Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1247 am CDT Thursday may 28 2015
Short term...(this evening through thursday)
issued at 323 PM CDT Wednesday may 27 2015
There has been a profound lack of cumulus today despite reaching the
convective temperature. Within the last hour...some have begun
forming over Morrison County...with the more developed cumulus across The
Arrowhead into northwest WI and over the Dakotas. A few storms have
developed in the Duluth area...but coverage is far less than hi-res
models have been predicting. The small cluster over the southern tip
of Lake Superior may build southeast into the Hayward and Ladysmith
areas late this afternoon...but there is little confidence for
additional development elsewhere. Maintained slight chance probability of precipitation as
far west as the Mississippi River in case a storm develops from the
cumulus west of Lake Mille lacs...but if this doesn/T take place within
an hour or so we probably could remove probability of precipitation over Minnesota. Any showers and
storms late this afternoon will die quickly around sunset.
Increasing middle and high clouds are expected late tonight as
convective debris drifts east. Low pressure over the northern and
central rockies will propagate across the Dakotas Thursday.
Southerly winds will strengthen and gust to 20-30 miles per hour by afternoon.
Moisture will also increase from west to east through the day...and
may result in a weakly unstable airmass across western Minnesota toward
evening. As the cold front approaches...showers and thunderstorms
will develop there. Moisture will take a bit more time reaching eastern
Minnesota and western WI...so it is probable all of Thursday will be dry with
showers and storms building east Thursday night.
Long term...(thursday night through wednesday)
issued at 323 PM CDT Wednesday may 27 2015
The long term concerns are the severe weather/heavy rain threat
of the passage of the cold front Thursday night into Friday
Severe weather threat lessens into Thursday evening to the west.
Models show decent MUCAPE into the evening but deep layer shear
remains limited generally less than 30kts. This will limit
any widespread activity into mainly the eastern Dakotas into the
evening...and overall intensity trend may decrease as it moves
farther east during the night. The GFS lifts a fairly vigorous
short wave northeast across southeast South Dakota and northwest
Iowa Thursday evening and spreads that into eastern Minnesota by
midnight. Will continue likely pop scenario developing through 06z
Friday. Strong moisture transport associated with this feature as
well...with precipitable water values increase to 1.6 inches over southern Minnesota.
Should see decent rainfall rates with activity as it moves east
with upper flow rather weak. Some 1 inch rainfall amounts
definitely possible again if organized activity does materialize.
The front moves into eastern Minnesota by 18z Friday...with destabilization
through the afternoon. Clouds are expected to limit this
some...but high pop scenario does look good farther east into the
afternoon/evening. Models have trended a bit faster with the
front into Friday evening...with the European model (ecmwf) the slowest. Will trend
probability of precipitation to slight to the far east after 06z Sat.
Cooler and drier conditions still look good for the weekend.
Does look like a warming trend will ensue into early next
week...with readings approaching 80 degree once again by midweek.
Models diverge on overall movement/development of the rain threat
into next week. Will hold any small probability of precipitation to the west and north of
the County Warning Area as warmer air returns. The real rain threat could hold off
until later Wednesday/Wednesday night if the 12z European model (ecmwf) verifies
with 500 mb heights building to 580 decameters.
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1237 am CDT Thursday may 28 2015
Expecting VFR ceilings for the taf period...with the precipitation holding
off until after the period...mainly after 06z Friday. For today
through tonight...expect gradual increase in broad middle and high
level cloudiness...before lower level ceilings spread eastward after
00z tonight. Winds overnight will be light and southerly...but
will increase dramatically during the day...with gusts commonly in
the 25-35 miles per hour range. The gustiness will diminish around sunset as
an inversion develops.
Kmsp...precipitation looks to hold off until after 06z Friday...along
with potential MVFR ceilings. Otherwise wind is the primary focus of
the taf for today...with those strong southerlies expected ahead
of the next weather system.
/Outlook for kmsp/
Friday...MVFR/IFR ceilings/visibilities in shra/tsra. Winds SW 5-10 kts becoming
north-northwest at 10-20 kts.
Sat...VFR. Winds NE 10 kts.
Sun...VFR. Winds southeast 10 knots.