Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 201757

Area Forecast Discussion
National Weather Service Grand Forks ND
1257 PM CDT Sat May 20 2017

Issued at 1255 PM CDT Sat May 20 2017

Tweeking rain advance timing in grids...but so far earlier update
is looking good. Temps falling when rain comes in so did adjust
temps a bit...pretty cool in the rain area with temps nr 40.


.SHORT TERM...(Today and tonight)
Issued at 337 AM CDT Sat May 20 2017

Challenge today will be timing of northward moving rain band and
its thicker clouds and impacts on temps. Should see a wide temperature
gradient across the area with 40s under the clouds and rain in the
far south and 60s in the north where the drier air will persist
and allows more solar. Band of rain eventually makes its way into
the central valley this afternoon and possibly into the northern
valley by evening. Expecting a quarter to half inch in the valley
and to the east with the higher amounts in the MN half of the FA.
Across the DVL basin rainfall is less certain with a few
hundredths to a tenth or so possible.

Tonight light precipitation will continue to be possible across
the entire area. There seems to be a low possibility of few snow
showers if and where enough dynamic cooling occurs as hires models
showing a near SFC layer that is cool enough to support snow.
Occurrence of any snow would be mostly confined to higher terrain
areas verses the RRV. Again the possibility is low but will need
to be monitored.

.LONG TERM...(Sunday through Friday)
Issued at 337 AM CDT Sat May 20 2017

Sunday will continue the light rain likelihood as the center of
the broad 500mb low remains overhead. Widespread rain area will
lift to the northeast with more scattered light rain possible
again Monday as 500mb vorticity drops south over the area on the
backside of the counter clockwise upper level low. A cool thermal
profile with 925mb temps in the 0 to 10C range Sunday and Monday.
Given the cool temps any break in clouds will quickly fill back
in. Highs in the 50s are expected with a few low 60s by Monday if
the system exits as expected.

Upper air pattern remains fairly progressive through the period.
Split flow is to remain across North America with the northern
stream over southern Canada/northern states and southern stream
forecast to be over the southern states. Long wave ridge remains
over western North America. Long wave trough over the Northern
Plains shifts into eastern North America by the end of the period.
The long wave ridge weakens while the long wave trough strengthens.

The ECMWF was trending slower while the GFS was trending faster. The
GFS was the faster solution. Will blend the models. Upper level
ridge moves through the area Wed.

High temperatures were increased zero to three degrees for Tue and
zero to two degrees for Wed. High temps were decreased one or two
degrees for Thu and decreased one to four degrees for Fri from
yesterdays forecast package.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1255 PM CDT Sat May 20 2017

For aviation interests...will watch advance of moisture
northward...and the resultant lowering of the cloud bases from VFR
early this aftn then eventually turning MVFR to in some cases
IFR...esp east of the RRV. East-northeast winds will continue 10
to 20 kts.




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