Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 191800
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
100 PM CDT Wed Jul 19 2017

.UPDATE...
Issued at 1255 PM CDT Wed Jul 19 2017

Updated SPC products confirm the main threat for severe today is
well south. Updated DSS and top news of the day info. Now the main
short wave is moving into the RRV attm. Clearing noted behind this
wave into central ND and with enough sfc heating to nr 80 degrees
this aftn and dew pts in the mid 60s 2000-2500 j/kg cape likely
mid aftn behind this wave. So likely some re-development of scat
storms mid to late afternoon eastward into the RRV, but strength
and coverage remain uncertain as upper levels showing mid to upper
level drying behind the short wave and lack of upper level
support. However at the low levels have a boundary moving in and
probably enough to trigger a few storms. Mainly a non-severe event
unless conditions change drastically. The various HRRR/WRF and CAM
models remain rather poor in their forecasts for convection.

&&

.SHORT TERM...(Today and tonight)
Issued at 348 AM CDT Wed Jul 19 2017

Shortwave energy moving east into North Dakota from Montana will be
the initial focus for thunderstorm chances this morning. Favorable
effective shear and moisture and modest instability reside in
western ND, in closer proximity to the surface low, allowing for
storm development early this morning. Expect initial isolated to
widely scattered storms to form in north central North Dakota,
gradually tracking east into the Devils Lake basin area and
northeast North Dakota early this morning. The CAMs indicate that a
few strong to severe thunderstorms are possible in this area with
the main threats being hail to one inch in diameter and gusts to 60
mph.

By mid to late morning, surface based instability will begin
development and the warm front will begin working north into the
southern Red River valley. Additional shower and storm development
in central North Dakota will gradually move into eastern North
Dakota. Many CAMs suggest this development will eventually collide
with warm front forcing in the central valley, yielding thunderstorm
activity strengthening into the strong to severe discrete cells and
eventually a complex of storms moving southeast through the southern
Red River valley in the afternoon. These discrete cells and complex
would have the strongest threats with hail over 2 inches in
diameter, damaging gusts to 75 mph, and tornadoes possible. Heavy
rainfall is a notable concern as well with precipitable water
values maxing at 1.5 to 2.0 inches this afternoon, especially over
areas in west central MN that received several inches of rain
recently. Additionally, there is some potential for additional
storm development behind the main complex in the middle to late
afternoon in the central to southern Red River valley, but this is
very uncertain at this time.

.LONG TERM...(Thursday through Tuesday)
Issued at 348 AM CDT Wed Jul 19 2017

Thursday-Friday...Weak ridging within zonal flow will lead to a dry
day on Thursday with temperatures near to above normal values.
Return flow commences Thursday night with weak shortwaves possible.
For Thursday night, most guidance suggests axis of instability will
remain across western North Dakota and that any early morning
activity should be weakening as it enters eastern North Dakota.
Although details are still uncertain, the potential does exist for
strong to severe storms Friday afternoon/evening as the axis of
instability propagates over the region with strong deep layer shear
in place.

Saturday-Monday...A stronger upper level wave will propagate
southeast across Canada into the Great Lakes region. This will
spread a cooler and drier airmass into the region. A few showers
will be possible across northwest Minnesota Saturday afternoon.
The airmass behind this system will be much cooler, and ridging
will lead to below normal temperatures on Sunday and Monday (with
dry weather).

Tuesday...Most guidance is in agreement suggesting upper flow
becoming zonal with the next series of upper waves bringing shower
and thunderstorm chances.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1255 PM CDT Wed Jul 19 2017

VFR anticipated thru the pd. Cloud bases remain aoa 8k ft. Early
aftn winds the main issue as localized wind gusts from the south
to 20-30 kts at times on the north edge of the stratiform area
moving thru wc MN early aftn.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

UPDATE...Riddle
SHORT TERM...BP
LONG TERM...TG
AVIATION...Riddle


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