853
FXUS63 KFGF 141800
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
100 PM CDT Wed Aug 14 2024

.KEY MESSAGES...

-Showers and thunderstorms will increase in coverage today and
 last into Thursday. Heavy rain and lightning are the main
 impacts.

&&

.UPDATE...
Issued at 100 PM CDT Wed Aug 14 2024

The initial cluster is lingering over the southern Red River
Valley with less activity farther east. The more organized
clusters/embedded thunderstorms remain along the theta-e axis in
central ND and that is slowly moving northeast. Latest CAMs are
doing a better job reflecting these trends, with activity
eventually filling in as the mid level low begins to organize
later this evening/overnight. RAP analysis continue to
marginal/elevated instability along our west along with weaker
shear and mode trends show this either holding as is or
weakening in time this evening. Severe potential locally appears
to be minimal, with skinny/marginal cores more likely than an
organized severe threat. THere is a subset of CAMs that show an
eventual linear MCS in SD moving "near" our southern CWA,
however even those CAMs show less supportive environment for
severe, so it will likely take some shifts in the surface
pattern to suet up a threat for more organized severe locally.
Worth monitoring in the 3hr mesoanalysis period, but right now
confidence in severe is limited.

Regarding heavy rain; latest HREF 6HR PMM has trended even
lower versus the last update discussion further lowering
confidence in excessive runoff potential outside an unlucky
track of a thunderstorm over urban areas.

UPDATE
Issued at 1021 AM CDT Wed Aug 14 2024

A cluster of showers/embedded thunderstorms have spread into
far southeast ND with isolated showers now along the Highway 2
corridor. More organized synoptic ascent doesn`t arrive until
later this evening/overnight, so we are in a pattern with
increasing deep moisture and smaller scale features leading to
harder to predict evolution/coverage within our forecast area.
Higher coverage is tending to be concentrated near several
boundaries(more obvious in wind/theta-e fields) near our south
and west of our CWA. At least for now HRRR (being a hot-start
CAM) is reflecting near term trends, but beyond the morning I
don`t have as much confidence in coverage/evolution. For now
I`ve made adjustments to better reflect near term trends, and
held off on any major adjustments beyond midday (blended
previous forecast).

Impacts in our area through midday are mainly moderate rain and
isolated lightning activity. As the deeper moisture plume
overspreads our area along with more organized ascent the threat
for heavy rain increases, though HREF PMM doesn`t show values
that raise concerns for our hydrological forecast area unless
the higher end values fell in a short enough period of time over
one of our towns/urban areas where there is poor drainage
conditions lowering confidence in more than localized/minor
impacts. Considering that, a watch is not being considered at
this time.


UPDATE
Issued at 643 AM CDT Wed Aug 14 2024

Still many different scenarios for today rainfall evolution.
There are some t-storms forming in central ND from Minot toward
Dickinson and they are moving north-northeast. Movement of this
activity this morning would keep majority of the activity west
of Devils Lake unlike what 00z HREF had and what QPF is based on
12z-18z. Meanwhile something new is in the picture which is an
area of showers moving north thru NE SD and this looks like will
enter SE ND. This feature is more like what the 00z/06z High
Resolution Canadian has but this model intensifies it over
Jamestown today and has very little precip DVL region. So still
no clearer in what path todays rainfall will take. Hence why we
have pops in most areas thru today.

&&

.DISCUSSION...
Issued at 351 AM CDT Wed Aug 14 2024

...Synopsis...

500 mb low moving slowly east/northeast thru west
central/central Saskatchewan with one area of concentrated
t-storms in that area. In our region though a second weaker
upper low is over parts of Oregon/Idaho with a broad 500 mb
ridge into Minnesota. This puts our area in southwest flow aloft
and within this flow there are numerous short waves seen on
water vapor this early morning. How these short waves move and
bring development of showers/t-storms is the main forecast
challenge. PWATS are near 2 inches in a zone over central SD/ND
and this ribbon of deeper moisture slides slowly east today but
basically remains in the Devils Lake-Jamestown-Bismarck region
thru this evening.

Thunderstorm/heavy rainfall situation today remains typically
uncertain. HREF and various CAM guidance highlight what is the
most likely scenario which is t-storms from NW SD or SE MT
moving northeast and developing within this deeper moisture area
toward Devils Lake during the course of the day. Latest HRRR
backs off on timing and focuses it more into DVL region midday
vs WPC/HREF had higher precipitation 12z-18z today. At this
point and time, either scenario is just as likely. Not much
development in central ND at 08z but as short wave from NW SD/NE
MT moves northeast rapid development of t-storms may occur and
bring the heavier rainfall this morning or wave is slower to
move and slower to develop t-storms and main rain is midday or
afternoon into Devils Lake area.

Either way...idea is for the concentrated area of showers and
t-storms in central ND into Devils Lake area to advance east in
time into the Red River valley late today/this evening and into
NW MN tonight...though with lower intensity rainfall.

With high PWATS localized rain amounts 2-3+ inches are possible
in the zone thru central ND into Devils Lake basin. Uncertainty
is high enough though and also past 7 day NDAWN precipitation
for the area shows little to no precipitation for most of the
Devils Lake area. Thus feel going with a flood watch before
storms form is not quite the way to go due to prior conditions
have been mainly dry weather.

Thursday will see 500 mb trough to our west slide over eastern
Dakotas/Minnesota with Global Canadian and ECMWF developing a
closed low aloft vs GFS is more progressive. 00z ECMWF remains
more consistent from run to run and at this time favored in
developing area of rain around the upper low into parts of E
ND/RRV and much of northwest MN Thursday on backside of the
upper low. Not a heavy rainfall but a general rain area. If more
progressive GFS is right then rain area Thursday is less and
ends as system moves east.

Weekend into early next week shows an upper level ridge building
into south central Canada and northern Plains. 00z operational
GFS is a complete outlier compared to the 00z GFS ensemble and
discounted at this time. It has an upper low in NW Ontario into
Manitoba vs a ridge. Net weather result with a ridge would be
temps more into the low 80s. Some risk of a shower/t-storm early
and mid next week due to short waves moving.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 100 PM CDT Wed Aug 14 2024

Several cluster of showers are moving into southeast ND and
west central MN, with larger areas of showers/embedded
thunderstorms still over central ND which should eventually
slide east. Eventually the system should fill in with numerous
showers across eastern ND and northwest MN later this
evening/tonight, but thunderstorm coverage remains a question
for most sites. Winds initially are gusty from the southeast,
but as the surface low shifts east tonight they will tend to
become lighter and variable before north-northwest winds develop
Thursday at KDVL by late morning.


&&

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

&&

$$

UPDATE...DJR
DISCUSSION...Riddle
AVIATION...DJR