Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
548 am CDT Thursday may 23 2013
Short term...(today and tonight)
issued at 415 am CDT Thursday may 23 2013
For the first time in what seems like quite some time we can see
moonlight outside our back door this morning here at the National Weather Service office
in Chanhassen. The surface low that brought 6-7 consecutive days of
measurable rainfall and 4 to 5 inches in many locations across the
forecast area is now over the Great Lakes and we are gaining about 1
mb per hour at the surface early this morning. Northeast flow and
much drier weather is expected today and tonight. The dry and breezy
northeast low level flow today will make it feel even cooler than
the already below normal temperatures in the forecast today. With
little sensible weather to speak of in the short term...one of the
bigger challenges today is to determine just how dry the dewpoints
and humidity will get this afternoon. The saturated ground will
certain aid in providing extra boundary layer moisture.
Nonetheless...mixing down the air between 900-800 mb gives US a very
dry afternoon. The NAM forecast soundings for today suggests we can
mix as high as 830 mb...while the rap...sref...and GFS mix to 850
mb...870 mb...and 875 mb respectively. There should be virtually
cloud free skies today.
The cool and dry day today will set the stage for a chilly night
tonight. No major change to the temperature forecast with lower 40s
west and low to middle 30s east across the forecast area for lows
tonight. The Twin Cities metropolitan should also stay in the lower 40s
tonight. We kept the mention of frost in far eastern Minnesota and west
central WI. In fact...expected temperatures are cold enough in
portions of WI to warrant a frost advisory late tonight.
Long term...(friday through wednesday)
issued at 415 am CDT Thursday may 23 2013
The long term begins with a large high pressure system over the
western Great Lakes region. Much of Friday will be dry...with the
exception of the far west where strong low level Theta-E advection
will commence in the afternoon on the back side of the high. This
coupled with a short wave and middle level frontogenesis moving east
from the northern plains will drive showers and isolated
thunderstorms into the far west by late afternoon...with the
activity passing across the forecast area Friday night and early Saturday.
Elevated instability is minimal Friday night and severe weather is
not expected. The best low level moisture transport is aimed from
the Central Plains into Iowa Friday night with just about all model
solutions pointing to the highest quantitative precipitation forecast staying south of Minnesota.
In the wake of the short wave on Saturday...we are beginning to see
the NAM and sref taking on more of what the European model (ecmwf) has been showing
for 3 days now...and that is a more amplified flow aloft. This is
very evident looking at three runs of the European model (ecmwf) spaced 24 hours
apart. Deeper upper lows along both coast with more ridging in the
center of the country. With time...this builds the surface high
pressure system over the Great Lakes back west across the forecast area along
with drier air. Using the European model (ecmwf) outright would place dry weather
over all but our far western and southern counties in Minnesota for
Sunday and Monday. Going against the grain however are the GFS and
Gem. Both are Adamant on driving wave after wave aloft through the
region both days with convective clusters. Model run quantitative precipitation forecast is in the
several inch range across parts of the Minnesota County Warning Area. On the other hand...
the European model (ecmwf) only has a tenth to a half inch from northeast to
southwest across our area respectively from Friday through
Monday. Hence...the weekend/Holiday may turn out better than the
forecast indicates if the European model (ecmwf) is more correct. Probability of precipitation are more aligned
now with very low chances in WI with higher chances near the
western and southern border.
Although the rain chances are diminishing after Saturday
morning...there is good consensus that abundant low level moisture
will cover the area with a warm front remaining south of US. This
will likely yield plenty of cloud cover with high temperatures
remaining in the 60s Saturday and Sunday with upper 60s to lower
70s on Sunday. Showers and thunderstorms should become more common
over the region from Tuesday Onward as the trough in the west
moves east. This will lift the low pressure system and warm front
into out area. This will also increase our threat for severe
weather.
&&
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 544 am CDT Thursday may 23 2013
No major changes to previous forecast. Winds will remain fairly
steady out of the east-northeast and slowly veer to the southeast
with time tonight.
Kmsp...
VFR expected. Predominantly a northeast wind today.
/Outlook for kmsp/
Friday night...VFR. Chance of showers. Southeast wind 5 to 15 knots.
Saturday...brief MVFR ceilings possible with a chance of
shra/tsra. Southeast wind 10 to 20 knots.
Saturday night...MVFR ceilings and visibilities possible with a
chance of shra/tsra. Southeast wind 10 to 20 knots.
Sunday...MVFR ceilings and visibilities possible with a chance of
shra/tsra...brief IFR conditions possible. Southeast wind 10 to 20
knots.
&&
Mpx watches/warnings/advisories...
Minnesota...none.
WI...frost advisory from midnight tonight to 7 am CDT Friday for
wiz014>016-025-027-028.
&&
$$
Short term...clf
long term...rah
aviation...clf
