Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Duluth Minnesota
329 am CDT Tuesday Oct 21 2014
Short term...(today through wednesday)
issued at 328 am CDT Tuesday Oct 21 2014
Forecast focus in the near term will again revolve around cloud
cover...then emphasis shifts to rain chances on Wednesday.
08z surface analysis showed high pressure centered over far
northwest Ontario with ridging extending southwest into
Minnesota/Wisconsin. A stratus deck with bases from around 1500ft
to 2500ft covered much of the Northland...with the southwest
quarter of my County Warning Area mainly cloud free. Cloud free areas will see
some patchy fog through about 9 am. The 00z kinl sounding showed the
moisture was rather shallow. These clouds for the most part have
not made much westward progress so far this morning. They were
continuing to slowly move west across Itasca/Koochiching counties.
There were breaks developing over portions of central WI with
clearing over Eastern Lake Superior. The inversion lowers through
the day today with really dry air above it. Much of the guidance
suggests clearing will occur today...rather quickly through the
morning. However...we will be a bit more pessimistic and hold onto
clouds longer...especially around Lake Superior where an east flow
will delay clearing. The clouds will once again have a big impact
on temperatures and some adjustment will likely need to occur as
the cloud trends become more likely today. We have our warmest
temperatures from the Brainerd lakes to Siren with highs in the upper
fifties. We are coolest in The Arrowhead with highs 45 to 50.
Stronger winds will occur over western areas today as the gradient
starts to tighten there.
We held onto more clouds in The Arrowhead this evening...with
clear to partly cloudy skies elsewhere.
A trough of low pressure will move slowly east on Wednesday as
the high departs. Moisture will be increasing Wednesday with both
the NAM and GFS showing precipitable water values increasing to around an inch
which is quite high for this time of year. Precipitable water values around 1
inch is between 2 and 3 Standard deviations above normal. The
European model (ecmwf) has slowed the onset of precipitation Wednesday...but we followed
closer to the GFS/NAM and bring probability of precipitation further east than the European model (ecmwf)
would suggest. We have the eastward extent of our slight chance
probability of precipitation as far east as the WI/Minnesota border by late Wednesday afternoon.
The higher chances will occur over western areas. The forcing is
not particularly strong during the day Wednesday...but with the
higher moisture moving in we prefer the faster GFS/NAM. There is some
instability present...and although not likely...some thunder could
occur Wednesday afternoon.
Long term...(wednesday night through monday)
issued at 328 am CDT Tuesday Oct 21 2014
An upper low over near the North Dakota and Manitoba border
Wednesday evening will move into northern Minnesota Wednesday night
and Thursday. There will be warm and moist southerly flow ahead of
the approaching trough associated with the upper low. Rain showers
are expected to spread into the Northland Wednesday night and
Thursday ahead of the approaching trough. The models are in much
better agreement than earlier runs...so increased the precipitation chances.
Widespread rainfall of 1 to 2 tenths of an inch are likely.
Warm SW flow will develop Friday. This will likely allow
temperatures to reach the low to middle 60s over much of the
forecast area...which is about 15 to 20 degrees above normal for
this time of the year.
A cold front associated with a central Canadian low will move
through the Northland Friday night. Sunnier and cooler weather is
likely Saturday as high pressure move into the region. Temperatures
will still be about 10 degrees above normal.
The models lose agreement for the late weekend and early next week.
However...both the GFS and European model (ecmwf) indicate a cold front will lift
through the Northland and provide low chances of rainfall.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1226 am CDT Tuesday Oct 21 2014
Discussion...widespread MVFR conditions are in store for the taf
sites throughout the night and into Tuesday morning. Some local fog
in the kbrd area could result in IFR/LIFR cigs/vsbys. Conditions
will improve markedly by late morning Tuesday...with VFR conditions
expected for the afternoon.
Preliminary point temps/pops...
dlh 50 36 54 45 / 10 0 10 70
inl 54 36 58 45 / 0 0 40 70
brd 59 37 58 47 / 0 0 40 70
hyr 53 29 57 44 / 0 0 0 70
asx 50 32 58 43 / 10 0 0 60