Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 220303

Area Forecast Discussion
National Weather Service Bismarck ND
1003 PM CDT SAT MAY 21 2016

Issued at 1003 PM CDT Sat May 21 2016

Based on LAMP guidance, BUFKIT, and observations, the wind
advisory for the southwest was extended to midnight MDT.

Slight adjustments were made to POPs to reflect the latest radar
trends. Otherwise, the forecast is on track.

UPDATE Issued at 652 PM CDT Sat May 21 2016

No significant changes were needed with this update. As of 23 UTC,
stout south-southeast winds continue across the area, partially as
a response to noteworthy surface pressure falls near 3 MB/3 HR in
northeastern MT. The wind advisory is on track. A few sites to the
north and east of the headline have touched advisory criteria over
the last few hours, but not consistently, and peak gusts have been
generally below 45 mph outside of where we have the advisory in
southwestern ND. Thus, we did not expand it at this time. We are
watching the developing line of storms from eastern MT southward
into northeast WY at this hour, but their propagation has a more
northerly than easterly component thus far. Moreover, SPC meso-
scale analysis output and various model-based forecast soundings
suggest strong mid-level capping is in place over western ND and
may continue to exert its influence into the night, calling into
question the potential strength of storms once they enter ND. We
will continually re-evaluate through the evening, though.


.SHORT TERM...(This evening through Sunday night)
Issued at 126 PM CDT Sat May 21 2016

Severe weather potential for portions of western and central
North Dakota highlights the weather through Sunday night.

For the near term, through early this evening, the wind advisory
in the southwest remains in good standing. Will let this continue
and let the next shift take control.

Soundings indicate strong CIN/capping layer west and central this
evening with a slow erosion overnight in the far west. However,
not enough erosion at this point for much more than a few strong
to possibly severe thunderstorms overnight. Showers and thunderstorms
in eastern Montana will limp into the west toward 06z Sunday, then
shift from west to east Sunday morning. The main severe hazards
continue to be wind and hail.

Strong warm air advection via southeasterly flow will higher
dewpoints and low clouds currently upstream into south central ND
overnight and through most of Sunday. Timing on when the low clouds
begin to erode will be the key for surface based convection
Sunday. Indications from the experimental HRRR ceiling forecast
show the area of low clouds from Minot to Bismarck and into
Jamestown will erode between 20z and 00z. Minot would be the
first to see the erosion followed by Bismarck and Jamestown.

After talking to SPC, and given the full expectation that overcast
conditions will be the rule until mid afternoon Sunday in most of
central ND, the consensus is that there will be an area of
thunderstorms developing from Lemmon SD to Dickinson, and
narrowing northeast into Minot between 21z Sunday and 00Z Monday.
The NAM seems to fit this conceptual model nearly perfectly. The
NAM shows convection initiation will be right along the front,
but west of the stratus or low cloud deck. Thereafter, some
unknowns appear. How much erosion of the low clouds and enough
surface heating will be obtained prior to the convection and
surface cold front approaching from the west. The maximum CAPE and
850mb THETA-E axis slightly outrun the surface cold front,
highest shear, and strongest ascent. Nonetheless, the Bismarck
NSharp sounding indicates that Precipitable Water rises to 1.30
inches with a K-index of 41, which is indicative of some heavy
rain along with a hail and wind threat between 00z and 03z Monday
across central ND.

The cold front and precipitation shield slide into the southern
James River Valley 06z-12z Monday as increasing stability shifts
from west to east behind the front.

.LONG TERM...(Monday through Saturday)
Issued at 126 PM CDT Sat May 21 2016

Upper low remains over Saskatchewan on Tuesday before slowly
meandering east through mid-week, though models are differing on
whether to keep it closed or start opening it up. Either way, this
will keep cyclonic flow over the area bringing a near daily
chance for showers/thunderstorms. Temperatures will start out
above average, cooling to near average as the low pushes eastward.

Low chances for showers/thunderstorms will remain in the forecast
into the end of the week along with near normal temperatures as a
generally unsettled pattern sets up in the wake of the departing low
with the next upper low lifting from the desert southwest into the
plains. Still some question on the exact placement on this system.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 652 PM CDT Sat May 21 2016

MVFR and IFR ceilings in low clouds (stratus) will likely develop
over southwest and central ND tonight, and linger through midday
Sunday, before finally lifting Sunday afternoon. The KDIK, KBIS,
and KMOT terminals will be most impacted by the low clouds. A few
showers and storms will likely move across western ND tonight and
into central ND late tonight and Sunday morning. Finally, stronger
storms are likely in parts of western and central ND after 21 UTC
Sunday, and continuing through Sunday evening.


.BIS Watches/Warnings/Advisories...
Wind Advisory until midnight MDT tonight for NDZ031>033-040-041-



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