Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Duluth Minnesota
337 am CDT Friday Aug 22 2014

Synopsis...
issued at 308 am CDT Friday Aug 22 2014

Middle level ridging continues over the County Warning Area early this morning as a
broad area of weak low pressure shifts slow east underneath.
Latest RUC shows a 925 low over wctrl wisc with an inverted shear
axis extending northwest towards kbji and krox. This is followed
by a cold front stretching from eastern Manitoba south to central
sodak. Main story over County Warning Area this morning is trapped moist layer...
about 5k feet in depth...underneath subsidence inversion. Br/fog and
even some drizzle is occurring in many areas. A few convective
cells have tried to develop over southeastern wisc zones in an area of low
level thetae ridge axis. Limited instability has allowed fairly
short temporal nature to development.

&&

Short term...(today through saturday)
issued at 308 am CDT Friday Aug 22 2014

Today...forecast model soundings suggest it may take quite some time to
dissipate the canopy of stratus and br across the region. Conditions
pressure deficits show a trend to diminishing br by 14/15z....then a
relatively saturated cloud layer finally breaking after 2pm.
Precipitation chance seems quite limited by ridging aloft and lack of low
level focus for convergence. The greatest opportunity may arise in
the afternoon ahead of approaching frontal boundary pushing towards
northwestern County Warning Area. Middle level warmth will limit much development until
afternoon as 70h thermal cooling commences over western County Warning Area.

Tonight...middle level ridge amplifies overhead tonight in response to
upstream strengthening of trough over rockies. Frontal boundary will
stall north and west of County Warning Area however its associated prefrontal
thetae ridge will be nearby. Although the dry forecast was carried
over from previous forecaster...will need to watch for some development
of convection making it into northwestern County Warning Area tonight.

Tomorrow...height falls move into western High Plains with surface low
organizing over sodak. A southwesterly middle level flow will begin over the
County Warning Area as the ridge axis shifts east. Surface high pressure will increase
over Lake Superior with distinct onshore component to boundary layer
wind. Tough forecast for precipitation as main focus appears to be shaping up
over the western County Warning Area by late in the day. Clouds/precipitation forecast for North
Shore based on a combination of terrain lift and a gradual
deepening of synoptic scale moist layer.



Long term...(saturday through thursday)
issued at 308 am CDT Friday Aug 22 2014

The strong surface low will move north along the western Minnesota
border Saturday night and Sunday morning...bringing another round of
showers and thunderstorms...mainly the the western portions of the
forecast area overnight. Have gone ahead an increased probability of precipitation to
categorical there...with high end chance to likely probability of precipitation elsewhere as
the warm front moves north across the region. Models are getting
close enough together to have a fairly high confidence...though the
track is still somewhat problematic. With the surface low moving
northeast of the region Sunday and Sunday night....a cold front is
dragged through the area. Depending on the model...the timing
differs...but either way we are looking at more chance to likely
probability of precipitation. The European model (ecmwf)...which is farther west than the GFS implies we may
have some potential for severe storms...as the front comes through
later and allows for heating during the day to build instability
ahead of it. Will have to watch this carefully in the next few
days. Have gone with some fairly warm high temperatures on Sunday...but if
the European model (ecmwf) works out...these will need to be raised. This storm
lingers over western Ontario for Monday before moving off to the
northeast Monday afternoon and night...keeping some chance probability of precipitation
going over the area both periods with cooler temperatures.

Our next significant storm system comes by on Tuesday through
Wednesday. Models are varying significantly by this point...with
the the GFS bringing an area of moderate to heavy rain across the
forecast area...and the European model (ecmwf) keeping it farther south and drier for
US. For now have gone with a blend approach with some chance probability of precipitation
and we will have to revisit with later forecasts. A strong surface
ridge builds into the area for Wednesday night and
Thursday....bringing cooler temperatures and hopefully a bit more
sunshine to the region. Lows by Wednesday night and Thursday night
may dip into the 40s again for portions of the area.



&&

Aviation...(for the 06z tafs through 06z Friday night)
issued at 1240 am CDT Friday Aug 22 2014

Mainly IFR/MVFR conditions covered the Northland as of late evening.
Conditions are expected to lower to IFR/LIFR overnight in
fog/stratus. Visibilities will improve Friday morning...and ceilings will
gradually lift as well. Some areas will see VFR conditions by middle to
late afternoon.

A warm frontal boundary south of the Northland was partially
responsible for scattered showers and a few thunderstorms as well.
The coverage of the showers/storms are expected to wane overnight
with a few possible on Friday. Upper level heights will build Friday
and that should help limit the coverage of showers/storms Friday
into Friday evening. More fog/stratus will develop Friday night.



&&

Preliminary point temps/pops...
dlh 71 60 70 61 / 20 10 20 60
inl 76 56 76 58 / 30 10 30 70
brd 79 61 75 64 / 10 10 50 70
hyr 80 61 78 64 / 20 10 40 60
asx 71 59 73 62 / 20 10 20 60

&&

Dlh watches/warnings/advisories...
Minnesota...none.
WI...none.
Ls...Small Craft Advisory until 4 am CDT early this morning for
lsz142>146.

&&

$$

Synopsis...Cannon
short term...Cannon
long term...le
aviation...melde

National Weather Service Glossary of Abbreviations