Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 272347

Area Forecast Discussion
National Weather Service Bismarck ND
647 PM CDT FRI MAY 27 2016

Issued at 637 PM CDT Fri May 27 2016

Weak surface low pressure over the eastern Dakotas and upper level
low pressure along the Canadian border is keeping scattered
showers and isolated thunderstorms mainly over northern and
eastern ND this evening. Adjusted pops based on latest radars and
time lagged short term guidance. Areas of fog this morning and
models indicating low stratus dropping south into the state
tonight. Think there may be some patchy fog ahead of any stratus.
Numerical guidance is also indicating some morning fog. Will add
a mention in the text products over central ND.


.SHORT TERM...(This afternoon through Saturday)
Issued at 339 PM CDT Fri May 27 2016

Mid/upper level closed low seen on water vapor sat pics over
southwestern Manitoba/Turtle Mountains area this afternoon. Current
convection in the form of scattered showers were in southern
Saskatchewan/Manitoba and the northern tier of counties in North
Dakota near the vicinity of the upper level low.

Plenty of low level moisture and surface heating was associated with
the well-developed cumulus field over western and central North
Dakota. Forecast soundings indicated the potential for
showers/thundershowers over all areas...and Bowman radar was
detecting some showers from south of Medora to Bowman and south into
northwestern South Dakota.

No severe weather is expected given the weak bulk shear. Surface
CAPE values were in the 250 J/Kg range in our south central...up
to 1000 J/Kg in northwest and north central North Dakota. Across our
northern counties there is a potential for more vigorous
showers/thunder with the cooler air aloft near the upper low. Thus
showers that do form in the afternoon and early evening hours (with
the help of surface heating) would have sustained support from aloft.

Tonight the upper level low is forecast to open and become diffuse
with time as it lifts northward into northern Manitoba/Saskatchewan
on Saturday. Meanwhile a large scale upper level low system over
British Columbia today expands eastward tonight...sending the
leading edge of an upper level vorticity impulse wave eastward
across Montana and reaching western North Dakota Saturday afternoon.
Thus the chance of showers and thunderstorms increases in western
North Dakota Saturday afternoon. No severe weather is expected with
cape and shear values on the weak side.

.LONG TERM...(Saturday night through Friday)
Issued at 339 PM CDT Fri May 27 2016

A dry and stellar day Sunday...but good chances of widespread
thunderstorms on Memorial Day - especially in the afternoon and
Monday night with potential for strong to severe storms highlight
the long term.

Saturday night the upper low continues moving northward...with
chances of showers and thunderstorms in the evening...with
decreasing chances late night.

Sunday appears to be the only day with little to no chances of
showers or the British Columbia low remains stationary
and no energy impulses are forecast moving through North Dakota.
Partly to mostly sunny skies with highs in the mid to upper 70s will
make for ideal outdoor events.

Sunday night and Memorial Day Monday the British Columbia low begins
to move/develop southeast...moving across the rockies Sunday night
and sending the first in a series of upper level waves into the
western plains. Confidence for the most widespread and potentially
severe event continues to be Monday afternoon in the west...and
Monday night over all of western and central North Dakota...with the
best instability over the southern part of the state.

Good chances of widespread showers and thunderstorms continue into
Tuesday and Wednesday with the upper low developing into an open wave
and moving across Montana, Wyoming, and the Dakotas...but the threat
for severe storms is limited.

A better chance of a dry period Thursday and Friday with more of a
zonal west-to-east flow aloft.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri May 27 2016

Models indicate low ifr-lifr stratus dropping into northern TAF
sites of KISN and KMOT after midnight. Latest iterations of short
term guidance also bring mvfr-ifr into KJMS and nearly KBIS and
KDIK. for now will limit ifr mention to KISN and KMOT. Kept a vcsh
this evening at KISN and KMOT. Could be some patchy fog Saturday
morning but not thinking widespread enough at this time to add a
mention at any TAF site. Showers and thunderstorms will move into
western north dakota Saturday afternoon.


.BIS Watches/Warnings/Advisories...


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