Area Forecast Discussion
Issued by NWS Grand Forks, ND

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KFGF 070312

Area Forecast Discussion
National Weather Service Grand Forks ND
1012 PM CDT Sat Jun 6 2020

Issued at 1008 PM CDT Sat Jun 6 2020

Showers continue over far NE ND and thru much of nrn MN in broad
area of 700 mb warm/moist advection. No thunder noted.

Attention turns to line of storms with a long history of winds
over 60 mph that moved thru parts of Wyoming and Colorado earlier
and now moving north-northeast 60 mph thru NW SD into SW ND.
Severe t-storm watch for far western fcst area, but as discussed
with SPC uncertainity in regards to how long the high wind
potential will last as it will outrun the 50-60 kt 850 mb jet
which...and instability will become increasingly elevated. HRRR
past couple runs have area of t-storms increasing in width and
less of a line as it moves into central ND past Bismarck and
therefore less wind threat.


.SHORT TERM...(This evening through Sunday night)
Issued at 221 PM CDT Sat Jun 6 2020

This afternoon and evening... A line of rain showers continues to
moves across eastern North Dakota and northwest Minnesota this
afternoon. There is very little instability in the environment
the lines is moving into so thunderstorms are not expected. There
could however still be an isolated thunderstorm farther south in
the Red River Valley where the atmosphere is more unstable.

Saturday night into Sunday morning... Later tonight additional
thunderstorm development is expected as a shortwave moves into the
Northern Plains. A strong LLJ combined with high precipitable
water ranging from 1 to 1.5 inches will provide an environment
favorable from rain. When combined with MU CAPE values between
1500 and 2500 J/kg and bulk shear values around 50 knots some
strong to severe thunderstorms are also expected. While the best
chances for significant severe convection remains to the south and
west in western ND and SD some of these storms could continue
into eastern North Dakota and northwest Minnesota overnight. If
these storms do make it this far north and east they will likley
be in some form of linear system or MCS with wind as the main
threat. With the high precipitable water heavy rain will also be a
threat, but with dry soils the main flooding threat would be in
urban areas.

Sunday afternoon into Sunday night... An hot an moist environment
will be present with temperatures in the upper 80s and low 90s
combined with precipitable water values in the 1 to 1.5 inch
range. These precipitable water values are between the 90th
percentile and max in NAEFS R-Climate so this is a very moist
environment for this time of year in the Northern Plains. Hot and
moist conditions lead to high instability and CAPE with MU CAPE in
some CAMs reaching well into the 4000 to 5500 J/kg range. This
unstable environment combined with an approaching warm front and
bulk shear of 40 to 60 knots creates an environment favorable for
all modes of severe weather. The high CAPE environment helps lead
to high hail index values suggest large hail will be possible.
With surface to 1 km SRH also high in the 200 to 300 m2/s2 range
and generally low LCLs tornadoes will be possible. Also with the
environment favorable for supercells very high winds will also be
a threat. There have been some variations between different
ensemble systems and CAMs to there remains some doubt as to where
the greatest chances will occur in our region. There is enough
confidence however to state the thunderstorms, likely severe, will
be present on Sunday and into Sunday night.

.LONG TERM...(Monday through Saturday)
Issued at 221 PM CDT Sat Jun 6 2020

Monday-Saturday...Model guidance in decent agreement with the
overall pattern, with southwest flow aloft gradually transitioning
to northwest flow aloft and then ridging toward the weekend. Active
weather to start the period will become much quieter (drier) by mid-
week into the weekend. Temperatures will also be much cooler.  With
that all said, the most uncertainty exists at the beginning half of
the period as the track of the tropical depression will dominate
what happens across this region. The main impacts will be severe
thunderstorm potential Monday afternoon, and then heavy
rain/excessive rainfall potential into Tuesday. The 12z ECMWF tracks
the tropical depression further west (and brings more rainfall
further west) compared to other guidance. Although this is still an
outlier scenario, it indicates the uncertainty that still exists. At
any rate, a strong baroclinic zone with a cold front pushing
eastward will bring severe thunderstorm chances Monday evening
(where the front is set up), and then a prolonged period of moderate
precipitation into Tuesday (with the area and duration of the
moderate precipitation dependent on the track of the tropical
depression). Excessive rainfall potential will also be dependent on
what happens before Monday (if heavy rainfall saturates the soils).


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 713 PM CDT Sat Jun 6 2020

A series of convective rain bands will work across the FA from
southwest to northeast during the early evening... in advance of
stronger convection expected during the overnight period. Generally
VFR conditions are expected outside of showers this evening, with
southeast surface winds gusting from 15 to 30 kts. During the
overnight period and into early Sunday morning expect more
widespread showers and thunderstorms with areas of MVFR conditions
in heavy rain and strong gusty winds. This should lift through
eastern ND from 06z through 10z, and through northwest and west
central MN from 09z through 15z.

Additional strong to severe thunderstorms are possible again late
Sunday afternoon into the early evening.



AVIATION...Gust is the U.S. government's official web portal to all federal, state and local government web resources and services.