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000
FXUS63 KFGF 151142
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
642 AM CDT Mon Apr 15 2024

.KEY MESSAGES...

- There is a 50% chance for areas to see greater than an inch of
  rainfall tonight through Tuesday night, with the highest
  chances across southeast North Dakota and west central
  Minnesota.

&&

.UPDATE...
Issued at 642 AM CDT Mon Apr 15 2024

A few locations started to report light rain totals in southeast
ND and with a more organized band forming (along the axis of
700MB frontogenesis) I felt comfortable increasing PoPs in the
morning hours, though actual totals should still remain light.
Otherwise, forecast remains on track.

&&

.DISCUSSION...
Issued at 354 AM CDT Mon Apr 15 2024

Shortwave ridging is building northeast this morning ahead of deeper
SW flow aloft over the central ROckies. Ahead of this mid level
shortwave ridge, an evelvated axis of WAA/frontogenesis and weak
instabilty (100-250 J/Kg) is supporting shower development and a few
non severe thunderstorms in southern ND moving into our southeast.
Soundings show a substantial dry layer above the boundary layer and
this has been limiting precipitation reaching the surface in our
area so far. Guidance still shows this axis moving up and over our
CWA south to north, with potential for up to 0.25" of rainfall I`m
skeptical of coverage regarding those amounts, considering the
10,000-12,000 FT dry layer in place all day and the lack of surface
reports so far.

Regarding Fire Weather Today: BL flow is out of the east-
southeast below this dry layer (with a shallower dry adiabatic
mixed layer than previous days). This is a traditionally moist
direction and guidance shows increasing mixed layer Tds within
this BL flow (surface Tds appear bot be reflecting this trend to
the south). This aligns with the area where increasing surface
gradient will bring increasing winds southwest to northeast, with
much lighter winds to the northeast of this moist axis. RH`s
should be much higher than previous days and increasing mid level
cloud cover could further limit mixing. Even in our northeast
where flow will be drier, cloud cover could limit potential highs
and it may be hard to see RH values at or under 25% without more
persistent afternoon clearing in our northeast (towards Lake of
the Woods). Even then, winds are significantly lighter there due
to weak gradient/mixed layer winds (5-10 mph, max 15mph).
Considering these trends I removed near critical messaging in our
south and held it out of our northeast.

Late tonight-Wednesday: The shortwave ridge swings east through this
evening with deep SW flow arriving later tonight, followed by the
actual mid/upper low passage Tuesday into Tuesday night. Surface
gradient increases and breezy to windy conditions are shown to
develop within the east-southeast flow. This isn`t a traditional
direction for good momentum transfer especially with shallower mixed
layers, though there is still a low probability (less than 20%) for
advisory gusts in southeast ND/west central MN. The shift in pattern
and arrival of the mid/upper low brings much deeper/moist air into
the region, with anomalous signals in specific humidity, PWATs, and
moisture advection between NAEFS/ECMWF/GEFS model climatology.
Deformation along an inverted trough axis rotating into our CWA will
be the focus for more widespread rain and embedded thunder mainly
during the Tuesday-Tuesday night period. Trend has lowered probs for
1"+ rainfall in the north (to less than 40%) with the best chances
for those amounts still mainly in southeast ND/west central MN and
this is likely a result of these amounts be tied to embedded
convective components which appear to be more favored farther south.

As this initial mid/upper low moves east a larger/colder mid/upper
low builds into the Canadian Prairies and Northern Plains Wednesday
into the end of the week. FOrcing/moisture becomes cutoff from or
region and ensemble trends have greatly reduced the probability for
measurable precipitation (low chances for very light rain/snow).
There is strong consensus on this track and impacts are not
expected, however there are variations regarding how strong this
mid/upper low center becomes as it transitions towards Hudson Bay
impacting CAA and potential for higher winds into the Northern
Plains.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 642 AM CDT Mon Apr 15 2024

VFR conditions are going to persist through the TAF period. The
timing of showers throughout the day will be difficult as there is a
dry layer that needs to saturate before rain will hit the airports.
Winds will primarily be out of the southeast during the day shifting
more easterly tonight. Also uncertain when the gusts break over the
TAF sites. KFAR for instance has kept gusts in a southeast wind
through the night while others keep to the diurnal trend.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...DJR
DISCUSSION...DJR
AVIATION...MM