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Office: MPX

FXUS63 KMPX 160503
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1103 PM CST Fri Dec 15 2017

.UPDATE...
Issued at 1034 PM CST Fri Dec 15 2017

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 301 PM CST Fri Dec 15 2017

Today and tonights forecast is pretty straight forward but there's
some uncertainty on when exactly the snow will start and when it
will end. Regardless it does appear like most locations,
especially along and north of I-94, will get light snow this
evening and overnight so increased pops in this area. This system
is pretty weak and quick-moving so dont anticipate any areas
receiving more than about 2 to 3 inches. Saturday will be
seasonably mild with cloudy skies and light winds.

The main driver for the snow that is expected to move across the
region is the isentropic lift associated with the low level
Theta_E advection. The wind is pretty uniform across the
isotherms, so there is not much Fgen meaning this should be a more
wide-spread light snow event vs a concentrated narrow have band
that accompanies strong Fgen. Forecast soundings seem to echo this
as well with a broad area of weak omega that saturates the column
and leads to several hours of light snow. The 15.12 ECMWF with
its broad area of light QPF paints this picture nicely.

There is already plenty of low level moisture in place as evident
by the widespread stratus, and a few locations have been
reporting light snow all morning across western MN. It stands to
reason that light snow should develop rather quickly once the
better forcing with the isentropic lift moves across the region.
For that reason, sped up the timing of pops this afternoon and
increased them later this evening. Ended up decreasing snowfall
amounts a little bit, but still have higher confidence that light
snow will indeed fall over the next 12 hours, just not as much.

.LONG TERM...(Saturday night through Friday)
Issued at 301 PM CST Fri Dec 15 2017

Sunday will be dry and mild with most locations seeing highs in
the lower 30s. Another clipper system will bring snow across
northern MN/WI on Monday but most of this will miss the forecast
area. The relatively warm weather will continue Tuesday into
Wednesday as well as zonal flow continues across the region. Snow
should develop to the north Wednesday night and there is a chance
it could spread southward across the region on Thursday and
Thursday night. The Thursday system has lower confidence, but this
storm has been trending drier and weaker so at this point is
appears that a winter storm is unlikely for the latter part of
next week.

A positively tilted trough will crawl down the west coast on
Wednesday, while a northern stream jet strengthens as it crosses
an upper level ridge over British Columbia. The GFS/ECMWF have
been stronger with this jet and this end up forming a cutoff low
across the Baja. Meanwhile the northern stream continues in a
progressive positively tilted upper level wave over the central
Conus which is not favorable for cyclone development. The 15.00
ECMWF brought an area of vorticity across the Midwest which did
produce a snowstorm, but the GFS 15.12 resembles a more realistic
scenario with a cold front and some light snow moving though the
region followed by cold air for the weekend. The ECMWF 15.12 has
backed off slightly as well, but still brings a few inches of snow
across the southern half of Minnesota and most of Wisconsin, so
continued with 40-50 pops.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1034 PM CST Fri Dec 15 2017

The fairly wide band of light-moderate snow has shown signs of
shrinking through the evening hours as it as been sliding
southeast across MN and WI. This trend is expected to slowly
continue through the early morning hours but the most persistent
-SN will occur mainly over the WI TAF sites. Ceilings will
 generally run in the MVFR range for all terminals, with KAXN most
 susceptible to IFR ceiling into the early morning hours.
 Visibilities will generally run in the VFR range but isolated
 heavier bursts of snow may well produce brief bouts of IFR
 visibility. Once the main swath of snow diminishes during the
 early morning hours, scattered flurries and snow showers will
 persist mainly over the eastern MN and western WI through
 daybreak.

KMSP...Steady -SN has shifted east of MSP in the last couple hours
with only flurries and/or snow showers expected through daybreak.
Ceilings are expected to drop back into MVFR range during the
pre-dawn hours and remain in MVFR range through tomorrow evening.
A period of ceilings sub-1700ft may potentially develop during
the evening push tomorrow but isn't expected to be long-lasting.

/OUTLOOK FOR KMSP/
Sun...Mainly VFR. Chc morning MVFR. Wind variable 5 kts or less.
Mon...VFR. Wind SW 10 kts.
Tue...VFR. Wind NW 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...jrb
LONG TERM...JRB
AVIATION...JPC



