater
influence of overnight warm air/theta-e advection. Increasing
thicknesses through next week promotes a warming trend in
temperatures towards above normal, but this will be dependent of
daytime cloud cover.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 636 PM CDT Fri May 18 2018

SHowers are transitioning across the northern RRV in ND
(including KGFK and KTVF) and parts of MN near KBJI, and vis in
showers is occasionally dropping in the 3 to 6sm range (sometimes
to 2 miles briefly). IFR cigs are also spreading south and east,
and this will eventually impact all terminals this
evening/overnight before improving from the northwest to the
southeast through Saturday morning. Northeast wind gusts will
decrease later this evening (shifting more to the north in
prevailing direction), but gusty winds will redevelop by midday
Saturday on the back side of departing upper level system.




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