959 
FXUS63 KFGF 080910
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
410 AM CDT Fri Oct 8 2021

.SHORT TERM...(Today through Sunday)
Issued at 345 AM CDT Fri Oct 8 2021

Impacts in the short term will be rainfall coverage and amounts
through the weekend along with severe potential Saturday. Today
will see increasing cloud cover as moisture continues to pool
ahead of and along an inverted sfc trough across eastern ND.
Elevated instability will fuel shower and possibly some embedded
thunder as a band of precip is expected to develop within the 500
to 1000j/kg of MUCAPE. This band is expected to impact areas 
mainly along and north of the Hwy 200 corridor today and gradually
spread to the east into NW MN this afternoon. 00Z HREF 
probability matched means indicate a half to one inch of localized
rain is possible in the northern valley by this evening. 

A wide temp gradient is expected across the FA today with temps
holding below 60 in the northern Devils Lake basin on the cool
side of the slowing moving boundary with temps around 80 in the 
southern valley where some more sun is expected. 

Friday night into Saturday morning a brief lull in activity is
expected before a potent short wave brings another more pronounced
period of showers and storms. Depending on cloud cover and
instability ahead of the track of the surface low pressure there 
is potential for severe storms on Saturday across much of the 
area. Impressive shear values ahead of the surface low and along
the warm front indicate the potential for strong low level shear, 
rotating updrafts and supercellular characteristics leading to a
rare October severe weather potential day for the northern 
plains. As highly anomalous moisture, PWats around 1.5" which
occurs roughly once in ten years at this time of year per GEFS
climate return intervals, wraps into the approaching 500mb wave 
overrunning the northward advancing warm front, highly efficient 
precip rates will occur with the strongly forced environment. 
Models are in fair agreement with track and location of the 
deformation zone rain band tracking across ND Saturday evening 
into Sunday with widespread rainfall amounts occuring. With the 
spotty nature of the showers and storms ahead of the upper low
highly variable amounts area expected but with the backside 
precip band rainfall most areas are likely, 70%, to receive at 
least one inch with some locations, 10% chance, receiving up to 3
inches across the area by the time the rain departs Sunday.

.LONG TERM...(Sunday night through Thursday)
Issued at 345 AM CDT Fri Oct 8 2021

Focus within the long term was given mostly to analysis of forecast 
guidance regarding stout cyclogenesis within the central CONUS 
Wed/Thu. This may bring some impacts to the region through likely 
gusty winds and potential for a period of heavy rainfall.

Sunday - Tuesday: 
Saturday's shortwave trough will be exiting the region into southern 
ON on Sunday. There may be some lingering showers wrapped behind the 
exiting wave that continue at least through the first half of 
Sunday. Cooler air wrapping in behind the trough as well as clouds 
should help keep temperatures generally in the 60s, with breezy 
north winds making it feel a bit cooler. As the shortwave exits, 
southwesterly flow aloft redevelops as the amplified Rossby wave 
over NOAM recharges the pattern for the next wave break.

Wednesday - Friday: Ensemble guidance is in fairly good agreement of 
deep upper troughing near the Four Corners region to break eastward 
into the Central and Northern Plains mid next week. Consensus within 
guidance accompanies strong sfc cyclogenesis under this deep trough 
into the Northern Plains and Upper midwest. While exact location of 
this sfc feature is still in question, all guidance suggests the low 
will be well developed and matured by the time it reaches the 
Northern Plains. Because of its strength and expected stage in 
life cycle, we can draw out a few conclusions. 

First, strong cyclogenesis typically have gusty winds accompany 
them, and this case is no different. With the surface low likely to 
reach sub 990 mb, a tight pressure gradient surrounding the low is 
also likely which in turn brings high confidence in gusty winds both 
ahead and behind the low. What isn't certain is just how high winds 
may get, again owing to unknown sfc low trajectory through the 
Northern Plains. 

Second, with the mid lat cyclone likely near or undergoing 
occlusion, moisture should be well wrapping around the low, with 
long moisture fetch sourced from the GOM overspreading the FA within 
the cyclones warm conveyor/TROWAL. This also means the dry conveyor 
should be well under way bringing the potential for rain to quickly 
"turn off" from dry slotting. On the other hand, the cyclone could 
move through the Plains in such a way that deformation zone and 
residence time of steady rainfall still remains a potential 
scenario. These latter two features are again dependent upon the 
low's trajectory which still has a wide range of potential 
trajectories. Regardless, during the warm, moist conveyors passage 
(favored to be around Wednesday), steady rainfall is likely ranging 
from light to potentially heavy given forcing and moisture 
content/flux. Antecedent conditions primed by Saturday's heavy rain 
brings the potential for impacts from heavy rain, but uncertainty 
with Saturday's event as well as drought-laden soils currently in 
place further complicates flooding potential. Thus potential impacts 
from heavy rainfall Wednesday into Thursday has lowered confidence.

Third, with the system well wrapped up into Thursday, lingering 
showers on the backside of the cyclone is likely. Colder air behind 
the low is also expected, although not expected to create any precip 
type issues, at least during the period of higher precip. Still, 
colder air will bring temperatures towards seasonal normals with 
highs in the 50s and 60s and lows in the 30s to 40s. This brings the 
chance for patchy frost/freeze late next week.


&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1113 PM CDT Thu Oct 7 2021

Have stuck with the previous set of TAFs for the most part, with
the main themes being highly questionable rain/thunder chances,
the potential for MVFR/IFR ceilings late tonight into Friday, and
the fog potential overnight around KBJI. Will still only mention
any rain at KDVL and KGFK, although it could affect other sites
late tonight into Friday...it is just pretty hard to nail it down
too far out. KFAR may be the only site that does not deal with 
lowering ceilings late tonight into Friday. Did mention some fog 
at KBJI overnight through the early morning hours of Friday. For 
the most part, wind speeds will stay much lighter throughout.


&&

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

SHORT TERM...JK
LONG TERM...CJ
AVIATION...Godon