Office: DLH FXUS63 KDLH 160856 AFDDLH Area Forecast Discussion National Weather Service Duluth MN 256 AM CST Sat Dec 16 2017 .SHORT TERM...(Today through Sunday) Issued at 254 AM CST Sat Dec 16 2017 A broad area of surface low pressure stretched from southern Minnesota northwest into Saskatchewan this morning. The low will move little and gradually weaken over the next 12-18 hours. However, a shortwave will move in from the northwest today with low level warm air advection/FGEN continuing. Light snow was falling early this morning from the Phillips/Park Falls area, northwest through the Twin Ports toward Bigfork, Walker, and Grand Rapids. Easterly low level flow will was also producing some lake effect snow as seen on KDLH radar between Two Harbors and Silver Bay as of 0850Z. Light snow will continue this morning and gradually move east and north. Lake enhanced snow will be possible through the evening along the North Shore. Forecast soundings show some drying aloft which will cause a loss of ice today into tonight over much of the area. This may lead to areas of freezing drizzle this morning over parts of central and northern Minnesota with chances then developing over the rest of northeast Minnesota into northwest Wisconsin. At this time, amounts look light and we will not be issuing a Winter Weather Advisory but will issue a Special Weather Statement to highlight the threat. Most areas will receive less than an inch of snow today with the exception of locations along the North Shore. The low level flow was east early this morning but is forecast to veer to east southeast through the morning, then to south this evening and to southwest overnight. We expect snowfall from just northeast of the Twin Ports to Grand Portage to range from 1 to 4 inches today with some locally higher amounts possible. The precipitation will come to end tonight with Sunday expected to be dry. Plenty of clouds are expected today and tonight but a decrease in clouds should develop through the day Sunday over northern Minnesota but clouds are expected to remain over much of northwest Wisconsin. Expect highs today in the teens over the Arrowhead and Borderland, to the lower to middle twenties most other areas. Sunday will be warmer with highs from the mid twenties to around thirty. .LONG TERM...(Sunday night through Friday) Issued at 254 AM CST Sat Dec 16 2017 A brief period of above-normal temperatures to start off the work week, then the arctic air and below-normal temperatures return mid to late week and stick around for the foreseeable future. A chance for light snow Monday across northern Minnesota then a widespread chance for snow Wednesday into Wednesday night, with periodic chances for light lake effect snow showers along the south shore snow belt region through the long term forecast period. On the synoptic scale a warm front builds into the Upper Midwest this weekend with warm air advection causing 850mb temps to rise to near 0C in central Minnesota on Monday afternoon with highs in the 30s across the Northland, around ten degrees above normal. The warm air does not last long as a cold front moves from west to east across the region late Monday with a chance for snow along and ahead of the front. Snowfall amounts are expected to be on the light side, around an inch or so mainly limited to northern Minnesota during the day and evening hours on Monday. A more organized pattern develops towards mid-week as an amplified mid-level shortwave trough enters the the Pacific Northwest Tuesday night and digs southeast towards the Four Corners region on Wednesday. A secondary mid-level shortwave trough will track east across the Canadian Prairie into the northern Plains during this time along the same trough axis, causing two areas of low pressure to deepen - one over the Northern Plains and another over the southern High Plains. As the northern low deepens a broad precipitation shield will develop and build into the region Wednesday as a warm front lifting north then pivoting and transition to a cold frontal boundary as the two areas of low pressure combine and a strong cold front with 850mb temps below 0C reach as far south as Texas tracks east across the Mississippi River Valley towards Appalachia late- week. For the Northland this pattern will result in a broad area of precipitation chances Wednesday into Wednesday night followed by below-normal temperatures into next weekend. Snowfall amounts Wed/Wed night could be in the 3-5 inch range for a broad area of Minnesota and Wisconsin, but determining exactly where the axis of higher snowfall amounts will be at this point is difficult. The 00z ECMWF, GFS, and many GEFS members have this axis over northern MN/NW Wisconsin, but the Canadian has the axis further south which would result in little snowfall for the Northland. There is a potential for this pattern to support heavier snowfall amounts per GEFS and ECMWF ensembles, but the spread of ensemble guidance and the difficultly of predicting where the frontal axis will line up due to complexities in the broad pattern lead to below normal confidence in the forecast. Beyond the snowfall chances mid-week temperatures will plummet to below normal values as arctic air returns. The holiday weekend into Christmas Day on Monday looks to be especially chilly with some model solutions limiting high temperatures to the single digits above or below zero Sunday and Monday. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1144 PM CST Fri Dec 15 2017 Light snow has brought an area of MVFR/IFR ceilings and MVFR visibilities to mainly KBRD, KDLH, KHIB and KHYR as of issuance time. Expect this to continue through no later than 12z as the snow band moves across the area, with no worse than IFR conditions expected. Another, weaker round of light snow or flurries to move in after 15z and continue through about 21z, with mainly MVFR ceilings and visibilities. A drying trend may bring improving conditions to KINL and KBRD after 03z, but timing is uncertain and have left out for now. && .PRELIMINARY POINT TEMPS/POPS... DLH 22 15 29 18 / 70 10 0 0 INL 18 14 29 18 / 60 40 0 0 BRD 26 17 32 19 / 30 10 0 0 HYR 24 17 30 17 / 60 10 10 0 ASX 23 16 31 18 / 40 10 10 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory until 4 PM CST this afternoon for LSZ141>143. && $$ SHORT TERM...Melde LONG TERM...JJM AVIATION...LE