Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 220309
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1009 PM CDT Fri Apr 21 2017

.UPDATE...
Issued at 1001 PM CDT Fri Apr 21 2017

Weak shortwave energy and surface convergence near developing
low pressure and an approaching cold front is occurring over
northeast Montana. This has produced some lightning over the past
few hours as convection tracks across far northeast Montana. Did
add some small pops far northwest ND to account for this late this
evening. Think thunder will have ended by then.

Otherwise no significant changes to the going forecast. updated
pops with latest consensus blend of short term models, which was
not much change from the previous forecast. Kept a mention of
patchy fog also across the far north. Updated text products will
be sent shortly.

UPDATE Issued at 640 PM CDT Fri Apr 21 2017

High pressure over central North Dakota will move slowly southeast
tonight. Light and variable winds with mostly clear skies tonight.
A cold front will drop south into the area bringing increasing
clouds from north to south during the day. No significant changes
to the going forecast at this time other than populating latest
sensible weather elements.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 258 PM CDT Fri Apr 21 2017

Latest GOES16 mid level water vapor and visible imagery indicates
the mid/upper level high was centered over northeast South Dakota
this afternoon, while the surface high pressure resided over
Streeter ND, in Stutsman County. Large fair weather cumulus field
dominated south central ND and the James River Valley. Elsewhere
sct/bkn cirrus clouds were becoming dominant in western ND along
with a few fair weather cumulus underneath. Dry weather will persist
through the evening, then the high pressure area is squashed
farther south through the short term period. Heights and thicknesses
lower from north to south through Saturday, in response to a surface
cold front and associated shortwave now located over south central
Saskatchewan and into Manitoba. This cold front will slide into
northern ND 09z-12z Saturday, gradually sagging into central ND
21z Sat-00z Sun. Will add some patchy fog late tonight into
Saturday morning, along and just behind the cold front in far
northern ND including the Turtle Mountains. This has support from
the HRRR and RAP13. With the thickness packing/baroclinic zone
remaining along and north of Interstate 94 through 00z Sunday,
expect much warmer conditions across southern ND versus northern
ND. Main impact in southern ND with the proximity of the sagging
cold front in the afternoon will be some increase in cloud cover.
Highs Saturday will range from the 40s north, to the mid 60s
south. The NAM/GFS QG fields shows the best alignment/overlap in
forcing, 850-700mb frontogenetical forcing and 500-300mb synoptic
scale ascent, resides over northern ND. Pops/rainshowers essentially
stretch and increase from Renville County east to Rolette County,
and south into Wells County through Saturday afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 258 PM CDT Fri Apr 21 2017

The front/baroclinic zone sags into northern South Dakota Sunday,
with the area of forcing mentioned in the short term discussion
continuing over north central ND. Ascent does spread a bit farther
south, along and north of a line from Williston to Jamestown
Saturday night through Sunday. Some concern for minor snowfall
accumulations Saturday night and into Sunday morning along and
north of Highway 2 where up to one inch of snowfall is forecast
before the precipitation mixes with and changes back over to
rainshowers in the afternoon. Main effect across southern ND
Sunday will be more cloud cover and cooler temperatures, but
remaining dry through the day. Highs across the north Sunday
continue in the upper 30s to lower 40s, while mid 50s to lower 60s
occur in the south.

Once the baroclinic zone slips into South Dakota Sunday, we really
never recover back into the 60s for the rest of the long term
period. An active/cooler period ensues with periodic chances of
rain/snow. Sunday night through Monday will be our next round of
precipitation. Accumulating snow of another inch is possible
across northern ND from late Sunday night through Monday morning.
Elsewhere precipitation will fall as rain. Highs Monday will range
from the upper 30s north to lower 50s south. Tuesday will be the
coldest day with highs generally in the 40s across western and
central ND. Precipitation chances will mainly be confined to
western ND Tuesday and Wednesday.

Will need to monitor at least one potent system ejecting across
the Central Plains and possibly curling back into the northern
plains Thursday through Friday. Both the ECMWF and GFS spread
precipitation across western/cental ND, but the GFS is more widespread
and heavier with precipitation amounts versus the ECMWF. Main
reason is because the Operational/Deterministic GFS track brings
the low pressure into ND, while the ECMWF track is farther east.
The GFS Ensemble Mean favors a track farther south and east from
the Operational GFS. Thus, at this time, perhaps one would lean
towards more of a ECMWF solution. Highs during this period remain
in the 50s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1001 PM CDT Fri Apr 21 2017

A cold front will move south through the northern TAF sites of
KMOT and KISN tomorrow. This will bring a chance of MVFR ceilings
and a few sprinkles to KISN and KMOT Saturday morning. Mesoscale
and global models are in pretty good agreement bringing the cold
front through KISN and KMOT around 15 UTC. What they do not agree
on is the amount of low level moisture with the front. Currently
the mesoscale models bring MVFR-IFR clouds into the state
quickest, while the NAM and especially the GFS hold off on
bringing lower ceilings south. lower ceilings can be seen across
southern Canada and clouds will make it south to at least the
northern TAF sites. For now though, just brought MVFR ceilings
for a period to KMOT Saturday morning, before raising to VFR.
Winds will shift north to northeast behind the cold front.

&&

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

$$

UPDATE...TWH
SHORT TERM...KS
LONG TERM...KS
AVIATION...TWH


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