Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 182042

Area Forecast Discussion
National Weather Service Grand Forks ND
342 PM CDT SAT JUN 18 2016

.SHORT TERM...(This evening through Sunday)
Issued at 342 PM CDT Sat Jun 18 2016

Convective timing and severity continues to be the primary
challenge for the period.

Showers that none of the high res models handled all that well
are finally weakening and exiting the eastern CWA. The high res
NAMRR and a couple of the HopWRF members break out some convection
behind these showers later this afternoon. However, the HRRR and
RAP keep that period dry. SPC meso page has only some limited
CAPE in our far southeastern CWA and with the shortwave that
brought the showers pulling away we will be in a general area of
subsidence. However, there is a weak warm front coming in so will
keep some low POPs going just in case something isolated develops.
Deep layer bulk shear will be improving throughout the night so
will have to watch in case anything does develop, but think the
main show will be later tonight.

The next shortwave trough coming over the top of the upper ridge
will move across southern Canada towards the Manitoba/Ontario
border by morning. Surface low pressure will deepen over the high
plains tonight and then take off along the international border,
bringing the warm front north overnight and then the cold front
down through our CWA on Sunday. The low level jet will be ramping
up and feeding right into the surface low, bringing plenty of
moisture and allowing deep layer bulk shear to get up into the
50-70 kt range. NAM has MUCAPE values getting into the 2000-3000
J/kg range, and even if it is overdone that should be plenty to
keep storms going as they push east from the high plains
overnight. A severe MCS seems likely, just a question of the
track. The 12Z NAM and GFS along with some of the morning high res
runs were trending north of the border with storms, but the more
recent HRRR runs are back to tracking the convection through
northern ND. Will keep the forecast of highest POPs and severe
potential in the northern counties through late tonight into
tomorrow morning.

That first shortwave trough moves off to the east Sunday, but a
stronger wave begins to move towards southern Manitoba during the
day. The cold front will be moving down through the CWA during the
morning and early afternoon, just a question of how fast and will
there be ongoing convection or destabilization along the boundary.
Warmer mid level temps moving in may keep the southern counties
capped, and some models don`t put out much precip. However, there
is a lot of instability and deep layer shear as well as low level
VGPs for rotation. Have some POPs into Sunday afternoon
redeveloping along the southern CWA.

.LONG TERM...(Sunday night through Saturday)
Issued at 342 PM CDT Sat Jun 18 2016

Following the passage of a cold front on Sunday afternoon... the
early week period looks to transition from a zonal H5 flow pattern
to a low amplitude northwest flow pattern ...with somewhat dry and
seasonably mild conditions expected. A surface high pressure area
transits the area from Monday into Tuesday so that northerly surface
winds eventually turn from the south early on Wednesday.

A warmer and more moist southerly return flow shows up on
Wednesday... with a corresponding shortwave trov riding the flat H5
ridge in from southern Sask by midday. longer range models both
bring scattered tstms across the area during the day on Wednesday...
but with the Low Level Jet shunted more towards the mid Mississippi
and Ohio Valleys... neither widespread severe weather nor heavy rain
appear likely.

The GFS and ECMWF are a bit out of synch from Thursday into
Saturday... with the GFS bringing a fairly robust shortwave trof and
closed low across the area again on Thursday while the ECMWF stays
with a much weaker open wave. Both stay mainly dry into Fir and
Sat... with only widely scattered tstms expected. Current fcst
package favors the drier ECMWF for now.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1241 PM CDT Sat Jun 18 2016

VFR conditions continue with showers and thunderstorms in the
central TAF sites. The activity should spread northeastward
towards KBJI in the next hour or so, and the precip at KGFK and
KFAR will only last a few more hours. There should be a bit of a
break in convection before the next, stronger round arrives late
tonight and early Sunday. However, with uncertainties in the exact
track of the system and many solutions keeping best coverage north
of the international border, will hold off on any later period
vcts for now. Cigs should remain VFR, but there could be a period
of LLWS as the low level jet ramps up from the south during the
early morning hours. The LLWS will decrease by mid morning, but
surface winds will pick up out of the south to southwest (west at
KDVL) and gust above 20 kts by the end of the period.


.FGF Watches/Warnings/Advisories...


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