Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 170842

Area Forecast Discussion
National Weather Service Grand Forks ND
342 AM CDT Thu May 17 2018

.SHORT TERM...(Today and tonight)
Issued at 333 AM CDT Thu May 17 2018

Frontal boundary at 08z still moving slowly south and now just
south of Morris and Wheaton then west along the North/South Dakota
border. 850 mb winds are from the south currently and spreading
moisture in the 850-700 mb layer over the area and just enough
instability for a few showers and t-storms that are starting to
develop near Jamestown. This activity will move northeast thru the
mid morning as highlighted by the HRRR. Another small band of
showers formed in more 700/850 frontogenesis zone from south
central Manitoba into northern MN but most of this has started to
weaken since 06z. For today area will be in broad 850 mb warm
advection as frontal boundary at the sfc moves back north but it
will have hard time making it beyond I-94 in North Dakota. So for
the balance of the area elevated instability and moisture rooted
more so 850 mb region will help generate scattered showers and a
few t-storms mostly northeast/east central ND into parts of NW MN.

Late afternoon (after 21z) the front will be near Bismarck with
sfc low a bit west or southwest of BIS and enough heating is
expected to occur to allow for MU capes to reach 2-3k. Low level
shear is adequate near the sfc boundary that will be near I-94.
There is an expectation for supercell development in the
Bismarck-Dickinson area 21z-00z and the activity then spreading
and developing northeast...but intensity weakening as instability
rapidly diminishes after 00z into north central and eastern ND.

Sfc boundary will move northward partically in the RRV and WC MN
and may set up near Fargo-Bemidji later tonight. Main lift with
upper wave and 850 mb convergence favors heaviest rainfall
farther west than earlier progged with the axis of heavier
rainfall Bismarck to Devils Lake to south central Manitoba. Risk
of severe weather is low but not zero in the early evening. Window
pretty much shuts after 02z and the focus would be parts of
the far western fcst area.

.LONG TERM...(Friday through Wednesday)
Issued at 333 AM CDT Thu May 17 2018

Friday... Rain to continue on Friday as a surface low moves across
North Dakota and Minnesota. Interesting set up as rain early Friday
will be along a warm front but will transition to a cold front as
the surface low moves to the northeast. Significant rainfall
possible as there are widespread precipitable water values in the 1
to 1.3 inch range in eastern North Dakota and northwest Minnesota
based on GFS and NAM analysis. These values are above the 90
percentile for the closest sounding locations at Bismarck and
International Falls. The WPC has all of eastern North Dakota and
northwest Minnesota in a marginal risk for excessive rainfall
Friday. Dry conditions with much of the region abnormally dry will
help as the dry ground will help absorb much of this rain.

Saturday into Wednesday night... Some rain showers will persist into
Saturday but will move out to the east as the day progresses.
Highest additional accumulations will be in southeast North Dakota
and west central Minnesota. Behind the cold front high pressure
moves in bringing with it an end to the rain and cooler
temperatures. Highs on Saturday will only make it into the low to
mid 60s but a warming trend begins on Sunday with temperatures
returning to near normal. This warming continues into the work week
with temperatures rising above average by midweek. Generally dry
period under northwest flow aloft until midweek when a shortwave
trough moves in from Canada. Newer runs of model guidance still have
significant differences so impacts remain uncertain.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1156 PM CDT Wed May 16 2018

Main aviation focus is still on showers/possible thunderstorms
and eventual stratus. Best coverage still appears to be later Thu
evening, but showers (or iso thunder) could occur as early as 13Z
from the west to the east with warm front lifting north.




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