Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 202019

Area Forecast Discussion
National Weather Service Grand Forks ND
319 PM CDT Fri Oct 20 2017

.SHORT TERM...(This evening through Saturday night)
Issued at 319 PM CDT Fri Oct 20 2017

Precip timing and placement will be the main forecast concerns for
the period.

Southwesterly flow aloft with a shortwave trough currently
entering the Central Plains, which will move quickly northeastward
into the Upper Midwest tonight, but the main upper trough will
remain to our west. The surface trough over the Northern Rockies
this afternoon will begin to enter the CWA by tomorrow morning.
The CAMs as well as the global models have been trending a bit
slower/further east with the showers associated with the lead
shortwave tonight. Only the GFS brings some precip into our far
southeastern counties around 09Z, with the other deterministic
models keeping us dry until after 12Z. Lowered POPs tonight to
just some low probabilities in the far east, but think there will
be better chances later during the day on Saturday as the main
upper trough comes out into the Plains. There is a fairly healthy
amount of QPF that develops across the eastern counties by
tomorrow afternoon as the main surface trough and cold front moves
into the area. There is a bit of negative Showalters so some
thunder is not out of the question and will keep an isolated
mention in the far east. There is also a decent signal for
another, weaker band of precip over the Devils Lake Basin
associated with some mid level frontogenesis. All of the precip
will weaken and push eastward Saturday evening, and we should dry
out after midnight.

As for temperatures, the tight pressure gradient on the front side
of the surface low pressure system will help keep us well mixed
overnight. Dew points will also continue to slowly rise overnight
With a very warm start this evening, readings will not fall off
too much and should range from the upper 40s in the less windy
west to near 60 in the east. The cold front coming in tomorrow
along with clouds and precip will make highs tomorrow quite a bit
cooler than today, in the upper 50s to low 60s. Clearing skies and
decreasing winds Saturday night will allow a drop off to more
seasonal values in the 30s.

.LONG TERM...(Sunday through Friday)
Issued at 319 PM CDT Fri Oct 20 2017

Flow aloft will remain quite progressive.  Upper level ridge over
the northern US Rockies will shift east and flatten. Zonal upper
level jet will be on the north periphery of ridge. Zonal jet will
nose into the area Sun with light precip to occur in the left exit
region. Flat upper trough south of the Aleutians forecast to move
into the Northern Plains Mon and deepen. Showers will continue into
Mon with colder air moving in aloft.

Mon night through Fri...Models were in reasonable agreement at
84 hours. Long wave pattern expected to amplify with long wave
ridges building more so over the western Atlantic and less so over
the eastern Pacific. Long wave trough deepens over central North
America. The GFS was a faster solution than the ECMWF. Both the
ECMWF and the GFS were trending slower with the GFS trending
farther south. Will blend the models.

A cold front will move out of Canada Wed and another on Thu.

Little change to high temperatures for Tue and Wed. Thu highs were
decreased zero to 3 degrees and Fri was decreased four to six
degrees from this mornings package.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1201 PM CDT Fri Oct 20 2017

All sites are VFR and will continue to be so through this
afternoon and tonight. Some MVFR ceilings will move into the KBJI
area late in the period. Breezy south winds with gusts above 20
kts will settle down just a bit tonight, and some LLWS is not out
of the question at some eastern sites. Winds will eventually shift
around to the southwest then west.




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