Area forecast discussion
National Weather Service Grand Forks ND
959 PM CDT Wednesday may 22 2013
Update...
issued at 959 PM CDT Wednesday may 22 2013
fog loop/surface observation indicated forecast area was mostly clear.
Patchy middle clouds were over Becker, Otter Tail and Hubbard counties.
Another patch was west of the Red River in northeast ND. Thin cirrus
was moving in from the west. Middle clouds were moving southwest 25 to
30 knots.
Surface high pressure was located from central Canada into central
ND and will continue to build into the area overnight. No change to
low temperature from previous discussion.
Update issued at 659 PM CDT Wednesday may 22 2013
Upper level low that has plagued the area the last few days was
located over the eastern Minnesota/Iowa border. Upper low forecast to move
east. Another upper level trough was over western Ontario and
extended into Hudson Bay. Some drying/darkening was noted on the
water vapor loop over the area. Also weak cold front was located
over the northern valley. Surface winds still gusting Post frontal.
Tweaked low for tonight...a degree or so lower east and a degree oe
two higher elsewhere.
&&
Short term...(this evening through Thursday night)
issued at 332 PM CDT Wednesday may 22 2013
With no additional rainfall expected through Thursday...primary
forecast challenge will be temperatures. GFS/NAM/ECMWF/Gem are in
good agreement and will use a blended solution.
20 UTC satellite imagery shows low stratus/stratocu along and
south of a line from Lisbon to Park Rapids. Skies will become
mostly clear overnight as surface high pressure builds across the
region...allowing temperatures to drop into the upper 30s to low
40s. With clear skies and some low-level cold air advection across
northwest and north central Minnesota overnight...will need to watch how
low into the 30s temperatures drop. Current dew points across
northwest Minnesota are as low as 34 degrees...so Don/T think air
temperatures will fall much further.
Thursday will be sunny and dry with the surface ridge axis along
the valley floor by 18 UTC. Boundary layer temperatures will be
near or a few degrees cooler than today...so despite abundant
sunshine...expect daytime highs only in the 60s. Mostly clear
skies will continue Thursday night with temperatures similar to
tonight...from the upper 30s to middle 40s.
Long term...(friday through wednesday)
issued at 332 PM CDT Wednesday may 22 2013
Precipitation chances increase Friday afternoon and evening from
the west as a middle-level warm front begins to slide across the
Dakotas. Isentropic lift along the 300 k surface and precipitable
water near one inch will result in some showers and perhaps a few
thunderstorms. Not much upper level support and most instability
remains across the western Dakotas into eastern Montana...but will
maintain isolated thunder mention. Still some precipitation
coverage and timing uncertainty...so will keep probability of precipitation in the high
chance category...likely to be raised to 60 percent or higher
when better confidence is achieved.
Some lingering showers and thunderstorms will continue into
Saturday...but does not appear at this time to be an all day wash
out. Despite warm air advection aloft...the boundary layer remains
cool with surface temperatures Friday and especially Saturday
below seasonal normals with highs in the 60s and lows in the 40s
to lower 50s.
Forecast challenge Saturday night through Wednesday will be rain shower/T
chances. Models in reasonable agreement through the long range.
Middle level ridge axis to gradually shift east putting forecast area in
increasing SW flow aloft by first half of next week. For most of
the weekend low level forcing and moisture axis remains across
western and central ND so question will be how far east convection
gets after diurnal initiation. Better chances for precipitation next week
as low pressure and above forcing and moisture gradually shifts
east. Temperatures likely to hold at or a little below average
through the Holiday weekend then moderating to at or above average
to start work week.
&&
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 659 PM CDT Wednesday may 22 2013
Visible loop indicated scattered to broken cloud deck over the northern half
of the forecast area and was moving to the south at about 20 knots.
Also weak cold front was moving through the area. So will keep winds
up for the next couple hours. Otherwise a clear sky is expected over
night and winds will subside.
&&
Hydrology...
issued at 959 PM CDT Wednesday may 22 2013
River flood warnings remain in effect at Walhalla and Neche along
the Pembina river...with Walhalla having crested and falling...and
Neche now cresting.
The Park River at Grafton is expected to crest near the record of
16.5 feet tonight or Thursday morning.
There are also a few river points within the area that are expected
to reach minor flood stage.
Areal flood warnings remain in effect for Pembina...eastern
Cavalier...and Walsh counties. The main surge of water is now into
central Pembina and Walsh counties...and will continue to move
toward the Red River. Water levels across this area should gradually
decrease over the next few days with little additional rainfall
anticipated.
A Flash Flood Watch remains in effect through Friday afternoon for
areas downstream of the Renwick dam on The Tongue river. Water
remains very high at the dam site and is being held back by a
constructed earthen levee on top of the dam structure. Also...
officials are continuing to monitor several retention dams to the
west of Renwick dam. At this time...officials note the temporary
levee on top of the Renwick dam appears to be stable and will be
continually monitored. Lake Renwick has slowly receded over the past
few hours. Water has stopped flowing over the emergency spillways at
most of the retention dams west of the Renwick dam. However...the
threat remains and failure would mean major flooding would be
imminent for the cities of Akra...Cavalier...and Bathgate.
&&
Fgf watches/warnings/advisories...
ND...Flash Flood Watch through Friday afternoon for ndz008.
Minnesota...none.
&&
$$
Update...hoppes
short term...Rogers
long term...Rogers/voelker
aviation...hoppes
hydrology...tg
