Area Forecast Discussion
Issued by NWS Bismarck, ND

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155
FXUS63 KBIS 252308
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
608 PM CDT Wed Apr 25 2018

.UPDATE...
Issued at 608 PM CDT Wed Apr 25 2018

Only minor changes were made with this update, mainly to increase
sky cover through the evening in respect to the expansive high-
level clouds that are shifting east ahead of a middle- and upper-
level shortwave trough which has its axis along a Glasgow to
Billings, MT, line as of 23 UTC per GOES-16 imagery. The cold
frontal zone accompanying that shortwave is shifting southeastward
with time and is through Crosby already. Upstream observational
trends, the 18 UTC GFS and NAM, and recent rapid-refresh CAMs are
relatively lackluster with post-frontal shower potential, which is
consistent with forecast soundings that call for a dry sub-700 mb
layer persisting even behind the frontal passage despite
increases in overall tropospheric water content. We chose to leave
forecast PoPs largely as-is with this update, but they could need
to be reduced in a later update, especially over southwestern ND.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 215 PM CDT Wed Apr 25 2018

Spotty post-frontal rainshowers this evening and tonight with
gusty winds.

Collaborated with FGF and ABR to increase post-frontal winds this
evening and tonight using a HRRR/CONSShort blend as forecast BUFR
NAM/GFS soundings show an uptick in winds about half a kilometer
above the surface. These gusty winds are expected to mix down.

In addition to a brief period of gusty winds behind the cold
front, there will also be a chance of fast-moving spotty
rainshowers this evening across the northwest, moving south and
east through the night. A rumble of thunder cannot be ruled out in
heavier rainshowers, however the coverage of possible thunder is
very limited with low confidence. Forecast BUFR NAM/GFS soundings
show CAPE near zero with weak mid-level lapse rates between 4 and
6 degrees C/km where charge separation occurs. Low-level lapse
rates are a bit higher, however omega is positive at lower levels
with little moisture. For these reasons, probabilities of thunder
have been decreased to zero across all of western and central
North Dakota this evening and tonight.

Tomorrow looks to be dry and mostly sunny as a ridge begins
building in from the west. Some fair-weather cumulus clouds will
likely develop in the late morning and afternoon from daytime
heating.

.LONG TERM...(Thursday night through Wednesday)
Issued at 215 PM CDT Wed Apr 25 2018

Above average temperatures continue through Monday, peaking on
Sunday with highs in the upper 70s to around 80 degrees.

Expect dry weather with mostly clear skies across western and
central North Dakota from Thursday night through Sunday as a
strong ridge sits over the Northern Plains. This will lead to a
warming trend for the weekend, with temperatures peaking on Sunday
to near 80 degrees as the ridge axis moves over North Dakota with
breezy southwest winds.

Chances for rainshowers and a few thunderstorms return Sunday
night through Tuesday morning as an upper level low swings through
North Dakota, bringing sufficient moisture/lift/instability with
it.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 608 PM CDT Wed Apr 25 2018

VFR conditions are expected through the 00 UTC TAF cycle. A cold
frontal boundary will sweep southeast across the region tonight.
Winds will shift to the north behind the front and could gust up
to 30 kt for a 1 to 3 hour period immediately behind the frontal
passage at any given location. A few showers are also possible
with the frontal passage, but confidence in their occurrence is
waning. Mid- and high-level clouds will rapidly decrease by 12
UTC as the front continues moving away from the area.

&&

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

$$

UPDATE...CJS
SHORT TERM...TK
LONG TERM...TK
AVIATION...CJS



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