Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 281752
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1252 PM CDT SAT MAY 28 2016

.UPDATE...
Issued at 1252 PM CDT Sat May 28 2016

Current forecast for precip chances looks on track. Noted convection
beginning in southwestern North Dakota from a Beach to
Marmarth/Bowman line as per the short term high res models. Current
surface based CAPE indicates CAPE values from 500-1000 J/Kg over
southern and eastern North Dakota...with low clouds in the northern
areas of the state inhibiting surface heating. Wind shear remains
weak with marginal mid level lapse rates. Thinking has not changed
regarding sub-severe nature of expected convection...but potential
remains for some stronger updrafts that might produce some small
hail that might reach the ground.

Regarding temperatures...temps a bit slower to rise in the north
beneath the low clouds than we had forecast, but not by much. Mainly
blended current temps with afternoon forecast using a blend of high
res models.

UPDATE Issued at 947 AM CDT Sat May 28 2016

We made some minor adjustments to PoPs through the late morning to
reflect the ongoing generally dry conditions. We still expect that
to change by afternoon, when shower and thunderstorm activity will
increase. Forecast soundings, including from the most recent RAP,
support up to 500 J/kg of MLCAPE developing over western ND ahead
of the shortwave trough moving through eastern MT this morning. We
expect a line of showers and thunderstorms to develop as that wave
moves eastward, likely reaching the Highway 83 corridor by 23-01
UTC per recent convection-allowing model guidance. Deep-layer
shear will be weak, so we expect storms to be sub-severe, but cold
air aloft with 500 MB temperatures near -16 C suggests stronger
updrafts could produce small hail.

UPDATE Issued at 642 AM CDT Sat May 28 2016

The 06-10 UTC high resolution suites are well in support of the
previous forecast for today highlighted by morning fog and
followed by afternoon and evening thunderstorms, especially
across the west. The forecast was blended to observed trends
through 11 UTC.

&&

.SHORT TERM...(Today and tonight)
Issued at 238 AM CDT Sat May 28 2016

Stratus across the north and into portions of central North Dakota
this morning, followed by showers and thunderstorms developing
west in the afternoon moving into central ND late afternoon into
the evening highlight the short term period.

The latest fog/stratus loop and surface observations show a wide
swath of stratus north through portions of central North Dakota
early this morning. Where the stratus has lowered enough to reach
ground level, patchy fog is being reported with visibilities
mainly between 3 and 6 miles. Have followed the HRRR and RAP13
for initialization and sky forecast. Low level northeast winds
continue to advect in the lower clouds from southern Canada. A
good proxy for the southern most extent should be near and along a
line from Dickinson into Bismarck and Jamestown. These clouds will
slowly lift through the morning with an overall mostly cloudy sky
dominating.

The water vapor imagery shows our next pair of shortwaves, one
located near Phillips, Montana, and the second scooting through
the Idaho panhandle. These shortwaves and an associated surface
cold front will be the catalyst for shower and thunderstorm
initiation in the west between 18z and 21z today, then shifting
toward central North Dakota between 00z and 06z Sunday. Most
unstable cape across the west this afternoon on the order of
between 500 and 1000 j/kg, and 0-6km bulk shear remains weak
between 20 and 25kt. Cape quickly fades between 03z and 06z as the
precipiation shifts into central North Dakota.

The far southern James River Valley will get clipped by a few
showers or thunderstorms through the morning, which are emanating
around an upper low in northeast Nebraska. Current local and
regional radar shows isolated showers in LaMoure and Dickey
counties.

.LONG TERM...(Sunday through Friday)
Issued at 238 AM CDT Sat May 28 2016

Main highlight is the severe thunderstorm potential Monday, mainly
over far southwest into portions of south central North Dakota.
SPC continues to advertise a slight risk in this area.

Preceding the potential severe weather will be a dry and pleasant
Sunday with highs in the 70s. A mid level transitory ridge slides
across western and central North Dakota and will keep the area dry
until 00z Monday. Instability increases Sunday night with a chance
of showers and thunderstorms possibly developing on the heels of a
weak to moderate low level southerly jet in southwest and into
south central North Dakota.

Then, a potent closed upper low which is currently over western
British Columbia, advances into northeast Montana Monday
afternoon. A leading shortwave is forecast to produce showers and
thunderstorms Monday afternoon through Monday night. Model
continuity in advertising a high cape and shear environment
results in higher confidence for severe weather.

With the slow movement of the upper low into western North Dakota
Tuesday, another round of showers and thunderstorms, possibly
severe appear to gain momentum again across southern North Dakota.
The upper low finally gets pushed into the southern James River
Valley Tuesday night with drier air nudging from west to east.

Wednesday afternoon through Friday will be under a drier northwest
flow. It is possible that a couple shortwaves embedded within the
flow could create the potential for some showers, but at this
point, areal coverage for any measurable precipitation is scarce.
It looks dry with a warming trend into Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1252 PM CDT Sat May 28 2016

MVFR ceilings will linger into mid/late afternoon for KISN, KJMS and
KMOT. Showers and thunderstorms have begun to develop in western
areas, continued development is expected in western and central
areas through the afternoon. Thunderstorms will likely impact each
of the TAF sites. Gusty winds, reduced visibilities, and lower VFR
ceilings are anticipated as showers and thunderstorms move through
the TAF location.

&&

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

$$

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


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