Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Grand Forks ND
935 am CDT Monday may 4 2015
issued at 934 am CDT Monday may 4 2015
Made some minor changes to cloud cover across the southern forecast area
otherwise forecast unchanged.
Update issued at 645 am CDT Monday may 4 2015
Temperatures have fallen a bit more than expected this morning in the
northwestern counties...but think they should recover quickly with
sunshine already. Did include a patchy frost mention a bit further
south and east than the advisory.
Short term...(today through tuesday)
issued at 401 am CDT Monday may 4 2015
Temperatures will be the main issue for the short term.
Shortwave trough exiting out over Ontario leaves the northern
plains in northwesterly flow aloft that should become more
westerly throughout today. Surface high pressure over the area will
keep winds fairly light today. There will not be much mixing...but
mostly clear skies should allow plenty of sun and think that temperatures
will recover from the upper 30s and low 40s this morning up to
near 70 degrees by afternoon. The surface high will move off towards
the Great Lakes tonight...with low pressure developing over the
northern rockies. Winds will begin to pick up out of the
south...but clear skies should allow temperatures to fall into the 40s
with some 30s in the far east where winds will be lightest.
Tuesday...the upper trough over Colorado begins to lift
northeastward. Southerly winds will continue to pick up as surface low
pressure deepens over Montana. With the system well to the south we
should stay dry throughout the day...but some increase in cloud
cover is possible over the southern counties. Highs should be a
few degrees warmer than Monday with better mixing...topping out
mainly in the 70s.
Long term...(tuesday night through sunday)
issued at 401 am CDT Monday may 4 2015
Tuesday night through Wednesday night...the upper trough begins to
lift from The Rockies into the Western Plains...moving into the
Dakotas by Wednesday night. The models are in fairly good
agreement on bringing the warm front into the County Warning Area Tuesday night.
Given recent dry air think saturation may take a while so
continued to hold off on likely probability of precipitation until after midnight. Precipitation
should continue into Wednesday as the surface trough enters the
western Dakotas. The models begin to show some differences in the
placement of the surface low by Wednesday night...with the European model (ecmwf) and
Gem further north than the domestic models. Still some uncertainty
as to the exact timing of the different rounds of precipitation and their
placement...but there should be enough large scale forcing and
decent moisture with precipitable waters above 1 inch to go with high probability of precipitation
through Wednesday and Wednesday night. Showalters will be just
below to slightly above zero so just kept an isolated thunder
mention. Clouds and precipitation will keep temperatures from being as high as
they could...but think there should be enough breaks to get into
the 70s. The clouds and precipitation should keep the lows Wednesday
night from falling too much and most places will stay in the 50s.
Thursday through Sunday...a split flow is forecast across North
America with the southern stream over the southern states and the
northern stream over long wave upper level ridge over the West
Coast of Canada moves over the Canadian rockies by the end of the
period and amplifies a bit. Long wave trough over the western US
retrogrades a bit and Delaware amplifies this period.
The European model (ecmwf) was the faster than the GFS throughout the period. The
European model (ecmwf) had a faster solution over the last couple model runs while
the GFS was also faster but to a lesser degree.
Little change to temperatures for Thursday and Friday. Zero to four degrees lower
for Sat ad a couple degree lower for sun compared to yesterdays
Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 645 am CDT Monday may 4 2015
VFR conditions with only some cirrus clouds. Winds will be light
and variable throughout the period.