← Previous April 15, 2024 10:04 AM

FXUS63 KFGF 151504
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1004 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 1000 AM CDT Mon Apr 15 2024

Light rain is moving into eastern ND with the help of upper
level divergence and 700 mb warm air advection with
frontogenesis. This activity will slowly push east through the
day. Dry air in the lower levels will limit the amount of rain 
making it to the surface, keeping amounts under quarter of an 
inch today.

Overall, the 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...CJ
DISCUSSION...DJR
AVIATION...MM