Area forecast discussion
National Weather Service Grand Forks ND
1141 PM CDT Monday Jun 17 2013
Update...
issued at 1140 PM CDT Monday Jun 17 2013
Updated for aviation discussion only.
Update issued at 925 PM CDT Monday Jun 17 2013
Current radar showing convection mainly south of I 94 corridor
although we are seeing some new development on the ND side of the
Central Valley. Think with loss of solar any new development will
be short lived and main activity will be across southeastern ND
just ahead of vorticity maximum and in a weakening ribbon of 500 to 1000
j/kg convective available potential energy. Impulse should drop into northeastern South Dakota over next hour
and expect end of activity by 04z. Will go ahead and adjust probability of precipitation
for this. Dewpoints in the northeast now into the upper 40s so
have lowered temperatures a few degree in this area...but do not see the
drier low 40s/upper 30s over southwestern Ontario impacting my
northeastern zones so will keep lows in this region in the 45 to
50 range. Needed to raise hourly temperatures across southern valley for
the next three to four hours...but temperatures elsewhere look good.
Other than minor cloud trend changes...not other changes expected
with this update.
Update issued at 633 PM CDT Monday Jun 17 2013
Moderate cape in western zones...and southeastward movement of
h500 low will keep some rain showers and an isolated thunderstorms across
my southwest through middle evening. Do have a couple of thunderstorms on
radar at current time...one over western Cass County and the other
in central Polk. Convection should dissipate over next couple of
hours but showers could hold on in the Valley City area as upper
low approaches...but think all activity will end by midnight. Will
fine tune probability of precipitation for 7 PM CDT update with no sig changes to temperatures.
&&
Short term...(this evening through Tuesday night)
issued at 310 PM CDT Monday Jun 17 2013
Concerns for the short-term forecast include dissipating showers/
T-storms this evening and temperatures overnight. Although there
exist model variances with quantitative precipitation forecast output...synoptic features are in
good agreement and will use a blended solution.
20 UTC radar shows a scattered line of showers from near Cando to
Park Rapids. Expect this activity to sag southward late this
afternoon and evening as a weak upper low moves into west central
Minnesota by 06 UTC tonight. A lightning strike or two is possible...but
overall vertical extent of cumulus is limited...so not expecting much
in the way of thunderstorms. Majority of cumulus/showers will dissipate
after sunset with surface high pressure building from the west.
Winds will become light and variable by daybreak Tuesday morning
and with mostly clear skies...nighttime lows will drop into the
upper 40s to middle 50s.
Tuesday will be mostly sunny and dry as the surface high pressure
drifts into central WI. Southerly return flow will develop in its
wake...resulting in light southerly surface wind from 5 to 10 miles per hour.
Soundings show the boundary layer warms 1 to 4 c by Tuesday
afternoon so expect highs in the middle to upper 70s.
Long term...(wednesday through monday)
issued at 310 PM CDT Monday Jun 17 2013
A short-wave ridge aloft will move across the northern plains
Wednesday and Thursday. Greatest instability and forcing for
Wednesday is west of the forecast area...but will keep low-end
chance probability of precipitation going due to weak middle-level warm air advection/
isentropic lift and the possibility of a rogue short-wave ripple
moving through the ridge axis. Shower and thunderstorm chances
increase Thursday as flow aloft shifts to the southwest and the
primary instability axis moves into the central/eastern Dakotas.
With additional low-middle level warming...temperatures will reach
into the lower 80s most places both days with morning lows from
the upper 50s into the 60s.
Thursday night through Monday...active convective pattern setting up for
the long range period. Upper low over Pacific northwest to remain fairly
stationary until the weekend when it begins to propagate east.
This will keep forecast area in an extended period of SW middle level flow. With
persistent southerly flow will see significant moisture flux into
forecast area resulting in increasing precipitable water values and dewpoints
climbing into the 60s most areas. As a result there will be plenty
of instability and cape available. Main question will be where low
level boundaries/low level forcing sets up as broad area of low
pressure will affect the forecast area through the period. Models close with
main features however differ on location of low level boundaries.
For this tough to Pin Point where favored areas for convection
will be. Probably be seeing quite a bit of cloud cover through the
period with temperatures close to seasonal averages and mild
overnight minimums.
&&
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1140 PM CDT Monday Jun 17 2013
VFR conds tonight and tomorrow. Middle level ceilings associated with
dissipating showers west of far will erode by 06z. Should see
decreasing clouds overnight with winds shifting to the southeast.
Light southerly flow drg the day Wednesday with potential for some VFR
ceilings dropping into northestern ND tomorrow afternoon...but will likely remain
north of dvl-gfk-tvf area.
&&
Fgf watches/warnings/advisories...
ND...none.
Minnesota...none.
&&
$$
Update...speicher
short term...Rogers
long term...Rogers/voelker
aviation...speicher
