Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 271125

Area Forecast Discussion
National Weather Service Grand Forks ND
625 AM CDT Sun May 27 2018

Issued at 625 AM CDT Sun May 27 2018

Convection continues to display a weakening trend as it outruns
the area of better instability and enters a more stable airmass.
Most areas within the FA should receive measurable rainfall and
increased PoPs accordingly. Wind gusts up to 50 mph, small hail,
and brief heavy rainfall the main impacts over the next 1-2
hours considering the current environmental setup. Wind gust
threat will gradually diminish through the morning hours.


.SHORT TERM...(Today and tonight)
Issued at 350 AM CDT Sun May 27 2018

Severe thunderstorm potential the main concern today and tonight.
Currently, radar imagery indicates a convective complex (with
severe wind gusts) across central North Dakota propagating toward
this forecast area. Water vapor indicates upper level energy
responsible for this complex, with associated 50 kt 850mb
jet/strong warm air advection the main forcing. Mesoanalysis
indicates MUCAPE 1000-2000 J/KG across southwest/south central
North Dakota into South Dakota. Instability will advect to
northeast through the morning. Given the type of forcing, feel
confident that this complex will hold together in some form as it
moves through this forecast area. With that said, the forcing
should outrun the instability and anticipate a weakening trend as
it moves eastward. Mainly sub-severe storms expected this morning.

After this system moves through this morning, a boundary will set
up somewhere across the southern forecast area this afternoon,
with very hot temperatures (95+ degrees) and gusty southerly
winds to the south of this boundary. Not exactly sure where this
boundary will be at peak heating. Moderate instability and deep
layer shear along this boundary could lead to a few severe storms,
should storms be able to initiate this evening/overnight. This
initiation will be dependent on timing of any shortwaves within
the southwest flow aloft. Most CAM guidance does indicate a
stronger storm or two. This fits with SPC marginal risk for
severe storms.

.LONG TERM...(Monday through Saturday)
Issued at 350 AM CDT Sun May 27 2018

Upper ridge continues to slide east/break down as a series of vort
maxes embedded in SW flow aloft move into the central and eastern
Dakotas.  A frontal boundary stretched along the ND/SD state line
and into w cntrl MN will lift north into sern ND Mon evening as bulk
shear increases mainly over s cntrl ND...bringing an increased
threat for severe weather.  While SPC has the majority of the CWA in
a marginal risk, the location of best shear and boundary indicate
Ransom/Sargent counties would have the highest chance...although
still several periods out, leading to uncertainty.  Will not add any
mention of svr to extended grids at this time.  Series of waves and
periods of storms/more active weather continues through mid week
before main trough moves east of area Wed evening and next short
wave ridge aloft will bring a break in the active weather.  The dry
weather should hold in place through Thursday, however upper level
pattern reverts to SW flow aloft by early Friday morning...and a
continuation of embedded shortwaves bringing another active pattern
develops for Friday through next weekend.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 625 AM CDT Sun May 27 2018

Showers and a few rumbles of thunder will affect all TAF sites at
some point this morning. After this activity moves through,
anticipate the remainder of the period to be quiet and VFR.
Isolated to scattered thunderstorms are possible this evening and
overnight, but confidence is low as to how widespread this
activity will be. One last item to be aware of is the potential
for gusty southerly winds at KFAR this afternoon.


Issued at 350 AM CDT Sun May 27 2018

By the afternoon hours, a boundary will set up somewhere across
the region, with very hot temperatures (95+ degrees), low RH
values (@25%, possibly lower than 20%), and gusty southerly winds
(up to 25 mph) to the south of this boundary. There could be a
period of critical fire weather conditions if wind speeds are
greater than anticipated, which is possible considering potential
of winds mixing to the surface. Not exactly sure where this
boundary will be at peak heating today.




LONG TERM...Speicher
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