Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 140855

Area Forecast Discussion
National Weather Service Grand Forks ND
355 AM CDT Thu Sep 14 2017

.SHORT TERM...(Today and tonight)
Issued at 331 AM CDT Thu Sep 14 2017

Challenging pop fcst today and tonight. Water vapor shows a decent
short wave over north central SD producing some convection nr the
SD/ND border SSW of Bismarck all night long with expanding area of
light rain northeast of it toward NE ND. Spotty showers on radar
into NE ND. But initially most if not all is drying up in the dry
low levels before reaching the ground. Thus radar vs actual rain
on the ground is deceiving. Very short range CAMs are not handling
situation all that great, but idea is for area of showers to move
ENE into the RRV 12z-18z diminish some as they do. Afternoon will
see some remaining shower chances...but trends are toward low
pops. Now about severe chances. SPC day 1 has Bemidji-Fargo
southeast in marginal risk for t-storms that may form north of a
sfc boundary located at 08z nr PKD-FFM line. This sfc boundary
will drop a bit more south today to nr a Wadena-Wheaton MN line.
This is a bit farther south than was shown yesterday. Idea from
NSSL WRF is for some convection to form north of the boundary in
WC MN (nr DTL-BJI zone) very late aftn/early eve. Shear is
ok...but instabilty and forcing aloft isnt all that great. MUCAPES
from NAM and NSSL WRF show 2500 j/kg but global models are a bit
less. So high uncertainity on strength of any storms that may fire
later today in WC MN. Risk goes into SE ND but CAMs show little
support there.

.LONG TERM...(Friday through Wednesday)
Issued at 331 AM CDT Thu Sep 14 2017

Friday morning should see limited activity before main, stronger
500 mb system moves northeast into the area in the aftn/eve.
Surface low on 00z GFS is farther south than other models and
keeps better instability central/southern MN with a more general
rain in our area. They do agree with track of 500 mb vort in
keeping heaviest stratiform rains over NW 1/2 fcst area where an
inch of rain still likely. GFS seems a bit fast with system
pulling out so will go a bit slower and keep showers into
Saturday...though more scattered. North winds and clouds will keep
temps quite cool with 50s to low 60s for highs.

For Sunday thru Wednesday....
Long wave trough remains over the western US while a long wave
ridge over western Canada gets replaced by a long wave trough.
Long wave trough over the Canadian Maritime will shift a little
east through the period. Long wave ridge over essentially remains
over eastern North America.

The GFS was a faster solution than the ECMWF. The GFS was trending
slightly faster while the ECMWF was trending slower. Prefer the
slower ECMWF solution. Upper level trough moves out of the area Sun

Little change to high temperatures for Sun and Wed. High temps were
increased a degree or two for Mon and increased a degree for Tue
from yesterdays forecast.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 626 PM CDT Wed Sep 13 2017

Still not confident enough to mention vcsh or -ra for any taf
sites over the next 12 hours. BR possible again tomorrow at BJI
around dawn. Light winds and VFR expected for the TAF period.




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