Area Forecast Discussion
Issued by NWS Duluth, MN

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327
FXUS63 KDLH 261728
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1228 PM CDT FRI AUG 26 2016

.SHORT TERM...(Today through Saturday)
Issued at 349 AM CDT Fri Aug 26 2016

After a chilly morning with lows in the 40s in some areas and patchy
fog skies will be mostly sunny today as high pressure builds in
across the upper Midwest. Increasing clouds and showers possible
late tonight into Saturday. Temperatures remaining on the cool side
for late August with highs in the upper 60s to low 70s today and
tomorrow and lows in the 50s tonight.

On the synoptic scale an area of high pressure centered over the mid-
Mississippi river valley this morning will gradually build eastward
towards the Great Lakes today. At upper levels of the atmosphere an
upper high will be centered over central Appalachia today while a
shortwave trough across southern Saskatchewan/eastern Montana
approaches from the west. This will all result in southerly flow at
low to mid levels today, bringing some milder air into the upper
Midwest, warming up from 850mb temps around +6 to +8C this morning
to +10 to +12C by 00z this evening. Skies will initially be mostly
sunny, but with steep low level lapse rates from diurnal heating
expect a bit of fair-weather cu developing by the late morning/early
afternoon, similar to the central Dakotas today. More clouds
towards the evening as the shortwave trough approaches from the west
with a large area of mid-level moisture currently over the central
and northern high plains advecting towards the mid to upper
Mississippi river valley.

Precipitation may begin late Friday night across north-central
Minnesota in the warm air advection regime, but the better large-
scale forcing doesn`t really arrive until Saturday when the best PVA
happens. While there is a chance for rain across the entire
Northland Saturday, there are really two separate areas with the
best chances for precip. First, across north-central to northeast
Minnesota (mainly along and northwest of the Iron Range) showers and
storms are expected to move in from the west in the afternoon after
initiating across the Red River Valley in the morning, with strong
large-scale forcing and a bit of an EML advecting in from the west
resulting in a chance for some embedded thunderstorms. Second,
showers and thunderstorms will develop across the eastern central
Plains into the mid-Mississippi valley late today into tonight along
a warm frontal zone. This area of convection will then advect north,
possible impacting parts of northern Wisconsin by Saturday. However,
best instability would be further south, resulting in a low to nil
chance for thunderstorms Saturday afternoon. The margin of error for
the best chances for precip from both of these sources is wide
enough that the entire area has a chance for rain Saturday.

.LONG TERM...(Saturday night through Thursday)
Issued at 349 AM CDT Fri Aug 26 2016

Saturday evening the strong shortwave and associated convection will
sweep northeast out of the region, leaving mainly showers for the
rest of the night. Have maintained some fairly high pops in the
evening time frame, but reduced them to slight chances or less for
after midnight.  We should have at least a short period of quiet
weather Sunday morning, but during the afternoon and evening there
is potential for new thunderstorm development over central Minnesota
that should also sweep northeast across the forecast area Sunday
night and linger into Monday. Models are picking up on the
instability that develops for Sunday afternoon, but not all are
developing convection as the shear and trigger look weak with a cold
front still out over the Dakotas.  Have used the GFS more in
developing this convection, but have kept pops to slights and small
chance pops.  Convection continues on Monday and Monday night with
the cold front that pushes through during the day and early evening.
We finally get a break in this active weather pattern for Tuesday as
a ridge of high pressure builds across the area.

Uncertainty gets larger into the middle of the week as an upper
level ridge builds over the high plains, which should push an 850mb
baroclinic zone across the region for convection to develop upon.
Have had to keep chance pops going through the remainder of the
forecast period with that feature in place through the end of the
week and various shortwave sliding down the northwest upper level
flow interacting with it.  We will continue our relatively warm
pattern with near to above normal temperatures through the
extended.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1228 PM CDT Fri Aug 26 2016

VFR conditions expected for much of the upcoming forecast. High
pressure will build eastwards into the central Great Lakes by this
evening. This will keep southwesterly winds this afternoon with
fair weather cumulus lingering around into the evening. Based on
obs and the latest HRRR/RAP/NAM output expect cumulus ceilings
between 4-6 kft. Cumulus will dissipate during the evening due to
the loss of heating.

Winds will be light, but cloud cover will increase overnight as a
trough digs into the Northern Plains. There is a possibility of
radiation fog developing, but uncertain how widespread fog will be
due to the increasing cloud cover. For now kept a mention of fog
at KHYR, but may need to include at KHIB if cloud cover increases
slower than currently thinking. Kept in VCTS at KBRD/KINL from 14Z
until the end of the TAF. Think that showers/storms are possible
at other terminals after 18Z per the latest GFS/ARW/NMM.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  73  54  68  54 /   0  30  60  50
INL  75  55  68  52 /   0  40  60  40
BRD  74  57  71  56 /   0  50  50  30
HYR  73  54  69  55 /   0  30  70  30
ASX  73  54  71  57 /  10  20  60  40

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...JJM
LONG TERM...LE
AVIATION...WL



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