Area Forecast Discussion
Issued by NWS Bismarck, ND

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084
FXUS63 KBIS 180445
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1145 PM CDT Tue Oct 17 2017

.UPDATE...
Issued at 1144 PM CDT Tue Oct 17 2017

Current surface analysis shows the potent cold front now through
central Saskatchewan into northeast Montana. Main adjustment this
forecast was to increase winds based upon upstream observations.
A couple peak gusts to 56kt occurred along and just behind the
front in southern Saskatchewan. Moose Jaw in Canada recently had
a peak of 71kt just as the cold front was moving through. Pressure
rises of 8mb to 9mb behind the front will continue to move
steadily east overnight. The HRRR wind gusts show a steady
decrease in the 50kt winds as they shift to the east over the next
few hours. Will maintain our wind advisory and update gusts to 55
mph. Updates forthcoming.

UPDATE Issued at 922 PM CDT Tue Oct 17 2017

Bumped up the winds and cloud cover a bit for tonight. This will
make temperature forecasting challenging as the winds are a big
determining factor in the temperatures tonight. With that said
left min temperatures alone as we already are a notch higher than
surrounding areas and cirrus will further thin out.

UPDATE Issued at 625 PM CDT Tue Oct 17 2017

Clear skies cover most of the region with some thin cirrus moving
into the the west. Update the winds a bit as the later
afternoon/early evening winds have been a bit gusty with good
linkage to winds aloft. Otherwise current forecast looks ok.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 214 PM CDT Tue Oct 17 2017

Strong winds tonight into Wednesday and potential critical fire
weather conditions Wednesday afternoon highlight the short term
forecast.

A strong cold front will enter western North Dakota between 05-07
UTC tonight, and propagate east into central North Dakota by
early Wednesday morning. Strong west to northwest winds are
expected behind this front. The main challenge is how mixed the
post-frontal surface to 825 mb layer will become tonight. The RAP
iterations through the day and 12 UTC NAM soundings at Williston
late tonight suggest that a small inversion may remain in place,
while the 12 UTC GFS has consistently shown near adiabatic lapse
rates throughout the layer. The GFS has also been consistently
stronger with its wind field, and would even support a small
window for gusts in excess of 50kts across northwest and north
central North Dakota late tonight into early Wednesday morning.
For now given uncertainty in mixing tonight, issued a Wind
Advisory for northwest and north central North Dakota into the
Upper James River Valley through Wednesday afternoon. Gusts of
45-50 mph are forecast. A local upgrade to a High Wind Warning
will have to be monitored based on upstream observations if
adiabatic lapse rates can be established during the night behind
the front.

See the Fire Weather Discussion below for details regarding
potential critical fire weather conditions on Wednesday.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 214 PM CDT Tue Oct 17 2017

Above normal temperatures Thursday and Friday highlight the
extended forecast.

An upper level ridge is forecast to build across the Northern
Plains and Upper Midwest Thursday transitioning to southwest flow
aloft on Friday. This favors an anomalously warm airmass
characterized by 850 mb mean temperatures between their 90-99th
percentiles for the period as forecast by the 00 UTC NAEFS. High
temperatures of 70 to 80 are forecast each day, above the 12 UTC
guidance consensus. A windy Saturday is possible behind a cold
front, which will have to be monitored for possible critical fire
weather conditions as fuels dry this week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1127 PM CDT Tue Oct 17 2017

The main hazard to aviation will be gusty surface winds late
tonight and Wednesday as a strong cold front sweeps through the
region. The strongest surface winds, 25KT to 45KT, are expected
across the north central and east, impacting KMOT- KJMS. Low level
wind shear is expected to impact all taf sites between 03z-15z.
VFR conditions will prevail for the 00Z forecast.

&&

.FIRE WEATHER...
Issued at 214 PM CDT Tue Oct 17 2017

A Fire Weather Watch is in effect for northern and much of central
North Dakota Wednesday.

For northern and much of central North Dakota, strong west to
northwest winds are forecast on Wednesday behind a cold front.
Sustained winds around 30 mph with gusts to 45 mph are forecast.
Afternoon relative humidity will fall to near 20 percent. While
high temperatures will only be in the 50s, dry and windy
conditions may lead to critical fire weather conditions across
northern and much of central North Dakota. Across southwest North
Dakota, winds will be weaker on Wednesday, sustained around 20 mph
with gusts to 30 mph.

Warm conditions are forecast again on Thursday and Friday with
highs of 70 to 80. However, winds are not expected to be strong
either day. A windy Saturday is possible behind a cold front,
however, there is some uncertainty if relative humidity will
reach critical levels.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Wednesday afternoon through Wednesday
evening for NDZ001>005-009>013-021>023-025-035>037.

Wind Advisory from 4 AM to 7 PM CDT Wednesday for NDZ003>005-
011>013-023-025.

Wind Advisory until 4 PM CDT Wednesday for NDZ001-002-009-010.

&&

$$

UPDATE...KS
SHORT TERM...PA
LONG TERM...PA
AVIATION...WAA
FIRE WEATHER...PA



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