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Office: BIS

FXUS63 KBIS 232003
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
303 PM CDT Sat Jun 23 2018

.SHORT TERM...(This evening through Sunday)
Issued at 301 PM CDT Sat Jun 23 2018

Forecast highlights in the short term period will again be shower
and thunderstorm chances tonight and Sunday.

Thunderstorms continued to develop with the heating of the day.
We expect thunderstorms to continue to develop and become more
numerous with time this afternoon into early evening. Heavy rain
should be the main threat with the relatively slow-moving storms.
There is also a possibility of weak funnel clouds which may touch
down briefly, as surface vorticity and surface to 3km CAPE values
have increased this afternoon.
the day.

Currently, weak upper level low pressure extended from northeast
Montana southeastward across North Dakota into northeastern South
Dakota. Meanwhile at the surface, an associated trough extended from
a surface low over eastern South Dakota northwestward across North
Dakota into northeast Montana. While there is plenty of MUCAPE
across the area, but weak 0-6km bulk shear exists. Precipitable
water values around 1-1.3 inches is well above the average. The
overall threat for severe storms (large hail, damaging winds)
remains low, but the threat for scattered to widespread slow-moving
storms with heavy rain and small hail exists over our area this
afternoon and this evening during peak heating of the day, with
showers and thunderstorm activity becoming more scattered/isolated
later this evening into the overnight hours as peak heating
wanes.

Meanwhile farther west, a larger upper level low was developing
over western Montana and Wyoming. This low is forecast to
develop/move southeast into western South Dakota/Nebraska on Sunday.
This feature, along with the weak upper trough over North Dakota,
will continue to send upper level energy impulses rotating around
the larger low, with a very moist lower level (surface to h850)
moisture transport into the north central US states. Plenty of CAPE
but continued weak 0-6km shear will promote showers and
thunderstorms with a heavy rain threat rather than any severe
weather threat. By late Sunday morning into the afternoon hours, we
expect showers and thunderstorms to become more numerous/widespread.

Expecting lows tonight in the upper 50s to lower 60s, and highs
Sunday in the 70s.

.LONG TERM...(Sunday night through Saturday)
Issued at 301 PM CDT Sat Jun 23 2018

An active pattern remains over the Northern Plains through Monday,
as an upper level low/embedded S/WV trough moves from western
South Dakota/Nebraska Sunday night to the Minnesota/Iowa by
Tuesday morning. A series of embedded S/WVs will continue to
rotate through the Northern Plains, triggering showers and
thunderstorms with the most active periods again diurnally driven
like today, during the afternoon and evening hours. Flow aloft
remains weak so the main threat with any of the stronger storms will
remain locally heavy rainfall.

As this upper low continues moving east on Tuesday, another upper
level low centered over northern British Columbia/Alberta on Tuesday
moves east across central Canada through next week.

Tuesday...

Meanwhile across the northern tier of states, a set of upper level
impulses moves east across Montana daytime Tuesday, and across the
Dakotas Tuesday night. A surface trough and cold front will
accompany this set of upper level impulses, and should be the focus
of a chance of showers and thunderstorms Tuesday afternoon and
night. This scenario will be accompanied by better bulk shear values
(0-6km shear around 30-35 knots), so a few stronger storms will be
possible in North Dakota Tuesday afternoon and night.

Wednesday...

Zonal flow aloft and surface high pressure brings quiet weather to
the region on Wednesday.

Thursday through Saturday...

Another longwave trough sets up along the US west coast Thursday,
deepening and becoming a closed low over the US Rockies/Great Basin
on Saturday. This will keep southwest flow aloft over the Dakotas
during this period, and will bring a good potential for an active
round of showers and thunderstorms Thursday through next weekend.

Temperatures overall through the long term period will remain
seasonal for late June, with highs in the 70s and 80s and lows in
the 50s and 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1211 PM CDT Sat Jun 23 2018

Low pressure will move slowly east across central North Dakota
through the forecast period. Scattered to numerous thunderstorms are
expected to develop this afternoon over all of western and central
ND. VFR conditions are expected outside of thunderstorms but any
storm will have the potential for localized MVFR ceilings and
visibilities. Thunderstorm intensity and coverage will diminish by
mid evening. Increasing low level moisture today and tonight will
lead to areas of MVFR ceilings developing over southern North Dakota
Sunday morning. Will add a mention of MVFR ceilings along southern
TAF sites for now. Will not mention fog at this time but areas of
fog can not be ruled out either Sunday morning.


