Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 201741
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1241 PM CDT FRI MAY 20 2016

.UPDATE...
Issued at 1241 PM CDT Fri May 20 2016

Aforementioned shortwave trough continues to slide south into the
James River Valley with a scattered to broken cumulus field per
visible satellite and surface observations. Followed the
experimental HRRR ceiling forecast with increased sky cover James
River Valley and portions of north central as the altocumulus
castellanus field from the earlier update shifts north closer to
the approaching shortwave trough. Rest of forecast looks on track.

UPDATE Issued at 954 AM CDT Fri May 20 2016

The latest water vapor imagery shows a shortwave trough stretching
from the Turtle Mountains southeast into the northern James River
Valley. This is forecast to slide south during the day. Visible
imagery shows altocumulus castellanus clouds continuously reforming
over south central North Dakota. 12z BIS sounding shows the layer
of instability roughly between 750mb and 550mb. NAM BIS soundings
continue to show elevated instability into the afternoon but no
precipitation forecast, and concur with little or no reflection of
this shortwave below 700mb. Thus will likely continue to see some
clouds between 10kft and 18kft. Current forecast trends on track
at this time.

UPDATE Issued at 639 AM CDT Fri May 20 2016

Short term forecast trending well with no changes.

&&

.SHORT TERM...(Today and tonight)
Issued at 353 AM CDT Fri May 20 2016

Weak flow aloft is seen in the very short term period, but
sufficient instability beneath this weak upper low is supporting
some widely scattered thunderstorms north central early this
morning. Expect this convection to last perhaps until sunrise as
the upper low moves east after that. Friday will see a strong
upper low consolidate over the northwest CONUS with a resultant
downstream ridge over the northern plains. This pattern should
suppress convection across the region into friday night and even
most of Saturday. The NAM bufkit soundings portray a well
developed capping inversion at Dickinson and Williston Friday into
Saturday that should keep these periods dry. A persistent
southeast wind will gradually increase dew points however. High
temperatures Friday will be 70 to 80 with lows in the 50s friday
night.

.LONG TERM...(Saturday through Thursday)
Issued at 353 AM CDT Fri May 20 2016

The main concerns in this period involve the possibility of
severe weather late Saturday night, with a better chance Sunday
afternoon and night. As the northwest CONUS upper low moves east
expect to see the capping inversions erode. The most unstable
cape becomes focused across eastern Montana into into western
North Dakota Saturday evening. However better shear remains west.
So the threat of severe weather should hold off until after
midnight and this just expected to be a marginal threat over the
western third of the state late. On Sunday, much better 0-6 km
shear makes it`s way into western and central North Dakota with
the best cape focused in cental North dakota Sunday afternoon
evening. At this time expect a slight risk for large hail and
damaging winds over mainly central North Dakota.

By Monday the cold front has pushed through and have taken this
opportunity to remove the threat of thunderstorms. Just went
showers. the Tuesday through Thursday period will have southwest
flow aloft, a steady stream of short wave energy that will support
scattered to isolated thunderstorms each day. Also expect a slow
warming trend from the 60s and lower 70s Monday and Tuesday into
the 70s Wedneday and Thursday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1241 PM CDT Fri May 20 2016

VFR conditions are forecast to prevail across western and central ND
this afternoon through Saturday morning. There is a chance of MVFR
ceilings (stratus/low clouds) developing by Saturday morning, but we
were not confident enough in its formation to include in the 18 UTC
TAF release. Otherwise, east-southeast winds gusting to around 25 kt
are expected this afternoon and again on Saturday. There may be low-
level wind shear in some locations tonight, depending on how much
surface wind speeds diminish at any given terminal.

&&

.BIS Watches/Warnings/Advisories...
NONE.
&&

$$

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



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