337
FXUS63 KFGF 062008
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
308 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.

&&

.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 /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 212 PM CDT Mon May 6 2024

VFR conditions will continue through 00Z before lowered CIGs in
the MVFR to eventual IFR categories moves over the region
between 00Z-12Z. This is due to a strong low pressure system
moving through the Dakotas, contributing to strong southeast
winds 20-30kt, gusting to 40 kt. Between 00Z-12Z, low level wind
shear is also expected to develop. This will also bring rain
showers to the region after 00Z, with embedded thunderstorms
possible. Confidence is still not high enough to introduce -TSRA
mention at any site, however.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Advisory until 1 AM CDT Tuesday for NDZ006>008-014>016-
     024-026>030-038-039-049-052>054.
MN...Wind Advisory until 1 AM CDT Tuesday for MNZ001>004-007-027-
     029>031-040.

&&

$$

DISCUSSION...CJ
AVIATION...CJ