&&

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

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH



Office: FGF FXUS63 KFGF 232009 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 309 PM CDT Sat Jun 23 2018 .SHORT TERM...(This evening through Sunday) Issued at 309 PM CDT Sat Jun 23 2018 Showers and thunderstorms, their strength and coverage, will be the main issue for the period. Water vapor loop and rotation of the radar returns shows the main upper low is still to our southwest over south central ND/north central SD. There has been thunderstorm activity developing during the early afternoon hours across a couple of old boundaries. One lingering front in the Lake of the Woods area has created enough surface convergence for some slow moving thunderstorms. Another surface boundary stretching from the Devils Lake basin in to west central Minnesota has been the focus for additional thunderstorm development, with the greater coverage on the ND side. SPC meso page has a non-supercell tornado parameter around 4, and low level CAPE and surface vorticity are maxed out in that area. Surface vorticity is much weaker with the cells down in west central MN. Will have to keep a close eye for any funnel formation during the next few hours, but the RAP has the best vorticity moving away from the highest low level CAPE values by 21-23Z. The loss of daytime heating will reduce coverage of showers and thunderstorms as we head into the overnight hours. However, the weakening upper low will still be drifting eastward into the area and many of the high resolution models have lingering convective activity hanging around into 06Z and beyond. Best chances will be near the surface low in northeastern SD, so have some chance POPs lingering in our south and west with more isolated activity elsewhere. Temps should drop into the 60s overnight with at least some clearing. By tomorrow, the eastern upper low over our region will have weakened and merged with the western circulation moving from the Northern Rockies into the Northern Plains. More showers and thunderstorms will develop again by afternoon thanks to daytime heating, with the best chances in the southwest closest to the upper system. It looks to be a another day with decent instability (around 1000 J/kg of CAPE), but weak deep layer bulk shear. Temperatures should be a couple of degrees cooler than today thanks to cloud cover. .LONG TERM...(Sunday night through Saturday) Issued at 309 PM CDT Sat Jun 23 2018 Deepening upper low caught on the southern limb of split flow will slide to the south and east of the region Sunday through Tuesday. This will keep rain chances within the forecast Monday and Tuesday will keeping temperatures mild and skies cloudy. Areas that hold best chances for rain reside in the southern Red River Valley into west-central Minnesota. Thunderstorm chances Monday will be limited on these days due to clouds hindering diurnal destabilization and weak mid level lapse rates. A cold front slowly approaches from the west late Tuesday into Wednesday bringing the chance for scattered showers and thunderstorms. By mid week zonal flow aloft will set up transitioning to southwesterly flow towards late week. This will allow thunderstorm chances and the temperature trend to increase late next week. Surface high pressure behind Wednesday's stalling cold front should keep conditions dry for at least one day, progged to be Thursday. This is short lived as southwesterly flow aloft will swing embedded disturbances over the Northern Plains. There may be an uptick in strong to severe thunderstorm chances late next week as better wind shear associated with the aforementioned embedded disturbances develops over the Northern Plains along with the chance for instabiility and moisture content to grow over the area. A number of factors including frontal placement and shortwave passage timing will prevent any further details from being forecast at this time. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 102 PM CDT Sat Jun 23 2018 All sites are VFR, with scattered showers and thunderstorms developing across the entire forecast area. Continued trend of VCTS at all the TAF sites, and think ceilings will stay over 5000 ft. The storms are pretty scattered so will reserve prevailing thunder mention for any amendments. The convective activity will continue for much of the afternoon before tapering off in early evening. Most sites will be VFR overnight, although some MVFR clouds will move into the KDVL area towards morning. Winds direction will be pretty variable this afternoon with boundaries and convection nearby, but speeds will be mostly below 12 kts. More steady direction out of the east by the end of the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ SHORT TERM...JR LONG TERM...CJ AVIATION...JR