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Area forecast discussion 
National Weather Service Grand Forks ND
1252 PM CDT Thursday Aug 21 2014

issued at 1249 PM CDT Thursday Aug 21 2014

No update necessary.

Update issued at 925 am CDT Thursday Aug 21 2014

Lead short wave has pushed east of the forecast area so trimmed back on probability of precipitation
across west central Minnesota. Secondary wave lifting through north
central/NE ND and associated surface boundary and low vicinity jms
continues to produce spotty rain showers/isolated thunderstorms and rain across northern tier
of counties of NE ND into northwest Minnesota. With some convergence from modest
low level jet into northwest Minnesota and above features will maintain some
lower end probability of precipitation through the am. Made some pop adjustments in the
near term otherwise no changes to current forecast.

Update issued at 712 am CDT Thursday Aug 21 2014

Water vapor shows the two short waves this moving
through southwestern Minnesota with convective cluster east of it and
one along the Saskatchewan/Manitoba/ND border with continued slow moving
convection moving north-northeast from northwest of Devils Lake
into Manitoba. There has been a tendency for this wave to move
east a bit and convection to develop a bit east over time the last
few hours. For the balance of today...expect the activity over far
southeastern forecast area to move out soon and some lingering
convection in northwest forecast area north of Devils Lake to Langdon area
with spotty activity in between the two through NE ND into northwest Minnesota. As
short waves continue to move east threat for precipitation will diminish
slowly. Tweaked probability of precipitation some mainly to drop some in Bemidji area this
afternoon where had likely probability of precipitation. Went chance probability of precipitation as precipitation potential
doesnt look huge.


Short term...(today through friday)
issued at 325 am CDT Thursday Aug 21 2014

Not unexpected scenario early this morning. One area of
thunderstorms from northern South Dakota/scntrl ND moving east meeting with up
area of storms forming in 850 mb low level jet. Focus of main
rains has shifted a bit south into the Richer 850 Theta-E airmass.
Also got a narrow axis of rainfall more along the upper trough
from north central ND into Manitoba. This is lifting north. In
between from Devils Lake to Hallock south to Grand Forks nothing.
So what happens today past 12z. Not clear cut. Went along with
weather forecast office dlh thinking in that rain showers will continue to expand
northeast and may increase again in coverage this afternoon in far
eastern forecast area as deeper 850 mb moisture moves north ahead of
weak surface low which will move from central South Dakota into southeastern
ND to near Detroit Lakes by 18z. As surface low moves northeast the
rest of the area may well see some scattered precipitation...especially north
and east of surface low. Least chance in SW forecast area.

Main precipitation area lifts northeast out of the forecast area tonight into
Friday. North-northeast winds behind surface low to likely aid in
cooling area down and also considerable cloud cover will not help.
Used superblend for temperatures and seems reasonable with mostly 60s dvl
basin Friday to 70s south and east.

Long term...(friday night through wednesday)
issued at 325 am CDT Thursday Aug 21 2014

After Friday...models diverge with 00z European model (ecmwf) bringing up a low
pressure and considerable rain activity to much of eastern South Dakota into
northern Minnesota later Saturday into Saturday night. GFS/Gem are farther
west with the main rains over western ND into Saskatchewan/western mb. NAM in
between and faster with surface low moving through eastern ND Saturday evening
and heavy rainfall in central ND and less east. For the time being
went along with HPC thoughts which is a wetter one for west-central into
north central Minnesota later Saturday into Sat night.

Sunday-Wednesday...very low confidence through this period with
model solutions diverging early next week. For late
upper shortwave trough will lift out of The Rockies. The position of
the surface low and greatest forcing for precipitation remains uncertain.
Thereafter...the GFS maintains southwest flow aloft with a
progressive upper trough moving across the region for
mid-week...while the European model (ecmwf) is much flatter with the flow. Temperatures are
likely to run primarily below average...but daily temperature trends will
hinge on how exactly the pattern resolves its self


Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1249 PM CDT Thursday Aug 21 2014

Pattern resembles more of a late fall regime with persistent lowered
ceilings and visibility. Surface analysis shows low pressure located over eastern ND
with abundant low level moisture present. Observation show widespread MVFR
ceilings...with spots with scattered cloud cover. Expecting some solar to
penetrate during the afternoon hours raising ceilings a bit...but 925mb
and 850mb forecast moisture fields indicate that ceilings will be
persistent through the taf period. Therefore...raised ceilings a bit for
the first part of the period toward VFR criteria. However...loss of
heating after sunset will allow ceilings to fill in...and will drop down
to the MVFR/IFR category again. Some areas of patchy fog can be
expected...but not looking to be predominant at the taf sites at this time.


Fgf watches/warnings/advisories...


short term...Riddle
long term...makowski/Riddle

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