Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
510 PM MDT sun may 19 2013
Short term...this evening through Monday night
issued at 300 PM MDT sun may 19 2013
Large upper low is currently over north central South Dakota. Rain showers are
wrapping around it over the Black Hills into southwestern South Dakota with
another band moving southward from western North Dakota. Surface low
pressure has been stationary just west of abr with strong pressure
gradient behind it.
Upper low will remain over the Dakotas-western Minnesota through
Tuesday morning...and produce widespread rain to the forecast area.
Forecast models show frontogenesis over northwestern South Dakota tonight...moving
into southwestern South Dakota Monday morning. Virtually no instability
indicated... so did not include mention of thunder. Strong Theta-E
advection will be across North Dakota...and models have
drastically cut back quantitative precipitation forecast from last run...with most areas now
showing potential for 0.50 to 1.00 inches of rain. Heaviest rain
will fall over the northern Black Hills as strong northwest
upslope winds will produce high Froude values through midday
Tuesday...with as much as 2 to 3 inches of rain will fall. 850mb
temperatures will cool to around 4c...so some snow is possible
over the highest elevations of the Black Hill...but lead will not
set any snowfall records. The rain that has fallen already has
been soaking into the ground...so additional rain will start
running into streams...but do not expect flooding.
The surface low will wobble around the eastern Dakotas-western
Minnesota...with a strong pressure gradient over western South Dakota
plains. Momentum Transfer shows winds of 30-40 knots on the plains
from Buffalo to Edgemont late tonight through Monday...so issued a Wind
Advisory. Cooler air will move over the forecast area.
&&
Long term...Tuesday through Sunday
issued at 300 PM MDT sun may 19 2013
Showers will remain around the area on Tuesday as upper low is
prognosticated to be somewhere over eastern South Dakota during the day. The highest
chances for rainfall on Tuesday will likely be across the northern
Black Hills...where moist upslope flow will continue...especially in
the morning. Elsewhere...showers should begin to taper off in
intensity...and eventually in coverage as well...Tuesday into
Tuesday night. Medium range models in pretty good agreement with low
finally shifting eastward across the upper Midwest Tuesday night and
Wednesday...with showers generally dissipating from west to east
across the County Warning Area during this time.
Weak ridging behind exiting system will bring mostly dry conditions
later Wednesday into Thursday. A gradual warmup is expected late in
the week...with temperatures back above average levels by the
weekend. Southwest flow aloft will develop again by the end of the
week...so will see chances for showers and thunderstorms increase
Thursday night into next weekend.
&&
Aviation...(for the 00z tafs through 00z Monday evening)
issued at 508 PM MDT sun may 19 2013
Scattered to numerous rain showers will continue into this evening
over much of western South Dakota and northeastern Wyoming...with
widespread MVFR/IFR conditions. A few embedded thunderstorms will
be possible across southern and south central South Dakota through
early evening. Rain showers will continue overnight across the
area...with more widespread steady rain across the northern Black
Hills into portions of northeastern Wyoming and northwestern South
Dakota. Widespread IFR to local LIFR conditions are expected
overnight.
&&
Unr watches/warnings/advisories...
South Dakota...Wind Advisory from midnight tonight to 7 PM MDT Tuesday for
sdz001-002-012-013-026-031-072-073.
Wind Advisory from 6 am Monday to 7 PM MDT Tuesday for sdz030-
041.
Wyoming...none.
&&
$$
Short term...55
long term...15
aviation...10
