Area Forecast Discussion
Issued by NWS Bismarck, ND

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557
FXUS63 KBIS 310602
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
102 AM CDT SUN JUL 31 2016

.UPDATE...
Issued at 101 AM CDT Sun Jul 31 2016

Current convection in eastern Montana has persisted the past few
hours as the area of thunderstorms approaches western ND. Have
increased precip chances in the west accordingly, mainly using the
latest HRRR simulations. The HRRR brings the convection into the
state, then as it moves east the HRRR indicates the convection will
weaken/dissipate.

Otherwise kept the slight chance mention of thunderstorms in eastern
portions of central ND, given the established low level jet over ND
and weak upper level impulse over the James Valley.

UPDATE Issued at 913 PM CDT Sat Jul 30 2016

Earlier convection over central ND has rapidly diminished thanks
to boundary layer cooling and a related increase in MLCIN. We used
this update to reflect that trend in hourly storm chances. There`s
still a chance of renewed, elevated convection in east central ND
overnight thanks to the Theta-E advection and speed convergence in
the middle atmosphere tied to a modest 30 kt low-level jet. We did
also add a low chance of storms to northwest ND between 05 and 09
UTC in respect to the activity currently moving through northeast
MT, but again, increasing low-level stability and lack of greater
dynamic forcing suggests those storms should weaken as they move
further east. Simple extrapolation would take their remnants into
northwest ND between 05 and 06 UTC, though.

UPDATE Issued at 559 PM CDT Sat Jul 30 2016

The going forecast is on track and no significant changes were
made with this update. A few thunderstorms continue along a line
from Devils Lake to Harvey and Lemmon as of 2255 UTC. The storms
are occurring in a relatively broad axis of lower to middle 60s F
dewpoints, yielding MLCAPE of 1500 to locally 2000 J/kg. However,
deep-layer shear is weak (less than 30 kt in the 0-6-km layer) as
shown by model-derived data and the Bismarck WSR-88D VWP, which
reveals only 15 kt of mid-level flow late this afternoon. This has
and will continue to limit the risk of severe weather, with pulse-
type storms favored through the evening. We believe this activity
will diminish with the onset of nocturnal cooling, though a modest
low-level jet may induce additional convection after 06 UTC.

&&

.SHORT TERM...(This Afternoon through Monday Night)

Issued at 315 PM CDT Sat Jul 30 2016

Forecast highlights in the short term period will be chances for
thunderstorms through the period along with much warmer
temperatures Sunday and Monday. Severe storms will be possible
Sunday and Sunday night, and again Monday afternoon and evening.

Currently, a weak embedded mid level wave is interacting with
afternoon destabilization to trigger isolated convection across
central and eastern ND into southern Manitoba once again, just
west of a subtle area of surface low pressure in place over west
central ND. Lack of decent shear and mid level lapse rates should
result in mainly short-lived single cell pulse thunderstorms this
afternoon then diminishing this evening. A brief pulse to
marginal severe not out of the question however. Non-supercell
tor parameter slightly elevated again so a brief funnel not out
of the question either over my northeast.

Later tonight, models are keying in on redevelopment of
thunderstorms late evening or after midnight across either the
south central/James River Valley region, or farther south into
north central/northeastern South Dakota as a 30-40KT Low Level
Jet (LLJ) develops and noses into the aforementioned areas along
with increasing MUCAPE. Convective initialization a bit uncertain
but did increase our chances over the James River Valley region.
Any activity will likely quickly move southeast of the my
counties.

Sunday & Sunday night, not much has changed. Closed upper low
develops over central Alberta early Sunday morning, with a
shortwave ridge developing across the Dakotas. Trough of low
pressure off to our west deepens and moves into the far western
Dakotas Sunday afternoon. Resultant increasing southerly return
flow will advect additional low level moisture into our region
along with continued WAA. Surface dewpoints still appear likely
well into the 60s to low 70s ahead of the trough. Daytime highs
mid 80s east to mid/upper 90s west closer to the thermal ridge.
Plenty of instability will thus be in place at peak heating though
the better bulk shear values remain farther west until Sunday
night. Still, values of 30-35KTs expected and should be
sufficient for strong to severe thunderstorms given the MUCAPE
depicted and increasing forcing. Speaking of which, surface
trough/cold front will start to shift east into western ND mid-
late Sunday afternoon, along with increasing mid level divergence
behind the s/wv ridge and as the closed low moves farther east
transitioning our flow to more southwesterly. Capping inversion
looks to be overcome across western ND mid/late afternoon
according to latest NAM/GFS soundings. Strong to severe
convection expected to then expand east Sunday evening before
pushing out or ending overnight into Monday morning. Will
continue to mention the possible severe in the HWO.

Frontal boundary is slow to move east out of central North Dakota
Monday, so will see a lingering threat for thunderstorms
remaining across south central into eastern North Dakota. Main
threats for our area should be east by early to mid evening as the
boundary exits south and east. Plenty of shear will be available
coupled with ample MUCAPE for another threat for strong to severe
storms from southern Missouri river valley over south central ND
into the James river valley Monday afternoon and evening.

.LONG TERM...(Sunday night through Saturday)

Issued at 315 PM CDT Sat Jul 30 2016

Compact upper low digs through the Pacific Northwest on Tuesday,
then crosses the Rockies near the international border early
Wednesday before it pushes east-northeast into the plains. This will
bring shower/thunderstorm chances pushing across the area late
Tuesday...lingering into Wednesday primarily over northern/eastern
locations.

Drier conditions with seasonal temperatures expected to end the work
week as modest ridge builds over the region.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 101 AM CDT Sun Jul 31 2016

Low pressure with an associated cold front in central Montana is
forecast to move east today. The front will be the focus for
thunderstorms late Sunday afternoon and evening.

Thunderstorms are the main aviation hazard today. Early morning
cluster of storms will impact kisn-kdik between 06-09z. These
expected to generally diminish with time as they move east. A more
significant line of thunderstorms will form along the cold front
Sunday afternoon. KMOT-KBIS will see the best chance 00-06z. VFR
conditions expected outside of thunderstorms.

&&

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

$$

UPDATE...JV
SHORT TERM...NH
LONG TERM...JJS
AVIATION...WAA



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