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Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
346 am CDT Thursday Apr 24 2014
Short term...(today and tonight)
issued at 345 am CDT Thursday Apr 24 2014
Short term concerns are rain/thunder threat today into tonight and
the chance of wet snow across mainly the extreme northern portion of
the County Warning Area into tonight.
Water vapor imagery showing large area of enhanced clouds with
initial wave lifting northeast into southern Minnesota. Some
lightning associated with this...and based on best lifted indice's...this
should work into south central Minnesota and into a small portion of west
central Wisconsin this morning. Cold temperatures over the northern
periphery of the County Warning Area now...with some middle/upper 30s. As strong lift
moves into the region later this morning...both the NAM and the GFS
indicated a possible rain/snow mix developing over the northern
portion of the County Warning Area. The potwx tool did indicate small areas of
rain/snow into the late morning/afternoon. We did include a slight
chance of snow with the rain over that region into today.
Rainfall amounts of over an inch are possible over the southeast County Warning Area
through the day. This has been well advertised in the grids the
last few days/ the rain area will be affecting the morning commute
over the south east. Second area of thunder possible later this
afternoon over the far northwest County Warning Area. Models were indicating some
MUCAPES of around 500 j/kg by late afternoon as the upper
trough/cold temperatures aloft generate some instability. Mentioned some
isolated thunder over the northwest County Warning Area during the afternoon/early
evening. Afternoon temperatures will once again be held in the 40s
in the areas seeing more widespread rain...mainly eastern County Warning Area.
The upper trough swings east into tonight. Could see a rain
changing to snow scenario over the northeast portion of the County Warning Area
before the precipitation ends overnight. Didnt mention any
accumulation at this time with relatively warm ground.
Long term...(friday through wednesday)
issued at 345 am CDT Thursday Apr 24 2014
The positive note in the long term portion of the forecast is that
models are in better agreement than they were 24 hours ago. The
not-so-positive part is that they have converged on a solution
that features the marrying of the central Continental U.S. Closed low
with a low that back peddles west-southwestward from Quebec. What
this translates to is a prolonged period of temperatures averaging
10 to 15 degrees below normal...and an extended period of 20-30 probability of precipitation
littering the forecast... as the massive low overwhelms the
eastern half of the nation.
In the meantime...the forecast looks on track for moderating
temperatures to near climatological normals on Friday as weak
ridging builds in overhead upstream of the deepening Baja California trough.
Friday highs will range between 55 and 65 degrees across the
majority of the forecast area...with slightly cooler readings in
the lower 50s up toward Ladysmith where residual clouds and
isolated showers will linger.
Saturday will bring a strengthening easterly wind as the
aformentioned trough reaches the plains. Related precipiation
should begin expanding north and east across the area on Saturday
night...with notably increasing rain shower activity on Sunday
afternoon and evening into Monday as a nearly stacked system
meanders across Nebraska and Iowa. Have included 60-80 probability of precipitation across
the bulk of the area during this timeframe...excepting a Little
Falls to Eau Claire line which may be on the northern fringes of
the more organized precipitation. Southern Minnesota locales will have
the opportuninty for thunder...while northern areas /Interstate 94
and north/ may see some snow mix in /primarily in the nocturnal
Wednesday and Thursday feature the previously discussed low probability of precipitation
and cool temperatures...with near to slightly below freezing
readings possibly closing out the month of April.
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1101 PM CDT Wednesday Apr 23 2014
Little to no precipitation currently affecting all weather forecast office mpx terminals at
24/06z initialization time but another round of numerous to
widespread rain is organizing over far southwestern Minnesota and going upstream
from there. This larger area of precipitation will overspread the
coverage area approaching daybreak and persist through midday Thursday.
Short-term models continue to indicate a period of moderate-heavy rain
around daybreak and continuing into early afternoon...which may drop visibility
into IFR rain due to precipitation intensity. As for ceilings...all sites are
VFR but have shown a lowering trend so have delayed the onset of
MVFR ceilings from the 00z set per these trends but am still xpctg
ceilings to drop to MVFR by 09z-10z and remain as such into late afternoon.
Confidence too low at this time to try to pinpoint convection at any of
the terminals despite the presence of marginal instability and an
incoming cold front so have omitted cumulonimbus/ts at this time...although it cannot be
entirely ruled out. Conds improve by late afternoon through the evening hours
tmrw with the frontal passage. Winds to remain NE overnight through much of the
day tmrw then swing around to eventually become west to northwest tmrw evening
with speeds generally 10-15 knots through tmrw afternoon then diminishing.
Kmsp...VFR conds to start then MVFR ceilings likely in the pre-dawn
hours along with another round of fairly solid rain. Rain will
persist through late morning...with a period of moderate-heavy rain likely during
the morning push which may drop conds into IFR range. Precipitation
gradually abates by early-to-mid afternoon and conds improve from
there. Winds to continue from the southeast through late morning...then as a
cold front moves through...wind directions will swing around to SW by middle
afternoon then to west-northwest tmrw afternoon and evening. Speeds will be greatest during
the first 6-9 hours of this taf set...then gradually diminish to
/Outlook for kmsp/
Friday...VFR. West winds 10-15 knots becoming north.
Sat...VFR. NE winds 10-15 knots.
Sun...mainly VFR. MVFR conds possible in -ra. East winds 15-25 knots.