496
FXUS63 KFGF 070247
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
947 PM CDT Mon May 6 2024

.KEY MESSAGES...

- Strong southeast winds will continue this afternoon into
  tonight across eastern North Dakota and adjacent portions of
  Minnesota, with gusts up to 50 mph at times.

- Showers and isolated thunderstorms will affect the region through
  Wednesday.

&&

.UPDATE...
Issued at 947 PM CDT Mon May 6 2024

Wind speeds quickly dropped off at quite a few sites right
around 9 pm, so was able to cancel most of the Wind Advisory a
little early. Still have seen a few higher gusts in the Gwinner
to Valley City corridor, so kept the advisory going yet there.
Did see the latest observation at Gwinner really dropped now
too, so may be able to cancel the last 3 counties a little early
too. However, will wait for another round of top of the hour
observations before doing so.

UPDATE
Issued at 620 PM CDT Mon May 6 2024

No huge changes with this forecast update. Will slow down the
arrival of likely precipitation chances for another few hours.
Seems like there is more areal coverage of showers/storms
organizing over eastern South Dakota now, but if they hold
together as is, it will be a few more hours until they arrive in
the southern FA. There is some lightning activity over
southeast North Dakota, but nothing too concentrated or long
lasting. As the previous shift noted, 850mb winds crank up to
around 60 knots around or after sundown (and continue through
most of the night), so the echoes on radar are moving very
fast.

&&

.DISCUSSION...
Issued at 212 PM CDT Mon May 6 2024

...Synopsis...

A strong upper level trough is moving out of the Rockies into
the central and northern High Plains as seen on water vapor
satellite imagery. This is helping rapid deepening of a surface
low in the western Dakotas, generating an expansive increased
wind field as well as drawing in moisture and lift into the
region. By Tuesday afternoon, the upper trough closes into an
upper low, becoming stacked on top of surface low halting its
deepening/strengthening. This also allows the low to stall over
the Dakotas by Tuesday. A second upper trough moving through
the Intermountain West Wednesday will then help the upper low
move southeast out of the Dakotas by Wednesday night.

Northwest flow aloft then develops with the help of upper
ridging over the West around Friday, with ensemble guidance all
depicting an open, progressive shortwave trough moving out of
central Canada into the Upper Midwest. While there is strong
consensus in this synoptic wave, there are differing scenarios
in its progression and strength. Uncertainty in the upper
pattern then degrades after Friday`s shortwave passage with
either upper ridging out of the West becoming the dominate
influencing mechanism for our weather, or upper troughing over
the Great Lakes. Both would still favor average temperatures for
our area, however.

...Strong winds today and tonight...

Strong surface pressure gradient over our area and mixing of low
level winds in the 40-50 kt range is contributing to sustained
winds 25-35 mph with gusts up to 50 mph in eastern North Dakota
into portions of adjacent northwest and west-central Minnesota.
Southeasterly direction of winds is favoring strongest winds in
the southern Valley with the help of downsloping within the
southern Valley, as well as locally better mixing from daytime
clearing. This will continue advisory-criteria winds through the
afternoon into the evening.

After sunset, daytime heating ceases, although the pressure
gradient remains tightened over our area, along with some
continued mixing with the help of either downsloping/terrain
influences as well as transferred winds from aloft with the help
of convection/weak thunderstorms tonight. Still thinking winds
will remain near or at advisory-criteria after sunset until
around midnight. Winds aloft increase over 50 kt tonight, which
introduces some uncertainty in tapping into these near warning-
type criteria. However, the chance in seeing warning-criteria
winds is low, at around 10% between 7pm - 1am.

...Showers and thunderstorms through Wednesday...

Lift and strong moisture transport into our area gives high
confidence in widespread showers into eastern ND and west-
central and northwest MN. Weak instability feeding into this
moisture transport allows the chance for weak thunderstorms
tonight into Tuesday.

Tuesday midday, some high resolution guidance does bring a
surface front through into our area, coupled with relatively
warmer/more moist air mass. With forcing aloft and at the
surface from convergence and frontal lift amid surface CAPE
values 100-500 J/kg, clusters of semi-discrete and/or a line of
thunderstorms are expected. In this same area, low level winds
veer with height, with good ventilation aloft. Should
thunderstorms remain semi-discrete and attach themselves on the
boundary, funnels and/or a couple of quick tornadoes cannot be
ruled out. This conditional chance is low, less than 10%, but
still exists and would increase if more discrete mode and/or
greater instability becomes more favored. The window of
opportunity for such potential exists between 11am to 4pm.

Otherwise, accumulated precipitation is forecast to range in
the 0.20 - 0.75 inches, with locally higher amounts up to 1.5
inches in areas that see numerous rounds of showers and
thunderstorms.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 620 PM CDT Mon May 6 2024

This will be a challenging set of TAFs, due to wind speeds and
shower/isolated thunder chances. Also expect some LLWS around or
after dark (up to 60 knots), continuing through most of the
night. This amount of wind is not expected at the surface, but
surface winds will stay gusty the entire night and into Tuesday.
There could still be a few higher gusts at the surface
associated with some of the shower activity. TAFs are pretty
hard to write with showery convection, especially when it is
fast moving and fairly high based initially. Trying not to
include TEMPO groups every 4 hours as well. So will not be
chasing TAFs too much tonight, as precipitation will be off and
on. There may be some lightning around, but for the most part
expect showers. Ceilings do tend to lower at most sites during
the night (some closer to Tuesday morning), then lift again
Tuesday afternoon as the first main band of precipitation
either dissipates or moves into southern Canada.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Advisory until 1 AM CDT Tuesday for NDZ038-049-052.
MN...None.

&&

$$

UPDATE...Godon
DISCUSSION...CJ
AVIATION...Godon