Area forecast discussion
National Weather Service Grand Forks ND
637 PM CDT Friday may 24 2013
Update...
issued at 640 PM CDT Friday may 24 2013
The main challenge will be showers and isolated thunderstorms
overnight. Models have been a bit slow with the eastward
progression of highly elevated convection based around 600mb...and
will move this band of showers and storms east a bit quicker.
There is an upstream shortwave entering SC ND at this time...and this
should interact with the current convection and could increase the
coverage some overnight. We will increase probability of precipitation some in the north
into the likely category...with precipitable waters rising over 1 inch.
Otherwise...no major changes planned to this update.
&&
Short term...(this evening through Saturday night)
issued at 330 PM CDT Friday may 24 2013
Forecast challenge for the near term will be ongoing weak
convection moving across southern valley but expanding north.
Overall have liked 12z NAM...however the newer 18z run seems to be
overdoing precipitation across southern Canada.
This evening and tonight...current showers/thunderstorms spreading across
southern valley should depart southeastern zones by middle to late
evening. Storm Prediction Center mesoscale analysis showing most unstable cape axis from
central North Dakota down through the Sioux Falls region...with
most convection initiating just east of axis. Expect this to
dissipate this evening with no redevelopment. A little uncertainty
across northwest...with activity less impressive yet both 18z NAM
and 12z GFS showing a precipitation bulls eye north of border. Will
maintain high chance probability of precipitation for northern valley later into evening
but will not raise probability of precipitation to likely Cat. Should be out of eastern
zones but will keep chance on far southeast for blending purposes.
Saturday and Saturday night...best instability will be in western
part of state. 12z NAM showed positive showalters across our
region throughout day tomorrow...although instability axis will
shift into central Dakotas by early evening. Will keep small swath
of chance probability of precipitation in far west to blend with neighbor...but have
pulled probability of precipitation for majority of County Warning Area due to lack of instability. Highs will
be in middle to upper 60s.
Long term...(sunday through friday)
issued at 330 PM CDT Friday may 24 2013
Sunday and Monday...southwest flow pattern sets up with
shortwave move across North Dakota Sunday afternoon. Will see
increasing probability of precipitation for western two thirds of County Warning Area. Upper ridge moves
into upper Great Lakes by this time and showalters decrease to
below zero across entire County Warning Area by 00z Monday. Very little changes made
to previous forecast with scattered showers/thunderstorms across area on Sun night and Monday.
Beyond Monday...forecast challenges concern mainly temperatures and rain
chances. Active period as middle level SW flow continues through the
period with a series of waves lifting through the forecast area.
Strongest wave looks to be on Thursday although surface and upper
low positions differ between models. Thermal profiles not very
cold but looks to be plenty of cloud cover. Any solar should allow
temperatures to get close to average.
&&
Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 640 PM CDT Friday may 24 2013
There could be a band of MVFR...or perhaps IFR conditions moving
from west to east overnight...with models progging low level
moisture increasing. There is drier air in place along and east of
the Red River valley...so won't mention IFR conditions at all locations
just yet but go into the MVFR category later tonight into Sat
morning. Given the IFR conditions are close to kdvl...will mention
lower ceilings/br here overnight. Expect southeasterly winds to continue
through the period.
&&
Hydrology...
issued at 1244 PM CDT Thursday may 22 2013
River flood warnings remain in effect at Neche along the Pembina
river. Other river flood warnings remain at Pembina...Drayton and
Oslo on the mainstem red...as well as Hallock...Grafton...Dilworth
and Sabin. Sabin will ease below flood stage this afternoon.
The Park River at Grafton has crested and the stage is currently
below 15 feet and continues to fall.
Areal flood warnings remain in effect for Pembina...eastern
Cavalier...and Walsh counties. Water levels across this area should
gradually decrease over the next few days with modest additional
rainfall anticipated.
A Flash Flood Watch remains in effect through Sunday 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. At this
time...officials note the temporary levee on top of the Renwick dam
remains stable and will still be monitored. Otherwise...Lake Renwick
has been slowly receding over the last couple of days.
&&
Fgf watches/warnings/advisories...
ND...Flash Flood Watch through Sunday afternoon for ndz008.
Minnesota...none.
&&
$$
Update...dk
short term...speicher
long term...speicher/voelker
aviation...dk
hydrology...wjb
