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000
FXUS63 KBIS 151954
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
254 PM CDT Mon Apr 15 2024

.KEY MESSAGES...

- Multiple rounds of showers are likely (60-80% chance) tonight through
  Tuesday night, with a few thunderstorms possible (30%
  chance). The highest precipitation chances are across central
  and eastern North Dakota. Severe weather is not expected.

- Low afternoon humidity and gusty southeast winds will lead to
  near critical fire weather conditions this afternoon across
  the south.

- Cooler temperatures start on Tuesday and will continue into
  the weekend. The coldest days will be Thursday and Friday when
  highs will mainly range from the mid 30s to mid 40s.

- Some light snow is possible Wednesday night through Friday,
  mainly across the north (30% chance). Little to no
  accumulation is expected.

&&

.DISCUSSION...
Issued at 254 PM CDT Mon Apr 15 2024

This afternoon, a deep upper low was moving across the Rockies,
while a surface low had formed on the lee side, in northeast
Colorado. A secondary low was analyzed in northeast Wyoming but
is starting to merge with the main low. There have been two main
rounds of precipitation that have come from the secondary low,
with a few marginal impulses moving through aloft. One area is
now in eastern North Dakota, while the second is moving through
central North Dakota. Although SPC mesoanalysis indicates
instability is quite low, we have had a few isolated
thunderstorms in this second area over the past couple of hours.

A Wind Advisory remains in effect for parts of southern North
Dakota, with sustained winds up to 30 mph and gusts up to 55.
Somewhat inverted V soundings and scattered rain showers are mixing
down stronger than expected wind gusts, with a few observed gusts in
excess of 60 mph earlier today. We did issue a Special Weather
Statement for counties surrounding the Wind Advisory for
occasional gusts up to 55 mph.

We are expecting a break in precipitation late this afternoon
and evening before showers and a few thunderstorms become more
widespread late tonight and through Tuesday as the deep Colorado
low pushes northeast. NBM QPF probabilities have stayed
relatively consistent over the past couple of days, with a high
probability of at least 0.50" of rain for areas from Bismarck
to Rolla and east. Probabilities quickly drop off the further
west you go, with only a low chance for even 0.10" in far
western North Dakota. The various deterministic models are
advertising pretty different solutions when it comes to the
environment tonight and tomorrow, but the general expectation is
for a few hundred J/kg of CAPE at most late tonight into
Tuesday which would support a few thunderstorms. High-res output
paints a similar picture, with potentially a few storms moving
north from South Dakota where the environment is more supportive
of convection. Any thunderstorms that do develop could lead to
locally higher rain amounts.

Precipitation chances taper off from west to east Tuesday night
into Wednesday as the Colorado low moves off to the northeast.
Meanwhile, a secondary deep trough and attendant low will drop south
from British Columbia and Alberta Tuesday into Wednesday. Ensemble members
continue to favor a slightly northern track to this system that
keeps the bulk of precipitation in the southern Canadian
Prairies. This system will also bring a push of colder air for
the end of the week, with 850mb temperatures cooling down to 5
to 10 degrees C below zero. This will translate to highs
Thursday and Friday in the mid 30s to mid 40s, with overnight
lows in the 20s, potentially even the teens in some of our
normal cold spots. We continue to carry a 20 to 30% chance of
precipitation across mainly northern North Dakota Wednesday
night into Friday, with snow the predominant expected
precipitation type. However, little to no accumulation is
expected.

Winds are expected to stay elevated through the week as the Colorado
low wraps up and deepens as it moves northeast, although the ECMWF
EFI is less bullish on the upper end potential compared to the past
few days. On both Wednesday and Thursday, strong northwest
winds are forecast, with sustained speeds in the 20 to 30 mph
range, potentially a little higher.

There is fairly good agreement on flow aloft turning more quasizonal
over the weekend and into next week, allowing warmer air to slowly
return to the region. NBM temperature percentiles show a steady
warming trend through Monday, with low chances of precipitation
returning to the forecast then as well.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1242 PM CDT Mon Apr 15 2024

Showers and a few thunderstorms will continue across much of
central North Dakota into this evening, with a break in
precipitation expected. Rain chances increase after 06Z with
rain likely at all terminals Tuesday morning except KXWA. There
is low confidence in where and when we will see a few isolated
thunderstorms through the period. VFR ceilings will persist
until around 12Z, when a broad area of MVFR to IFR ceilings
expand north across the forecast area. Southeast winds will stay
breezy to windy through the night tonight. Rain showers have
been occasionally mixing down wind gusts up to 50 knots. Towards
the end of the TAF period, winds will decrease and begin to turn
northerly at western terminals.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 11 PM CDT /10 PM MDT/ this evening for
NDZ034>036-041-042-044>047-050.

&&

$$

DISCUSSION...Jones
AVIATION...Jones