093
FXUS63 KBIS 300926
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
426 AM CDT Tue Apr 30 2024

.KEY MESSAGES...

- Widespread rain showers are expected to move across the state
  from west to east through the day. A rumble or two of thunder
  is possible.

- Windy across southwest North Dakota today, with critical fire
  weather conditions expected in the afternoon and early
  evening. A Red Flag Warning has been issued.

- Daily chances (low to medium) for rain (and maybe an isolated
  thunderstorm or two) through the rest of the week, with
  temperatures slightly below normal.

&&

.DISCUSSION...
Issued at 425 AM CDT Tue Apr 30 2024

An upper level ridge axis will continue to move off to our east
early this morning while western and central North Dakota
settles into southwest flow aloft. A surface cold front is
currently located near the Montana/North Dakota border and this
boundary will cross this state from west to east this morning
and afternoon.

Widespread rain showers will accompany the cold frontal passage
with radar returns now currently approaching the Montana/North
Dakota border. Some of the CAMs have been aggressive in ramping
this activity up in the 12 to 14 UTC time frame and beyond,
even suggesting the potential for some embedded lightning
strikes. That being said, instability will be limited as the RAP
is only showing the potential for a couple hundred J/kg MUCAPE.
Still, an embedded rumble of thunder or two isn`t out of the
question and much of the forecast area has been highlighted in a
general thunderstorm outline by the Storm Prediction Center.

We will clear out rapidly late this morning and early afternoon
across the west behind the front, especially the southwest
where modest pressure rises and cold air advection will lead to
some gusty west northwest winds. These winds will team up with
the dry airmass behind the front to usher in some near critical
to critical fire weather conditions across the southwest and
portions of the south central. See the Fire Weather section
below for more details.

Most of the rain will move out to the northeast by late this
evening. The heaviest totals continue to look probable across
portions of the northwest and north central where the NBM is
suggesting a 40 to 60 percent chance of a half inch of rain or
more. The NBM suggests that almost all of western and central
North Dakota has a 50 to 90 percent chance of a quarter inch of
rain or more. The one exception will be across the far southwest
and south central where probabilities drop off quickly.

Most will see a break in rainfall on Wednesday but we could see
some lingering showers across the far north. The next wave then
rotates around the very slow moving upper low that will be
centered near the Montana/North Dakota/Saskatchewan border by
Wednesday night. We will then see our next round of low to
medium rain shower chances Wednesday night through at least
Friday, if not Saturday, as the upper low slowly moves across
the region. Thursday looks to be the wettest day of the
aforementioned period and the NBM suggests that much of the
central and southeast could see a medium chance for another
quarter inch of rain or more on Thursday. We will also start to
see a bit more instability towards the middle to end of the week
so some more isolated thunder will be possible as well.

Regarding temperatures, we will see highs close to normal for
this time of year on Wednesday, ranging from the upper 50s
northwest to the mid 60s southeast. However, in the Thursday
through Saturday time frame, we will be a bit cooler than normal
with highs mainly in upper 40s to around 60. The NBM then
suggests a return of highs in the mid 60s to lower 70s range by
Sunday and Monday. That being said, considerable ensemble spread
continues to be noted this far out.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 100 AM CDT Tue Apr 30 2024

An upper level disturbance and surface cold front will cross the
state from west to east Tuesday morning and afternoon, bringing
widespread rain showers and MVFR to IFR ceilings. MVFR
visibilities will also be possible under any heavier showers.
Winds will shift to out of the northwest behind the front,
becoming gusty across most of the west. Sustained winds will
approach 30 mph with gusts to 40 mph over portions of the
southwest Tuesday afternoon. Winds will decrease fairly quickly
Tuesday evening. Most areas will see improvement into VFR
categories (from west to east) late Tuesday afternoon and into
the evening.

&&

.FIRE WEATHER...
Issued at 425 AM CDT Tue Apr 30 2024

A cold front will cross the state from west to east this morning
and afternoon. While the passage of this boundary will bring
widespread rain showers to much of western and central North
Dakota, the lowest chances for wetting rains will be across the
southwest. A dry airmass will then push into the southwest
behind the cold front by mid to late morning, rapidly clearing
any lingering cloud cover out. Winds will also increase with
sustained winds up to 30 mph and gusts to 45 mph by the
afternoon hours. With the gusty winds and a dry airmass in
place, locations that experience little to no wetting rains
should dry out quickly.

If the wetting rains are limited in coverage across the
southwest as expected, then the winds will overlap with low
afternoon humidity (values dipping as low as 18 percent) for
three hours or more across significant portions of Bowman,
Adams, Hettinger, Slope, Golden Valley, Billings, and Stark
counties. For these factors, we decided to go ahead and upgrade
these counties to a Red Flag Warning today from 1 PM MDT to 8 PM
MDT. It was decided to not upgrade Grant and Sioux counties but
we could still see a couple hours of near critical fire weather
conditions here this afternoon and we will message the potential
in the Hazardous Weather Outlook.

As a final note, the northern portions of Golden Valley,
Billings, and Stark counties may only see near critical fire
weather conditions. Critical fire weather conditions may be
confined to southern portions of these counties.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 1 PM this afternoon to 8 PM MDT this
evening for NDZ031>033-040-041-043-044.

&&

$$

DISCUSSION...ZH
AVIATION...ZH
FIRE WEATHER...ZH