Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 311807
AFDBIS

AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
107 PM CDT TUE MAY 31 2016

.UPDATE...
Issued at 107 PM CDT Tue May 31 2016

We increased forecast wind speeds and issued a wind advisory for
western ND with this update. Gusts to 50 mph are being observed in
northwest ND as of midday, and are forecast to spread southward
into southwest ND this afternoon per the LAMP guidance we used to
adjust forecast winds through 00 UTC. That is in line with modest,
2-3 MB/3 hour pressure rises observed in northeast MT as of 18 UTC
and which are forecast to push into western ND this afternoon. The
forecast soundings at Williston and Dickinson from the HRRR reveal
50 kt winds in the mixed layer, further supporting strong gusts.
Low-level subsidence and momentum transfer will not be especially
strong, so we don`t expect all of that wind to reach the surface,
but shower activity will likely contribute to a somewhat erratic
nature to peak gusts as it helps mix down some of those stronger
winds aloft toward the ground, too.

UPDATE Issued at 948 AM CDT Tue May 31 2016

Overall the going forecast is on track and was merely blended with
recent observations and high-resolution model guidance. Showers in
north central and northwest ND are still forecast to wrap south-
ward into western and parts of south central ND this afternoon as
the mid- and upper-level low over central ND slowly shifts to the
northeast. As mentioned in the previous discussions, there should
be enough instability for weak thunderstorms this afternoon.

UPDATE Issued at 641 AM CDT Tue May 31 2016

Surface low pressure over eastern ND and mid to upper level low
tracking from southwest into south central ND this morning. This
is producing a widespread area of showers across northwest and
especially north central ND and into southern Canada. As the upper
low tracks slowly east today, wrap around moisture will spread
south into southwest and south central ND. Forecast sounding
indicate some weak instability this afternoon so kept the mention
of thunder in for this afternoon. However, we did drop the mention
of thunder this morning.

&&

.SHORT TERM...(Today and tonight)
Issued at 312 AM CDT Tue May 31 2016

Rainshowers with embedded non-severe thunderstorms along with
much cooler temperatures highlights the short term period.

The latest water vapor imagery shows a closed upper low circulating
over Jordan, Montana. A leading mid level shortwave was approaching
the Turtle Mountains, with its circulation and widespread rain
shower signature evident on local radar. This will morph with the
closed 500-300mb low as it slides into western and north central
North Dakota today, shifting into eastern North Dakota and western
Minnesota tonight. In doing so, steady rainshowers with embedded
thunderstorms will continue north, with the precipitation shield
filling in from west to east through the day. Bufkit soundings
show that the LFC, level of free convection, at around 1500ft
above ground level today with a weak cape signature of a couple
hundred joules/. 0-6km bulk shear of 20kt to 30kt and 850mb to
700mb lapse rates around 6.5c/km. Parameters weak, but enough to
warrant isolated on severe thunderstorms embedded within the
widespread rain showers. Much cooler with highs in the mid 50s
west to mid 60s James River Valley.

.LONG TERM...(Wednesday through Monday)
Issued at 312 AM CDT Tue May 31 2016

A dry period is forecast Wednesday through most of Thursday as a
broad mid level ridge transitions from the northern Rockies into
North Dakota. This will be followed up by a two shortwave troughs,
one Thursday night and the second one Friday. For Thursday
evening/night, a modest low level 850mb southerly wind of 20-25kt
will transport moisture/instability north, along and ahead of a
weak cold front which will push from west to east overnight.
Expect a chance of elevated thunderstorms with cape between 500
and 1000 J/kg and 0-6km bulk shear of 30kt-40kt. Showalter indices
of -2c to -4c will slide from west to east along the periphery of
the low level instability axis. The chance for showers and
thunderstorms will continue with the second shortwave Friday. The
highest chances will be from the Turtle Mountains south into the
James River Valley. Most of the west looks removed from any
precipitation at this time.

Saturday through Monday look dry along with a moderating trend as
an upper level ridge builds over the northern Rockies. Afternoon
highs will rise from the upper 70s into the lower 80s through the
period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 107 PM CDT Tue May 31 2016

Conditions will vary between VFR and MVFR at KBIS/KISN/KDIK/KJMS,
as showers linger across western and central areas through much of
the TAF period. Guidance is suggesting prevailing IFR ceilings at
KMOT for several hours starting around 22Z. Chances for
thunderstorms will increase through the afternoon, with chances for
showers tapering off, from west to east, through the overnight
hours.

Northwesterly winds will be gusty through the afternoon, with the
strongest winds expected in KISN/KDIK.

&&

.BIS Watches/Warnings/Advisories...
Wind Advisory until 7 PM CDT /6 PM MDT/ this evening for NDZ001-
009-017-018-031>033-040-041-043-044.

&&

$$

UPDATE...CJS
SHORT TERM...KS
LONG TERM...KS
AVIATION...AC


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