Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 191724
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1224 PM CDT Sat Aug 19 2017

.UPDATE...
Issued at 1223 PM CDT Sat Aug 19 2017

A surface low was centered over the border of central
Saskatchewan/Manitoba, with a trough extending south near
Tioga/Stanley to near Dickinson and Hettinger. A cold front extended
from the low southwestward to near Sidney Montana and Beach ND to
Miles City in Montana. Dewpoints were lowering west of the trough,
with relative humidity values in Beach at 21 percent with a
northwest wind at 16 mph. As the trough and cold front move
east/southeast across the state, drier air will push into the state.
The current red flag warning seems warranted.

Even though the cold front is a bit slower than forecast, it will
not alter much in the way of temperatures expected today. Only
delayed increase in winds in central ND would be affected.

UPDATE Issued at 850 AM CDT Sat Aug 19 2017

Quiet weather continues this morning. Only change needed to
forecast was to increase cloud cover a little bit over the west to
address some high clouds moving through.

UPDATE Issued at 614 AM CDT Sat Aug 19 2017

Current forecast trending ok with no changes to previous forecast
other than updating current conditions.

&&

.SHORT TERM...(Today and tonight)
Issued at 315 AM CDT Sat Aug 19 2017

Concerns for the short term include critical fire weather
conditions southwest for low humidity and gusty west winds this
afternoon and early evening. For this have issued a red flag
warning for the southwest.

The upper air pattern depicts a rapidly moving shortwave trough
pushing onshore across the western US and Canada. Downstream this
feature is forcing a resulting short wave ridge across the
northern plains. Subsidence associated with the ridge will set up
a warm thermal profile across western North Dakota today. A dry
cold front will enter the northwest by late morning reaching the
central by this evening.

While the consensus temperature forecast from Forecast Builder
for southwest and central North Dakota gives upper 80s to lower
90s, have continued raising high temperatures today about 2 to 3
degrees across this area. This is supported by the warmer HRRR as
well as the GEFS temperature plumes which place a preponderance of
runs with highs in the mid 90s central.

With this very warm air the RAP model soundings support mixing to
nearly 700 MB so expect mixing winds to become west around 20 mph
with the frontal passage.

By Saturday night the shortwave trough will push through and bring
sufficient cyclonic flow aloft to support widely scattered
thunderstorms across the southwest after midnight.

.LONG TERM...(Sunday through Friday)
Issued at 315 AM CDT Sat Aug 19 2017

Relatively fast and weakly cyclonic flow associated with the
shortwave will bring scattered thunderstorms across mainly central
and southern North Dakota Sunday and Sunday night lingering into
Monday.

This will be followed by a building H500 ridge across the western
US Tuesday through Friday. For the most part the northern plains
will remain on the eastern flank of this ridge maintaining
moderate temperatures in the 70s and mid 80s with low chances for
precipitation.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1223 PM CDT Sat Aug 19 2017

VFR conditions expected through the forecast period.

&&

.FIRE WEATHER...
Issued at 315 AM CDT Sat Aug 19 2017

A cold front will move across northwestern North Dakota late
this morning, then sweep southeast across central and southwestern
North Dakota in the afternoon before reaching the James Valley
Saturday evening. South to southwest winds ahead of the front will
shift sharply to the northwest at 20 mph, with gusts to 30 mph.

The cold frontal passage and associated wind shift and gusty winds,
in combination with minimum relative humidities between 11 and 15
percent, high temperatures in the upper 80s to lower 90s, and dry
fuels, will produce critical fire weather conditions from late
Saturday morning through early Saturday evening in southwestern
North Dakota. Thus, a Red Flag Warning has been issued. Please see
the Fire Weather Forecast at www.weather.gov/bis for more details.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for NDZ031>033-040-
041-043-044.

&&

$$

UPDATE...JV
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...JJS
FIRE WEATHER...KS/WAA



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