Area forecast discussion
National Weather Service Bismarck ND
331 PM CDT sun may 19 2013
Short term...(this evening through monday)
issued at 330 PM CDT sun may 19 2013
The highlight of the short term is the continued heavy rainfall
and flooding threat across western and central North Dakota
through Monday night and a Flood Watch remains in effect.
Overall...the deterministic guidance is in good agreement on
retrograding the deep surface low currently across northeast South
Dakota west through tonight...before propagating again east on
Monday. Given the good agreement...followed a blend of the 12 UTC
GFS/Gem/ECMWF and 15 UTC sref for all fields. This places the
low level deformation zone and associated moderate to heavy
rainfall generally across the Highway 85 corridor and into the
north central through tonight. Will continue to monitor the James
River Valley late this afternoon through early evening as breaks
in the cloud cover is allowing some surface based destabilization
to occur. Being so close to the surface low...deep layer shear is
marginal for this part of the County Warning Area...however...it would be favored
for a possible weak spin- up tornado/land spout with the low level
vorticity should sufficient near surface destabilization occur.
Also for tonight...did issue Wind Advisory for western and north
central North Dakota from 00 UTC to 15 UTC Monday. NAM/GFS bufr
soundings indicate 40-45 kts to mix in the 900-875 mb layer as the
pressure gradient strengths with the retrograding surface low.
For tomorrow...as energy currently across Nebraska pivots around
the main upper level low into North Dakota...moderate to heavy
rain will once again become widespread across all of western and
central North Dakota. By Tuesday morning...an additional two to
three inches of rainfall is possible for much of the area. See the
hydrology discussion below for details.
Long term...(monday night through sunday)
issued at 330 PM CDT sun may 19 2013
The main forecast issue through the long term period is continued
heavy rain and potential for flooding. The latest suite of 19/12z
models is in very good agreement regarding the track of the closed
upper low through the region. The upper low Monday night is forecast
to be over the eastern Dakotas/western Minnesota border...and move
southeastward gradually to southern Minnesota by daybreak Wednesday
morning...then move eastward into the Ohio Valley as another upper
level low makes its way into the West Coast. This consensus
indicates a prolonged period of moderate to heavy rain continuing
Monday night into Tuesday...impacting most if not all of western and
central North Dakota. Showers are expected to become more scattered
Tuesday night into Wednesday. Rainfall amounts in the 24-hour period
from Monday night through Tuesday night are expected to range from
around 1/3 to 2/3 of an inch over a large area of western and
central North Dakota. This in addition to what has already been
received through this weekend...and what is forecast for Sunday
night and Monday...will keep flooding issues the main threat across
the region. In addition to flooding concerns along small
streams...and low lying areas...will be monitoring rivers closely
this week...especially the faster responding points such as Apple
Creek near Menoken.
In addition to the rains...gusty winds are expected to continue
Monday night through Tuesday night...as the intense upper level low
is stacked over the surface low...and northerly winds from the
surface through h700 remain unidirectional from the north. Expecting
20 to 30 miles per hour sustained winds with gusts to near 35 miles per hour at times.
Upper level ridging will become established over the region
beginning Wednesday afternoon...ahead of the next large low pressure
system over the West Coast/rockies. This system is expected to
remain over The Rockies and begin to set up a southwesterly flow
aloft over the northern plains by Friday.
The next best chance of rain showers and thunderstorms is
Friday...and continuing through the weekend.
Expect cool weather conditions Tuesday with highs in the
50s...warming gradually to the upper 60s and 70s by Saturday.
&&
Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 330 PM CDT sun may 19 2013
Slow moving low pressure over northeast South Dakota will impact
the area with stratus...fog...rain and thunderstorms through the
18 UTC taf cycle. MVFR to IFR conditions in moderate rain and
stratus for kbis...kmot and kdik. For kjms...scattered showers and
thunderstorms re-developing this afternoon and evening with IFR
conditions in stratus possible. For kisn...becoming MVFR in rain
and stratus this afternoon. Northerly winds gusts of 30-35 kts
possible at kdik...kmot and kisn late this afternoon through
tonight.
&&
Hydrology...
issued at 330 PM CDT sun may 19 2013
A Flood Watch remains in effect for all of western and central
North Dakota through Monday night. Did issue a Flood Warning for
the Pipestem creek near Pingree as minor flooding is expected by
Monday night...with moderate flooding expected by Wednesday. The
James River near Grace City may rise to minor flood stage by
Wednesday. The Apple Creek near Menoken may make an in bank rise
to just shy of flood stage by Monday evening. The Beaver Creek
near Linton and the Cannonball river at Breien may rise to minor
flood stage by Wednesday. The little Muddy river near Williston may
rise to minor flood stage by Monday night. All these forecasts are
highly dependent on how much rain falls over the next 36 hours.
Will also have to monitor for overland flooding.
&&
Bis watches/warnings/advisories...
Flood Watch through Tuesday morning for ndz001>005-009>013-
017>023-025-031>037-040>048-050-051.
Wind Advisory from 7 PM CDT /6 PM MDT/ this evening to 10 am CDT
/9 am MDT/ Monday for ndz001>004-009>011-017-018-031>033-040-043.
&&
$$
Short term...ayd
long term...jv
aviation...ayd
hydrology...ayd
