Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 020007
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
707 PM CDT Mon Jun 1 2020

.UPDATE...

Issued at 659 PM CDT Mon Jun 1 2020

Area of SCT-OVC mid/upper level clouds will move from west to east
across western and central ND this evening, and have updated sky
cover grids accordingly, using a blend of the HRRR and NBM.

Will maintain overnight convection as inherited (see discussion
below), but did make some minor tweaks based on latest high res
guidance. Uncertainty remains on the high side.

One of the more noticeable edits made for this forecast issuance
was to winds 09Z early Tue morning into the day Tuesday (later
half of the aviation period). Models in decent agreement with a
frontal boundary moving southeast through the area associated with
the mid level wave bringing the chance for showers/storms
overnight-Tuesday AM. Increased winds out of the northwest behind
the FROPA based on last few high res model runs and utilizing
BUFKIT soundings.


&&

.SHORT TERM...(This evening through Tuesday)
Issued at 243 PM CDT Mon Jun 1 2020

The main concern for the short term period is the development of
showers and thunderstorms over western North Dakota late tonight,
shifting into central North Dakota Tuesday morning. There is a
conditional threat for severe hail from southwest into far south
central North Dakota.

Quiet weather this afternoon with deep layer subsidence over the
Northern Plains, although a bit breezy near the Canadian border in
response to a surface low moving into central Manitoba. Shortwave
energy is forecast to approach western North Dakota late tonight.
Sufficient forcing in the form of mid level height falls and low
level frontogenesis appears to be in place for the development of
showers and thunderstorms after sunset over eastern Montana/western
North Dakota. Thunderstorms are not expected across the northern
third of the state due to weaker mid level lapse rates and little,
if any, MUCAPE.

Farther south, there is model consensus that a pool of MUCAPE
exceeding 1000 J/kg will protrude into southwest North Dakota late
tonight. If this instability gradient is able to intercept rising
air parcels from the aforementioned forcing mechanisms, allowing for
deep moist convection, a large hail threat would likely develop
given the presence of at least 40 kts of effective bulk shear.

There are variations among guidance on both the northward extent and
degree of instability. An examination of model soundings seems to
indicate that this uncertainty is being driven by the amount of
relative humidity above the boundary layer. The NAM has been the
most aggressive in advecting sufficient moisture to both increase
CAPE and decrease CIN. An example 12Z initialized NAM sounding from
Bowman valid at 09Z tonight shows 1735 J/kg CAPE and no convective
inhibition near 700 mb (along with 52 kts of 2-6 km shear!).
However, all deterministic models are at least hinting at moisture
transport and theta-e advection being present at 700 mb, which gives
us caution in not trying to downplay this threat too much, despite a
lack of support from CAM reflectivity and UH fields.

If a severe threat does develop, it may shift into south central
North Dakota early Tuesday morning, with the only deterring factor
being a weakening of mid level moisture transport and theta-e
advection. Otherwise, expect scattered showers (north) and
thunderstorms (south) to continue across central North Dakota
Tuesday morning as the mid level shortwave propagates eastward, with
forcing possibly being aided by the right entrance region of an
upper level jet in southern North Dakota.

While most of the area will experience dry weather Tuesday
afternoon, there is potential for additional thunderstorm
development across north central North Dakota Tuesday afternoon, but
overall forcing looks weak. Any storm that develops would encounter
a low CAPE/high shear environment.

.LONG TERM...(Tuesday night through Monday)
Issued at 243 PM CDT Mon Jun 1 2020

A quasi-zonal flow pattern is forecast for mid week, with near to
slightly above normal temperatures. A mid level shortwave with an
attendant surface boundary is forecast to move across the state on
Wednesday. Scattered thunderstorms may develop from southwest into
central North Dakota Wednesday afternoon and evening. Modest
buoyancy and increasing deep layer shear may support a severe
threat. A discrete storm mode is favored, with shear vectors
oriented perpendicular to the boundary. There may be other pieces of
energy that pass through the zonal flow through Thursday, but
predictability is lower.

Upper level ridging will quickly amplify over the Northern Plains on
Friday as longwave troughing digs over the western CONUS. There is
general model consensus that a potent shortwave will approach the
region in southwest flow aloft on Saturday. The GFS continues to be
more progressive with this wave than the ECMWF, which delays any
precipitation in North Dakota until Saturday night. Nevertheless,
chances for showers and thunderstorms will be increasing on
Saturday. Anomalously high precipitable water and deep warm cloud
layer depths may support a heavy rain threat on Saturday. A severe
threat cannot be ruled out, but this looks more uncertain.

Additional pieces of energy are forecast to pass through the region
in southwest flow aloft Sunday into early next week. Given the time
of year and forecast instability and shear, strong to severe storms
cannot be ruled out, though details remain very far from certain.
Temperatures should continue to trend near to above normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)

Issued at 659 PM CDT Mon Jun 1 2020

VFR flight conditions through the 00Z period. There will be a
chance for showers and thunderstorms after 06Z starting in
western ND, then shifting into central ND through Tuesday morning.
The better chances for thunderstorms remain at KBIS and KDIK.
MVFR to IFR visibility will be possible with a storm, but ceilings
should remain VFR. High uncertainty on shower and thunderstorm
potential, and will fine tune TAFs as certainty increases and/or
when storms start developing into the area.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...NH
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...NH



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