Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Twin Cities/Chanhassen Minnesota
656 PM CDT Sat Jun 24 2017
Short term...(this evening through sunday)
issued at 330 PM CDT Sat Jun 24 2017
A very potent short wave for late June was rotating southeast
across east central Minnesota this afternoon. This short wave and
associated instability, was enough to generate a few storms in
central/southern Minnesota during the early afternoon. Some of the
stronger storms, although weak considering late June, produced up
to half inch hail due to freezing levels of 5-7k. Some of the
hail accumulated as noted on social media reports. As daytime
heating abates, most of the storms will turn into light showers
and end toward sunset. Upstream observations in northwest
Minnesota had low clouds, and even some light showers that was
associated with a secondary wave moving southward. This wave could
also generate a few showers in central/east central Minnesota
after midnight, but a cool northwest wind and temperatures in the
upper 40s/lower 50s will may it feel like early-middle may.
Sunday will be drier than today, especially in western Minnesota
where temperatures will likely rise to near 70. In eastern
Minnesota, and west central Wisconsin, the remnants of the upper
low moving slowly eastward over the Great Lakes, will continue to
generate a few afternoon/early evening showers/storms Sunday.
Where the showers will be more persistent, highs will only be in
the low to mid 60s.
Long term...(sunday night through saturday)
issued at 315 PM CDT Sat Jun 24 2017
The main concern in the long term period is the Tuesday night
through Wednesday period as thunderstorms will be likely across the
region with the potential for severe weather and heavy rainfall.
Starting out with Sunday night, we will be enveloped in deep
cyclonic flow still but surface high pressure will be sinking in
from our northwest. Expect that by tomorrow evening, any showers in
western WI/eastern Minnesota will quickly dissipate. The remainder of the
area will stay dry. With the cool airmass in place and clearing
skies overnight, expect lows to drop into the 40s area-wide, except
the inner Metro may stay in the low 50s. The western Continental U.S. Upper
ridge will make eastward progress Monday, pushing the eastern Continental U.S.
Trough eastward and introducing anti-cyclonic low level flow to our
area. The surface high will drop into western Minnesota by Monday
afternoon, so we'll get a break from the breezy couple days we've
seen. With light northerly flow, highs will top out in the low 70s,
but with lighter winds and sunny skies, it will feel quite a bit
warmer than the previous few days.
The high will quickly push east of US and introduce southerly flow by
Tuesday morning. Southerly winds will increase through the day,
especially in western Minnesota where the pressure gradient becomes tighter
as surface low pressure develops across the western Dakotas. Strong
warm air and moisture advection will build across the Dakotas as
will instability. The arrival of a decent shortwave riding over the
top of the ridge will set off thunderstorms in the Dakotas. The Storm Prediction Center
has highlighted this area in a day 4 outlook and clips far western
Minnesota. For US though, the timing of the wave would be late Tuesday
night. Most of the forecast area has likely pops for Tuesday night
as storms roll in from the Dakotas, but would likely be elevated and
not as strong by the time they reach our area. For eastern Minnesota and
western WI, the best chance of storms may be close to daybreak on
Wednesday. The main cool front associated with the surface low
looks to come through Wednesday afternoon and evening, but there may
too much rain and cloud cover Wednesday morning into the afternoon
from the Tuesday night activity to allow for significant
destabilization. It does still bare monitoring through as this is
still 4 days away and timing could easily change.
The pattern remains active toward the end of the week as more
shortwave energy is pushed out ahead of a parent longwave trough
over the northern High Plains. More showers and thunderstorms are
possible Friday into Saturday. Cool temperatures might be shaping
up for next weekend as well as the guidance wants to bring the upper
longwave trough overhead by Saturday.
Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 656 PM CDT Sat Jun 24 2017
MVFR cigs will build southeast from northwest Minnesota this
evening, reaching most of the taf sites tonight. Cigs will lift to
VFR Sunday morning. It appears only rwf may remain southwest of
the MVFR cigs. Gusty winds again Sunday, with some to 25-30 kts.
Kmsp...MVFR cigs are still expected to arrive around 09z and lift
quickly mid morning Sunday.
/Outlook for kmsp/
Mon...VFR. Winds northwest 5-10 kts.
Tue...VFR. Rain showers/thunderstorms and rain late, with MVFR cigs. Winds S 5-10 kts.
Wed...VFR/MVFR. Periods of rain showers/thunderstorms and rain early. Winds south-southwest 10-15 bcmg west.