Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
320 PM CDT Wednesday may 6 2015
Short term...(this evening through Thursday night)
issued at 319 PM CDT Wednesday may 6 2015
A broad area of low pressure extended from the southeast
sk/southwest mb area into northwest Kansas this afternoon. Low
pressure will move into the eastern Dakotas tonight...then into
Minnesota on Thursday and drag a cold front through the region
into Friday. Few echoes were occurring as of 20z over our
County Warning Area...with a line of showers and storms from western Minnesota
into southeast Iowa with more showers over northwest Minnesota.
Moisture will continue to increase tonight and precipitable water values are
expected to rise 1 to 1.3 inches by 12z...and remain that high
through Thursday. Precipitable water values are expected to be around 1.2
inches at inl around 12z...that puts them near the highs for this
time of year. A southerly low level jet...with 850mb winds from 40 to 50 kts
will develop across the region tonight. The axis of strongest
moisture transport will nose into southern parts of Northland
around 12z...then continue north through the day gradually
shifting into our eastern County Warning Area in the afternoon then moving east
late Thursday night. Showers will becoming increasingly more
likely late tonight into Thursday from west to east. We kept a
mention of thunderstorms tonight into Thursday morning...but
coverage may be limited until Thursday afternoon when better
instability develops. Showers and storms will gradually diminish from
west to east Thursday night as the better forcing and the low
level jet shift east.
In addition to the shower threat...fog may develop late tonight
and last into at least Thursday morning. Areas around Lake
Superior will have the best chance at seeing some fog.
Long term...(friday through wednesday)
issued at 319 PM CDT Wednesday may 6 2015
There could be lingering light rain showers over the Northland
Friday morning in the wake of the cold front that will have passed
through the region Thursday night and early Friday. High pressure in
Canada will build into the region...providing cooler and drier
weather for Friday afternoon through Saturday.
An upper level low will cross through the American southwest Friday
and Saturday and lift into the plains Saturday night and Sunday. It
will become a stacked low pressure system by Sunday once it meets
its surface reflection in the Central Plains. This stacked low will
lift NE into the Iowa/MN/WI region Sunday night and Monday. The
GFS/ECMWF/Gem models have some noticeable differences in the track
of the low...but are still indicating the potential for the
Northland to get rainfall Sunday night through Monday night as the
low moves through the region. The GFS and Gem have similar low
tracks...from northwest Iowa to just north of Green Bay. The European model (ecmwf) is a
little farther south. Leaned on a blend of the three models. The
northern forecast area will likely have the lowest chances of
getting rainfall because of the dry NE flow from Ontario which may
shunt the showers farther to the south. Temperatures will be cool
Sunday and Monday.
The European model (ecmwf) and GFS indicate surface high pressure will move back into
the Northland during the Tuesday and Wednesday timeframe.
Temperatures will should trend back to near normal by Wednesday.
There could also be an upper level low over Ontario at this time.
The cooler air aloft means late morning and afternoon scattered
cumulus clouds are likely Tuesday and Wednesday...so avoided
forecasting sunny skies.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1252 PM CDT Wednesday may 6 2015
Much of NE Minnesota and northwest Wisconsin had IFR/MVFR broken/overcast ceilings
early this afternoon. Delayed the timing with which these low
clouds will lift and scatter out back to VFR to the middle of the
afternoon for most terminals. Think the threat from the morning
showers and storms. However...a stronger low level jet of 35 to 45
knots around 1500 feet will develop tonight and likely bring more
showers and storms through the region from south to north. The
confidence of storms affecting any particular terminal is low...so
left -tsra out of the forecasts at this time. The strong low level
jet will cause significant low level wind shear through Thursday morning.
Lowered the ceilings to IFR/MVFR later tonight and early Thursday. The
models are indicating much of the region will likely get socked in
by low cloud cover...drizzle/showers...and lower visibility. The
IFR/MVFR conditions could linger well into Thursday morning or
even Thursday afternoon.
Preliminary point temps/pops...
dlh 51 70 47 58 / 60 80 80 20
inl 56 70 41 53 / 60 70 60 20
brd 59 72 45 57 / 70 80 70 10
hyr 60 76 55 63 / 50 80 80 30
asx 53 79 54 62 / 30 70 70 30
Ls...Small Craft Advisory until 10 PM CDT this evening for lsz143>146.