Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 252025

Area Forecast Discussion
National Weather Service Grand Forks ND
325 PM CDT Fri May 25 2018

.SHORT TERM...(This afternoon through Saturday)
Issued at 321 PM CDT Fri May 25 2018

Organized forcing is mainly north of our CWA with shortwave troughs
over southern Canada. Despite disorganized forcing locally,
instability, mid level moisture, and several weak surface
troughs/convergence zones have helped kick of isolated
showers/thunderstorms over parts of our CWA. Most CAMs show isolated
activity over much of our CWA, but HRRR does indicate maybe an
increase in coverage over NW MN. ML CAPE is still 500-1000 J/KG
limiting severe concern somewhat, but surface based parcels would
still feed into a very unstable air mass, so isolated/stronger cells
still can`t be ruled out. Moisture profiles (inverted-V) and DCAPE
over 1000 J/KG raises concern for microburst/downdraft potential
with activity, but without more organization threat should be very
localized/isolated. With marginal to unfavorable mid level lapse
rates and middling forcing activity should be highly diurnally
driven and wind down quickly after sunset.

Upper troughs are even further east on Friday, so other than Lake of
the Woods region, most locations should see dry conditions. Near
record or record highs are expected once again Friday with many
locations around 90F or warmer (a little "cooler" in the northern
RRV). As has been the case winds may also be underdone in guidance
based on mixing heights, so I trended winds up a bit from standard
blend towards MOS blend which has tended to be closer on wind
speeds (still a little low). Winds should be low enough and RH
high enough to keep us below RFW criteria, but it is worth
monitoring like today (could be "near" critical again).

.LONG TERM...(Saturday night through Friday)
Issued at 321 PM CDT Fri May 25 2018

Hot, possible record heat for Memorial Day Weekend. Cooler but still
above normal temperatures Tuesday through the rest of the next work
week. Chance for showers and thunderstorms in the Northern Plains
throughout the next week.

Upper level ridge with an upper low over the Nevada/Utah area
defines the upper level pattern at the start of the period. Some
embedded short waves will move over the area to help increase the
chances of showers and thunderstorms. Saturday night into Sunday
morning the east chance for shower and storms will be in eastern
North Dakota associated with a surface low to the southwest. Sunday
night the shower and rain threat increases as another surface low
moves in from the west. MU CAPE late Sunday could approach 1500 to
2000 J/kg. On Monday MU CAPE could be higher with values over 3000
J/kg in the NAM and GFS. Bulk shear over 40 knots also present in
the Northern Plains so there is severe potential with these storms.
One of the major limiting factors here will be the amount of CIN as
it is forecast to be high as well over this period.

Tuesday into Wednesday high precipitable water values in the NAM and
GFS are above the 90th percentile for nearby sounding climatologies
(BIS, ABR, and INL). This is supported by the previous upper low
becoming dislodged and the trough moving towards the Northern
Plains. Dryer weather expected Thursday before another chance for
rain late next week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1234 PM CDT Fri May 25 2018

VFR conditions will prevail through the TAF period across eastern
ND and northwest MN. Gusty westerly winds are expected this
afternoon, decreasing after sunset and becoming light (generally
5kt or less) during the night. Winds should then increase once
again late Saturday morning to 8-12kt range. Virga will be favored
later this afternoon mainly along and north of Hwy 2, though a
shower or even a high based thunderstorm can`t be completely ruled
out (confidence too low for inclusion in TAFs).




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