Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 270947
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
447 AM CDT Thu Jun 27 2019

.SHORT TERM...(Today and tonight)
Issued at 332 AM CDT Thu Jun 27 2019

Thunderstorms highlight the short term period.

Ongoing convection continues to lift northward into south central
ND this morning. We did issue one warning earlier on what looked
to be a bookend vorice and bowing segment northward from SD into
Adams, Grant and Sioux counties. Then we started getting strong
winds gusts south of the main line of convection, in SD. After
coord with ABR, we issued a short High Wind Warning to cover these
wake low winds over Grant and Sioux counties, that are not
associated with the line of convection but are convectively
induced.

The leading edge of convection will move through far south central
and the southern James River Valley early this morning. Although
the threat of a local severe gust remains, think for the most part
convection will remain below severe levels as we are heading
toward the wee hours of the night.

Once the early morning convection ends, models are in pretty good
agreement in keeping it dry through the day. There is some
indication of lingering convection currently over northeast
Montana, festering over far northeast Montana into northwest ND
through the morning. But for the most part, expect dry conditions
with building upper heights over the region ahead of the upper low
over the Pacific Northwest.

Afternoon and/or evening convection today over north central and
northeast Montana moves into northwest North Dakota late tonight.
Latest SPC outlook has a slight risk for severe weather over a
good portion of western ND, and an enhanced risk over northeast
Montana. Based on deterministic and numerous CAMS, will hold off
on any mention of severe until 03 UTC Friday, and even considered
holding off until 06Z, but a few CAMS do depict convection
approaching the ND border by around 03 UTC. More discrete
convection is likely over north central and northeast Montana
this afternoon/evening and by the time convection moves into North
Dakota, we would expect a more of a MCS line segment. And the
later the convection, the more questions of how long it will hold
as we reach the diurnal lull of the morning hours, with a good
amount of capping. Most models end convection pretty quickly as it
passes through the northwest portion of the state.

.LONG TERM...(Friday through Wednesday)
Issued at 332 AM CDT Thu Jun 27 2019

Thunderstorm chances highlight the extended portion of the
forecast as well.

Depending on how convection plays out late tonight, expect we will
have at least some early morning convection to deal Friday
morning. The ECMWF is much more bullish in holding onto convection
through the morning hours and bringing it farther south, to around
Bismarck by midday. The GFS/NAM pretty much kill off any remaining
convection by 15 UTC, before it exits the northwest part of the
state. But then again, we get almost a repeat of Thursday with
mostly dry conditions during the day, and convection firing over
eastern Montana, and waiting to see if it hold together as it
moves into western ND. The ECMWF is again the farthest south with
convection and holds onto it longer Saturday morning. The NAM/GFS
and Global Gem all seem to hold onto the stronger capping and keep
most of the convection confined to the northwest part of the
state, and Canada.

On Saturday, the upper ridging over the area finally breaks down
as a shortwave lifts from the northern Rockies into southern
Canada and an associated cold front pushes through the forecast
area. It will become very unstable along and ahead of the cold
front on Saturday. A limiting factor will be very warm air aloft,
capping convection. It will be quite hot and humid Saturday
afternoon, especially around the James River Valley. We could
possibly be needing headlines for a Heat Advisory. A little too
early now, but with this type of instability due to the increasing
low level moisture, there will be a conditional threat for severe
weather based on the CAPE available. Eventually cooler air aloft
makes it way into the area late Saturday, but it`s possible that
the front will be through our area. Needless, we will keep a
mention of severe for Saturday with a loaded gun type sounding
over the eastern portions of the forecast area.

We return to more of a quasi-zonal flow through the remainder of
the long term period. Thus not quite the heat and humidity, but
the threat of thunderstorms will remain in the forecast.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 332 AM CDT Thu Jun 27 2019

Mainly VFR conditions expected through the forecast period. Kept a
VCTS along southern TAF sites. For now we did not mention thunder
as there remains some uncertainty in how far north convection will
make it, but will continue to monitor. Possibility of a MVFR
ceiling/vsby in a thunderstorm for southern TAF sites. Otherwise,
after convection exits this morning, expect VFR conditions
through the remainder of the forecast period.

&&

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

&&

$$

SHORT TERM...TWH
LONG TERM...TWH
AVIATION...TWH


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