Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 221138
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
638 AM CDT Thu Sep 22 2016

.UPDATE...
Issued at 635 AM CDT Thu Sep 22 2016

A few very light rain showers continue to slowly slide through
far southwest North Dakota, otherwise quiet weather continues.
Have adjusted precipitation chances a bit to account for these,
otherwise the remainder of the forecast remains on track.

&&

.SHORT TERM...(Today and tonight)
Issued at 259 AM CDT Thu Sep 22 2016

Latest water vapor imagery shows the well advertised closed upper
low circulating over southwest Oregon, with the attending trough
extending down through western California. A 120kt jet streak
was riding down on the back side of the upper low which will
continue to dig the upper low/trough through Nevada and Utah. The
upper low will become negatively tilted as the jet streak rounds
the base of the trough, with a compensatory downstream mid/upper
ridge across central/eastern ND through tonight. A deformation
zone initially will set up over north central Montana today and
tonight, resulting in the location for the heaviest precipitation.
Some precipiation expected in western ND today and tonight,
becoming more widespread Friday and shifting into central ND, as
the upper low begins to eject out from Utah toward North Dakota.

For today, just the west will have pops representing isolated to
scattered showers, while elsewhere, low level northeast flow will
transition to an easterly flow between 15kt and 25kt. This will
yield an upslope component, especially across the west aiding in
the clouds and shower development. Mid/upper level ridging will
keep central ND dry today with a mix of sun and clouds. Highs
today will range from the upper 50s west to mid 60s south central.

For tonight, clouds increase across the rest of central ND, with
showers increasing and beginning to impinge into central ND.
Expect likely showers west with scattered showers developing
central late tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 259 AM CDT Thu Sep 22 2016

Friday through Saturday will represent the wettest period with
widespread showers. Highest probability for scattered
thunderstorms most likely Friday night, on the heels of a strong
low level southerly jet. Elevated cape limited to between 200 and
500 J/kg, however that might be compensated by 30kt to 45kt of
0-6km shear that is advertised per NAM/GFS. Will need to monitor
this period for any changes in instability/cape. Otherwise,
thunderstorm chances begin to shift east into the James River
Valley Saturday afternoon as the greatest cape/shear reside in
this area ahead of an advancing cold front. Still expecting a dry
slot to form southwest into south central Saturday, which will
limit precipiation chances somewhat. Gusty westerly winds are
forecast to develop in southwest ND Saturday afternoon, followed
by windy conditions Sunday west and most of central ND. Potential
wind headlines may be needed for events.

Sunday through Wednesday, possibly trending drier. Per WPC`s
Extended Forecast Discussion - which essentially has little or no
confidence on any one solution due to so much change over the past
few days in both the deterministic and ensemble guidance. Case in
point, the latest ECMWF is now back to a more progressive pattern,
whereby the weekend upper level low shifts into Manitoba and then
across Ontario, resulting in a dry pattern Monday through Wednesday.
The GFS is slower to shift the upper low east, holding onto precipitation
Monday into Monday night, then drying things out for Tuesday and Wednesday.
With so much uncertainty and low confidence, current gridded data remains
in good standing.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 635 AM CDT Thu Sep 22 2016

Isolated rain showers possible west today, spreading easterly and
increasing in coverage overnight. VFR conditions will remain today
into this evening, with localized MVFR cigs developing after
midnight.

&&

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

$$

UPDATE...JJS
SHORT TERM...KS
LONG TERM...KS
AVIATION...JJS



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