Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
440 am EST Wednesday Feb 10 2016
issued at 439 am EST Wednesday Feb 10 2016
Lake effect snow showers will continue through daybreak and will
be locally heavy at times. Snowfall rates of 1 to 2 inches per
hour are possible in the strongest bands. Snow showers will lessen
in intensity but still persist through Thursday. While most
locations should see at least some measurable snowfall during this
period...the more significant amounts and greatest impacts will be
confined to the favored lake effect snow belt region. Highs
Wednesday in the upper teens and lower 20s with lows Wednesday
night ranging from the single digits away well away from Lake
Michigan to the teens elsewhere.
Short term...(today through thursday)
issued at 437 am EST Wednesday Feb 10 2016
..extended period of snow showers to continue...
Widespread snow showers were impacting much of the forecast area as
extensive lake response continues. That being said...accumulations
have generally been confined to 1 or 2 dominant snow bands that have
generally remained transitory. The first band...was located from
southern Berrien County southeast across much of St. Joe County in Indiana
and into portions of Marshall and Kosciusko counties. A second
band has set up from Three Rivers Michigan southeast to northwest of Albion. Local
visibilities have dropped briefly to around a half mile at times
with locations under the bands likely seeing a quick few tenths to
one half inch of snow.
Arw has generally handled evolution of snow bands the best so will
lean somewhat towards it with partial nod to NAM. Challenges lie
today with exact placement of snow bands...coverage and effects of
dry air entrainment arriving from Wisconsin where surface dewpoints were
dropping below zero. This has cut down the extent of snow band
production well out into the lake but other parameters and effects
of soon to depart short wave all helping keep things going. Think
that many areas will still see light snow showers or flurries with
heaviest snow showers in current advisory area through the day. Most
locations will see little more than a dusting during the day but
localize areas could see 1 to 2 inches of snow by later this
afternoon closer to favored lake effect areas.
Inversion heights...fetch and alignment of dgz and best Omega will
all remain favorable to keep snow showers production ongoing into
Thursday morning with diminishing accumulation potential as you move
further inland. The near surface dry air entrainment will likely
help limit overall accumulations but still should yield 1 to 4
inches locally across mainly the advisory area.
By Thursday afternoon...flow will become more west and SW as brief
ridging shifts the snow showers into western Michigan.
Long term...(thursday night through tuesday)
issued at 437 am EST Wednesday Feb 10 2016
Overall synoptic pattern characterized by a positive pna pattern
with large scale upper trough over the eastern Continental U.S. And a ridge
over the west. Upper levels will flatten subtly during this long
term period as North Pacific wave train temporarily flattens western
ridging. However...weakening polar vortex will allow an upper low
and a shot of very cold siberian air to penetrate south into the
northeast Continental U.S. By this weekend...skimming the western Great Lakes.
Pacific energy trailing this Arctic cold will reinforce Great Lakes
troughiness but also allow a slow moderation in temperatures by early next
week as main cold core exits.
Numerous short waves and periods of lake effect snow expected during
this period. Timing of short waves and location of lake effect
remain difficult at these time periods so continued with broad brush
probability of precipitation. Did favor European model (ecmwf) slightly but stayed close to overall
superblend init. Raised probability of precipitation to high chance Friday night into
Saturday in favored lake effect regions given surface-850mb Delta T
values in middle 20s. Little synoptic moisture with Arctic air and dgz
near ground level will likely inhibit big snowfall but long fetch
and pre-conditioning off Lake Superior warrants close watching next
few days. European model (ecmwf) also rather aggressive with a short wave Monday
bringing deeper moisture and swath of snow into eastern areas. Kept
probability of precipitation in the middle chance category for now with a lot of uncertainty.
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1243 am EST Wednesday Feb 10 2016
Lake effect snow showers and impacts at terminals main focus this
package. Kiwx 88d shows strong band just north of ksbn at issuance
time and sinking south. Should see LIFR and vlifr conditions next
few hours as a few surface reports under this band indicated near
zero visibility and heavy snowfall rates. Hires models indicate
this band to weaken overnight or at least translate away from
ksbn so slightly improved conditions after 09-10z. Persistent northwest
flow and cold air will likely keep MVFR and IFR conditions with
snow showers through rest of period at ksbn. Kfwa remains on
eastern edge of snow showers and expect varied conditions with
MVFR in snow showers with brief periods of IFR not out of question
through middle morning with a few stronger showers that remain
intact well inland.
in...Winter Weather Advisory until 10 am EST /9 am CST/ Thursday for
Michigan...Winter Weather Advisory until 10 am EST Thursday for miz077>079.
Lm...Small Craft Advisory until 4 PM EST Thursday for lmz043-046.
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