Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1214 PM CDT Friday Jul 25 2014
Short term...(today and tonight)
issued at 330 am CDT Friday Jul 25 2014
Early morning thunderstorms continued to develop across the region
this morning fueled by the veering winds associated with the theta_e
advection in connection with the low level jet. Over the next few
hours this 40kt jet will become more focused across southern...and
eventually southeastern Minnesota. As a result precipitation will continue
to develop for the next few hours...but should gradually wane
shortly after sunset as it enters western WI.
Earlier runs of the rap missed the precipitation that developed in
northeast South Dakota...so it is no surprise that highres models have been
struggling to get a handle on the two areas of precipitation that developed
earlier. As a result most of the runs have been all but discarded.
The 25.06hrrr has finally caught up and it supports the idea of
continued convection this morning...but with a weakening trend after
11z. The severe weather threat is very low given the deep stable
layer beneath the elevated cape...and only marginal 30-35kts of
Looking ahead...skies should clear behind the morning precipitation
yielding another muggy afternoon as dewpoints climb back to near
70f. Increased temperatures slightly across west of i35...and raised
dewpoints as well. Overnight northwesterly winds will push a cold
front through the region sending dewpoints back into the upper 50s
by Saturday morning.
Long term...(saturday through thursday)
issued at 330 am CDT Friday Jul 25 2014
The weekend starts out on a mild note...as the area remains
sandwiched between a southern Continental U.S. Ridge to the south...and a
middle level low to the north in Saskatchewan/Manitoba. The result will
be slightly warmer than normal highs in the middle 80s on
Saturday...followed by increasing precipitation chances into
Sunday as the aforementioned low drops south-southeast from
southern Manitoba. As is common with these types of
lows...precipitation chances appear the highest from central Minnesota
into WI...where forcing/moisture is deeper. Expect showers with
isolated thunderstorms on Sunday...particularly during the afternoon
hours as diurnal heating aids destabilization.
Next week starts out on a dry and mild note as the weekend low
shifts southeast and a broad surface ridge builds across the
central Continental U.S.. the local area remains crammed between western
ridging and eastern troughing at the middle to upper levels of the
atmosphere...yielding cooler than normal highs from Monday through
Wednesday mostly in the 70s...and lows in the 50s.
Thursday and Friday bring the next chance for measurable
precipitation as shortwave energy begins to trickle south on the
western periphery of the eastern Continental U.S. Trough. Chances are not
high at this point given modest forcing and moisture...but
sufficient for the inclusion of 20-30 probability of precipitation.
Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1205 PM CDT Friday Jul 25 2014
Abundant low level mositure ahead of incoming front/trough will
continue broken MVFR ceilings for a couple hours or so. Then VFR over Minnesota
portion of the County Warning Area through the remainder of the period. Some
threat of fog developing ahead of weak boundary if the sky clears
to the east. Will continue to mention that potential at kstc-krnh-
Keau region. Some threat of thunder along boundary as well...but
would be isolated if it did occur. Surface heating limited with clouds to
the east and middle level cap is expected to hold. South/southwest
winds becoming west/northwest with frontal passage...mainly west as front moves
east and weakens.
ceilings expected to lift to VFR through 19z-20z. Then becoming scattered by
evening with some middle/high level clouds into Saturday. Fog
potential will be limited as weak trough expected to move through
this evening. Southwest to west winds expected generally less than
10kts through the period. Some potential of rain showers/thunderstorms and rain into Sat
evening. Will access this for next forecast issuance.
/Outlook for kmsp/
sun...VFR with MVFR/rain showers possible. Winds northwest at 10g15kts.
Monday...VFR. Winds north at 5kts.
Tuesday...VFR. Winds north at 10kts.