Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 220429
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1129 PM CDT Wed Sep 21 2016

.UPDATE...
Issued at 1129 PM CDT Wed Sep 21 2016

Latest water vapor loop and 00z GFS indicates an shortwave over
northern ND getting ready to exit into southern Canada within the
next few hours. Only update was to extend a mention of isolated
showers into Bottineau county for the next couple of hours, until
the shortwave moves north of the border. Otherwise the previous
trend of decreasing pops across the north continues. A few more
shortwaves migrate into ND from southeast Montana and western
South Dakota overnight; however continued northeast winds will
keep low level dry in place for all but far western ND, and inhibit
showers from reaching the ground, if any develop. The HRRR does
indicate isolated showers after 12z in eastern MT and far western
ND, and this is handled well in the going forecast.

UPDATE
Issued at 917 PM CDT Wed Sep 21 2016

Increased POPs a bit northwest to account for an area of light to
moderate rain moving through. Otherwise the forecast remains on
track.

UPDATE
Issued at 639 PM CDT Wed Sep 21 2016

Inherited forecast is on track, with no major edits for the early
evening update. Main update was to trend down on POPs north to
more scattered/isolated wording.

&&

.SHORT TERM...(This evening through Thursday)

Issued at 312 PM CDT Wed Sep 21 2016

Concerns for the short term focus on the chance for rain and
amounts.

This morning an h500 upper low was just off shore from the
Pacific northwest. The low is forecast to deepen and dig southeast
into the Great basin region by Thursday evening with an associated
h500 downstream ridge forming over the northern plains. At the
surface, high pressure remains in place across southern Canada
with developing low pressure across the central plains. This
weather pattern will introduce some forecast complexities with
dry low level northeast flow limited precipitation and the h500
ridge keeping the upper low track more to the west. So initially
the chances for precipitation will be limited to the far west and
northwest portion of the state tonight and Thursday. Lows tonight
will be in the 40s to around 50 and highs Thursday in the 60s
except 50s northwest.

.LONG TERM...(Thursday night through Wednesday)
Issued at 312 PM CDT Wed Sep 21 2016

Above average uncertainty in the extended picture. Initially the
upper low becomes negatively tilted and lifts out through the
northern plains into Canada. This will be active for showers and
scattered thunderstorms for Friday into Saturday as the low lifts
through. Will add thunderstorms to the forecast Friday and
Saturday central and east.

A blocking ridge downstream will keep the low from cleanly
exiting the region. The models now, especially the GFS, deepen the
upper low and dumbbell it around the region Monday and Tuesday
forming a REX Block. There is much uncertainty here as the Ecmwf
does not initially agree, but eventually both models end up with a
giant Rex Block over the northern plains by Wednesday. The main
take away will be above average uncertainty in temperature and
precipitation early next week. For now have stuck with the
superblend guidance which gives scattered showers and highs mainly
in the 60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1129 PM CDT Wed Sep 21 2016

Low vfr cigs/3500ft agl expected at KISN at times this taf period.
Showers possible at KISN between 17z and 21z Thursday. Otherwise
cigs based between 6kft to 11kft at all other terminals. Northeast
winds will become easterly after 12z Thursday, generally ranging
between 15kt and 25kt.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...KS
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...KS



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