Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 251821
AFDFGF

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

.UPDATE...
Issued at 121 PM CDT Fri May 25 2018

Main adjustment was to expand mention of Iso Thunderstorms across
the RRV based on current radar/satellite trends. Atmosphere has
destabilizes along and east of surface trough and CU field has
expanded across our southeast. Organized large scale support is
lacking and ML CAPE is generally 500-1000 J/KG, so confidence in
higher coverage or a larger severe threat is limited. There is a
better chance for better synoptic support further north, but
any development there may be delayed until later. Profiles are
supportive of microburst potential with thunderstorm activity and
DCAPE reflects this with values over 1000 J/KG on RAP mesoanalysis.
If surface layer were realized (somewhat skeptical) the parcel
would tap into 2000-3000 J/KG of SB CAPE and a stronger updraft
could support isolated severe hail threat. For now severe threat
would be highly isolated whether it was wind or hail, but it
couldn`t be ruled out.


&&

.SHORT TERM...(Today and tonight)
Issued at 318 AM CDT Fri May 25 2018

Main concerns today will be the very warm temperatures and
isolated thunderstorm chances. Near critical fire weather
conditions will be an additional impact (see fire weather section
below).

Water vapor imagery indicates a lot of little disturbances
upstream. Guidance is keying in on one such disturbance that will
affect mainly northwest Minnesota during peak heating leading to
isolated thunderstorm chances. Instability and deep layer shear
should be relatively weak, but given inverted-V type sounding with
deep mixed layer a stronger wind gust possible with any storm.
Will also need to monitor the potential for an isolated storm
across the southern forecast area this afternoon with CAM guidance
indicating a few storms (possibly keying in on upper level energy
across western South Dakota).

Deep layered westerly flow will advect in a very warm airmass
today (850mb temps @+20C). Deep mixed layer expected with dry air
advecting to the surface. Given the strong mixing potential along
with the dry airmass, temperatures should be able to easily climb
into the 90s across most areas along and west of the valley
(Records highs are likely). Hot and breezy today.

.LONG TERM...(Saturday through Thursday)
Issued at 318 AM CDT Fri May 25 2018

An upper low over NV/UT area will keep northern tier under an upper
ridge through the weekend, with a weak wave bringing a chance of
showers and storms to central ND on Sunday, but weakening as they
move into the DVL area.  By Monday, we transition into a SW flow
aloft pattern as ridge flattens, with increasing chances of showers
and storms Sun night through Wednesday...with the upper trough
slowly lifting into MN by late Wed aftn.  Should see a break in
activity Wed night...although upper pattern is out of phase by 12Z
Thu and confidence decreases significantly for the end of the
week...but an eventual return to a SW flow pattern aloft will bring
more chances of activity from late in the week into the next
weekend. Primary challenges will be timing short waves embedded in
the SW flow throughout the period.  Temperatures will be warmest
this weekend, in the 80s and 90s, and decline to more seasonal temps
in the 70s and 80s for the work 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).


&&

.FIRE WEATHER...
Issued at 318 AM CDT Fri May 25 2018

Deep mixed layer this afternoon will lead to near critical fire
weather conditions across northeast North Dakota, with RH near
20% and westerly winds near 25 mph with stronger gusts. Elsewhere,
RH will be slightly higher and winds slightly weaker.

&&

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

$$

UPDATE...DJR
SHORT TERM...TG
LONG TERM...Speicher
AVIATION...DJR
FIRE WEATHER...TG


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