Area Forecast Discussion
Issued by NWS Bismarck, ND

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371
FXUS63 KBIS 240828
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
328 AM CDT Tue Oct 24 2017

.SHORT TERM...(Today and tonight)
Issued at 327 AM CDT Tue Oct 24 2017

Currently, a large low pressure system associated with our strong
winds on Monday was over the Great Lakes this morning, with a
building upper level ridge over the west coast and Rockies. Dry
westerly flow off the Rockies will make for a breezy day with
westerly winds of 15 to 25 mph. Seasonable temperatures with highs
in the 50s.

Tonight the western ridge continues to expand into our area with
warmer air aloft. West winds of 5 to 10 mph tonight will help keep
the lower atmosphere mixed enough for overnight lows in the upper 30s
to around 40F.

.LONG TERM...(Wednesday through Monday)
Issued at 327 AM CDT Tue Oct 24 2017

The main forecast issue in the long term period will be Fire
Weather issues on Wednesday, then very windy and turning much colder
with a chance of rain and snow Wednesday night and Thursday.

A Strong eastern Pacific Ridge and central and eastern U.S Trough
pattern maintains itself through the long term period. A couple
clipper type systems tracking through the ridge-trough pattern
will dominate our weather through early next week.

Wednesday: A vigorous shortwave trough moving through the upper
level flow over British Columbia Wednesday morning will move quickly
southeast across the southern Canadian Rockies and approach western
ND by Wednesday evening. This will induce a shortwave ridge over the
Dakotas during the daytime Wednesday, enhancing the warm airmass
over the Front Range and western plains, including North Dakota.
This will result in a mild west to southwest wind flow over our
area, with highs climbing into the 60s - and into the lower 70s in
southwestern ND.

Wednesday night and Thursday: The vigorous shortwave trough dives
southeast across the Dakotas. This strong system will induce and
deepen a surface low and associated cold front, which also tracks
southeast across our area Wednesday night. Strong cold advection, 3-
hour pressure rises of 5-9 mb and H850 northwest winds of 40-55
knots will make for another very windy period Wednesday night
through Thursday evening. It appears that we would likely need a
wind advisory for this time period. Timing of any wind headlines
will be determined by later forecast shifts. Lows Wednesday night
should be mainly in the 30s, but not much recovery on Thursday with
expected highs in the mid 30s to mid 40s across western and central
ND. Rain showers will mix with and turn to snow showers, with the
precipitation mainly falling north and west of the surface low. At
this time, precipitation amounts are fairly light according to model
consensus, resulting in light snow accumulations of mainly less than
an inch - and mainly in north central ND. The Turtle Mountains may
see an inch of snow.

The cold high pressure following the clipper system remains over our
area for a day or so. Lows Wednesday night are forecast to be in the
15F to 25F range; highs Thursday 35 to 40; then lows Thursday night
again 15 to 25 with another cool day Friday.

Warmer on Saturday and Sunday ahead of the next clipper system
moving through our area on Sunday night/Monday, bringing gusty winds
and chances of rain and snow showers.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1233 AM CDT Tue Oct 24 2017

VFR conditions are expected. Hazards to aviation include LLWS
at all TAF sites.

A fast moving weather pattern will bring a warm frontal passage this
afternoon as westerly downslope winds across montana will make there
way into North Dakota. Strong winds aloft will initiate some low
level wind shear beginning late this afternoon and continuing
tonight.


&&

.FIRE WEATHER...
Issued at 327 AM CDT Tue Oct 24 2017

Critical or near critical fire weather conditions possible on
Wednesday. A fire weather watch has already been issued for parts of
southwestern North Dakota valid Wednesday afternoon into early
evening.

On Wednesday we are expecting mild temperatures in the upper 60s and
lower 70s with minimum relative humidity values of 15 to 20 percent
over southwestern ND. These conditions combined with increasing west
winds in the 15 to 25 mph range will produce a period of critical
fire weather conditions Wednesday afternoon and early evening. Even
stronger winds are expected overnight Wednesday but humidities are
expected to increase during the evening behind a strong cold front.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Wednesday afternoon through Wednesday
evening for NDZ031>033-040-041-043-044.

&&

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...WAA
FIRE WEATHER...JV



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