Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kdlh 240848 

Area forecast discussion
National Weather Service Duluth Minnesota
348 am CDT Wed Jul 24 2019

Short term...(today through thursday)
issued at 337 am CDT Wed Jul 24 2019

One more day of quiet conditions, with mostly sunny skies across the
Northland today. Then, increasing clouds and chances of showers and
thunderstorms return for Thursday, some of which could be strong to

Our overall quiet weather pattern continues today, thanks to a large
area of surface high pressure, currently situated over the western
corn belt states, and upper-level ridging to the west. This high
pressure will gradually sink southeastward today, leading to
pressure falls across the region. There is a small chance for a
shower or thunderstorm over Price County in northern Wisconsin this
afternoon as some very subtle isentropic ascent will be possible in
the low-levels. Modest instability is progged in that area, with
mixed-layer cape values in the 500-1000 j/kg range. Otherwise,
mostly sunny skies today with some diurnal cumulus. Highs in the
lower to middle 80s.

Attention then turns to Thursday for increasing chances of showers
and thunderstorms, especially in the afternoon. The upper-level
ridge will break down overnight tonight, and allow an upper-level
low to translate eastward over the Canadian prairies. Strengthening
flow in the upper-level jet, along with an attendant surface cold
front will sweep into the region Thursday afternoon and continue
into the evening hours. Increased Theta-E advection will lead to
increased mixed-layer instability in the 1000-2000 j/kg range.
Effective bulk shear is a bit on the low side, with values ranging
between 20 to 30 knots per the 24.00z GFS and NAM models, so
favorable updraft organization appears to be an issue. Moreover,
convective inhibition appears to be fairly large, so convective
initiation might not occur until late in the afternoon or evening
hours Thursday. The Storm Prediction Center does have a large
portion of the forecast area in a slight risk for areas along and
west of a line from Sea Gull Lake to Cloquet to McGrath in northeast
Minnesota, with damaging winds and large hail as the main threats.

Long term...(thursday night through tuesday)
issued at 337 am CDT Wed Jul 24 2019

Thursday night and Friday is our next chance for some showers and
thunderstorms. A shortwave moves through the area aloft, which is
accompanied by a surface trough axis. The better dynamics will be
well to the north over Manitoba and Ontario Thursday afternoon and
evening, but we should develop a moderately unstable airmass ahead
of the surface trough with a decent shear profile, so we have a day
2 slight risk of severe thunderstorms. This threat may shift east
into northwest Wisconsin for Friday afternoon and evening, but
the threat may end up being mostly east of the forecast area, and
we would be limited to afternoon diurnally driven convection with
little shear. This will depend on how far east the surface trough
moves and where the upper low is by late afternoon Friday. Friday
will remain hot and humid with highs in the 80s most locations.
Cyclonic upper level flow will shift east of the area on Saturday,
and while the current consensus is for a dry forecast, we may see
some afternoon diurnally driven showers and thunderstorms during
the afternoon and evening hours. Temperatures will remain on the
hot and humid side with highs in the 80s once again nearly

The next strong shortwave is due through the area on Sunday, which
should bring another round of showers and thunderstorms through
during the afternoon and evening. A quieter day may be found on
Monday, but we are getting into a lower confidence time range of the
forecast. For now, some of the models are bringing a fairly strong
shortwave through the area on Tuesday and Wednesday, but the European model (ecmwf)
has US under ridging with drier conditions. For now, have kept to
smaller pops on Tuesday night and Wednesday, and we will have to
see how this all develops. Have kept to near to above normal
temperatures through the forecast.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1232 am CDT Wed Jul 24 2019

Surface high pressure will move off to the east tonight and
Wednesday, allowing for south/southwest winds to develop Wednesday
morning. Scattered to broken cumulus are expected again Wednesday in
most areas, but VFR conditions are expected to prevail. It is not
entirely out of the question that we could see isolated
thunderstorms once again develop during the afternoon tomorrow, but
confidence in anything directly affecting a taf site is very low,
and precludes any specific mention in the official forecast for this


issued at 347 am CDT Wed Jul 24 2019

High pressure over Minnesota today and tonight will keep
conditions fairly quiet over the waters during the next 24 hours.
Winds will generally be light, 5 to 15 knots. On Thursday and
Thursday night, an approaching low pressure system will cause
winds to increase out of the southwest at 10 to 15 knots with
gusts in the 15 to 20 knot range.


Preliminary point temps/pops...
dlh 84 59 83 64 / 10 0 20 60
inl 84 59 84 61 / 10 10 50 40
brd 85 62 84 66 / 10 0 40 50
hyr 84 58 83 64 / 10 0 10 50
asx 86 60 86 66 / 10 0 10 60


Dlh watches/warnings/advisories...


National Weather Service Glossary of Abbreviations