400
FXUS63 KBIS 171711
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1211 PM CDT Thu Aug 17 2017

.UPDATE...
Issued at 1204 PM CDT Thu Aug 17 2017

Still keeping a close eye on the southwest this afternoon.
Utilized a blend of current guidance with HRRR dewpoints to get
some lower dewpoints over the southwest this afternoon and also
expanded the area of sub 20% RH a little farther east. Winds
continue to be marginal but if we do get some convection this
afternoon we could see local erratic and gusty winds.

Otherwise, we adjusted pops a little. Latest iterations of the
mesoscale models look to be a little slower than our given pop
guidance and also maybe a little more in agreement in isolated
convection late this afternoon and early this evening over the
southwest, then hinting at stronger convection tracking from the
northwest/north central this evening into eastern ND overnight.
Have adjusted pops to account for this.

UPDATE Issued at 950 AM CDT Thu Aug 17 2017

Made some minor updated for sky cover and removed mention of fog
for the remainder of the morning. Mesoscale models continue to
hint at possible convection northwest this afternoon so added a
slight chance here which matches up well with WFO GGW.

Will keep an eye on lowering humidities and increasing winds over
the southwest this afternoon.

UPDATE Issued at 632 AM CDT Thu Aug 17 2017

Current showers appear to be diminishing but area of clouds
continues to expand east. Clouds may inhibit fog from forming east
this morning. Otherwise current forecast looks ok.

&&

.SHORT TERM...(Today and tonight)
Issued at 313 AM CDT Thu Aug 17 2017

A surface low pressure across eastern Montana is forecast to move
to central North Dakota tonight then into eastern North Dakota by
Friday morning. Aloft, a significant shortwave over Minnesota
will lift northeast into the Great Lakes region by tonight
leaving broad cyclonic flow aloft over the Northern Plains in its
wake. The combination of surface trough and weak cyclonic flow
aloft will combine to support widely scattered thunderstorms today
and tonight across west and central North Dakota.

Ahead of the surface trough today a thermal ridge associated with
a weak EML will move to western North Dakota supporting warm
temperatures close to 90 southwest. The HRRR RH values fall close
to 15 percent across much of the west central and southwest this
afternoon. Clouds could be the one limiting factor for high
temperatures today but don`t believe there will be enough cloud
cover to hold back temperatures too much.

Tonight, the model consensus supports 20 to 30 POPs across
central North Dakota, in the form of showers and widely scattered
thunderstorms. Severe weather is not expected.

.LONG TERM...(Friday through Wednesday)
Issued at 313 AM CDT Thu Aug 17 2017

The extended forecast begins Friday with a shortwave ridge
bringing warmer temperatures Friday and especially Saturday.
Highs should be in the 80s Friday with more widespread lower 90s
by Saturday. This will be followed by a Pacific cold frontal
passage cooling the region back into the 70s and lower 80s Sunday
through Tuesday. This will also bring a chance for scattered
showers and thunderstorms Sunday and Sunday night. Broad ridging
develops aloft by early to middle of next week suppressing
convection and returning warmer temperatures to the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1204 PM CDT Thu Aug 17 2017

Regarding a wind shift:
Low pressure trough oriented N-S along the border of MT and ND at
18z will move eastward across KISN/KDIK this afternoon, and becoming
nearly stationary across central ND near KBIS/KMOT this evening,
reaching near KJMS by 12z Friday morning. South/southeast winds
ahead of the trough should become northwesterly behind the trough.

Regarding thunderstorm hazards:
Isolated thunderstorms possible at KISN/KDIK aft 21z, better chances
of thunderstorms at KMOT aft 00z, with isolated thunderstorms
possible at KBIS and KJMS later tonight.

VFR ceilings and VSBYS expected at all TAF sites.


&&

.FIRE WEATHER...
Issued at 313 AM CDT Thu Aug 17 2017

While there are some fire weather concerns today critical fire
weather conditions are not expected.

A warm thermal ridge will support high temperatures today around
90 southwest into west central North Dakota. While consensus
models show Minimum RH values around 20 percent opted to use the
dryer HRRR model which supports Minimum RH`s as low as 15 percent.
A wind shift to the Northwest is forecast with the surface trough
passage this afternoon. Again, raised winds a tad over consensus
to around 15 mph with gusts 20 to 25. Based in this there should
not be sufficient winds to create critical fire weather
conditions today.

However another warm day is forecast Saturday with a more
significant frontal passage late Saturday afternoon and night.
This period will be monitored for possible critical fire weather.

&&

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

$$

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