Area Forecast Discussion
Issued by NWS Gaylord, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

398
FXUS63 KAPX 272020
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
320 PM EST Mon Feb 27 2017

.NEAR TERM...(Tonight and Tuesday)
Issued at 248 PM EST Mon Feb 27 2017

...Wet weather arrives Tuesday...

High Impact Weather Potential: Nothing too significant. Will need to
watch for some light mixed precipitation potential early Tuesday.

Pattern Synopsis/Forecast: Deep southwest flow becoming increasingly
established this afternoon in response to digging Intermountain West
troughing. Morning overhead cold front has essentially washed out as
light southerly surface winds have developed on backside of
retreating surface high. That high has resulted in mostly sunny
skies across much of northern lower Michigan, with just some passing
mid and high clouds across areas north of the bridge. Combination of
that sun and southerly flow has done a pretty good number on
temperatures this afternoon across northern lower, with readings
making a run well into the 30s and 40s.

Mild trend continues through Tuesday as that southwest flow only
strengthens with time. These winds eventually bring in a surge of
deeper moisture, with passing subtle mid level wave working on such
to kick off some light precipitation on Tuesday.

Primary forecast concerns: Addressing precipitation timing and type
on Tuesday.

Details:  Not a whole lot going on tonight. Top-down moisture
advection increases in that southwest flow, as noted by steadily
increasing high and mid level clouds. Dry lower levels will be last
to saturate, and likely taking until almost sunrise to do so, and
then only across our far southwest. Sounding suggest a deep enough
melting layer to support all liquid reaching the surface. Those
surface temperatures also look mild as maintenance of light
southerly winds and those increasing clouds look to keep
temperatures several degrees above freezing. While not totally out
of the question that any precip begins as a wintry mix given
evaporational cooling potential, any impacts should be minimal.
Elsewhere, expect dry conditions under that slowly increasing cloud
cover. Temperatures will likely stabilize or even slowly rise
overnight as those clouds increase.

Above trend continues into Tuesday as deeper moisture surges
northeast, completing low level saturation in the process. Core of
elevated mid level lapse rates may also help the precipitation
generation and intensity cause. Question becomes one of
precipitation type, although "mild" start to the day and elevated
warm nose running lockstep with moisture surge sure argues for
mainly a rain event. Much like the overnight, suppose a bit of
snow/light wintry mix of precipitation is possible at the very
beginning until full saturation is complete. Shouldn`t be much for
sure, with little if any snow accumulation expected. Of course,
bigger issue may be rain falling on those already ice covered
secondary roads (those that haven`t fully melted today). A mild day,
despite the rain and low clouds, with highs well up into the 40s for
northern lower and just a few degrees cooler north of the bridge.

&&

.SHORT TERM...(Tuesday night through Thursday)
Issued at 248 PM EST Mon Feb 27 2017

...Rain Tuesday night transitions to snow Wednesday...

High impact weather potential: Accumulating snow possible Wednesday
afternoon-evening, highest across the southeastern half of the CWA.

Pattern Forecast: Tuesday night, the main focus lies around a buckle
in the jet stream across the Intermountain West with a well defined
longwave trough and several embedded small shortwaves centered lee
of the Rockies. As the large-scale open wave and strung out mid-
upper level energy ejects toward the Great Lakes Tuesday-Tuesday
night, associated surface low pressure continues to strengthen. As
the surface low continues to trek eastward and a secondary shortwave
races through the mean flow during the day Wednesday, concern is
raised for a period of accumulating snow across a portion of the
area as much cooler air filters into northern Michigan. Broad
northwesterly flow under weak troughing continues for the remainder
of the short term forecast period before ridging takes over this
weekend.

Primary Forecast Concerns: The main forecast concern and
uncertainties revolve around Wednesday, despite ongoing rain
(perhaps a few rumbles of thunder in southern sections?) across the
majority of northern Michigan Tuesday night. No glaring reason to
deviate from the going categorical PoPs Tuesday evening with a
gradual diminish of coverage and intensity expected after midnight
as the best surge of moisture accompanies the system`s eastward
progression. In general, another 0.15-0.35" of rain expected
(highest southeast).

Forecast challenges increase late Tuesday night and especially
Wednesday as an embedded secondary shortwave races through longwave
troughing overhead. This will help to reinvigorate synoptic support
while tightening a low-mid level baroclinic zone draped across the
state of Michigan by midday Wednesday. As much cooler air begins to
filter into northern Michigan from the northwest early Wednesday
morning across eastern Upper and through the remainder of the day
south of the bridge, a transition from rain to snow showers is
expected. By the midday hours and especially during the afternoon,
the aforementioned tightening baroclinic zone is progged by nearly
all deterministic guidance to focus a swath of respectable fgen
response and accumulating snowfall across at least a portion of the
area. If current trends continue, it certainly looks as if several
inches of wet, heavy snow will be possible; however, there remains
hesitation at this juncture to pinpoint any specific locations as
the swath of heaviest snow may remain fairly narrow and will likely
bounce around a bit over the next 48 hours as guidance continues to
struggle with Wednesday`s overall evolution. It does look like the
most likely broad area for a period of respectable snowfall lies
southeast of a Houghton Lake to Alpena line with lesser amounts to
the northwest. This thought lines up fairly well with WPC`s Day 2
winter weather outlook, which suggests a 40-70% chance of at least 4
inches just north of Saginaw Bay.

Scattered lake effect snow showers beyond Wednesday certainly
continue to look like a possibility in NW/NNW favored areas as
marginally cold enough air (H8 varies from -10 to -12 C Wednesday
night through Thursday) temporarily takes hold across the northern
Great Lakes. Low-mid level moisture is paltry at best, so snow
shower coverage/intensity may be lacking through that time frame.

&&

.LONG TERM...(Thursday night through Monday)
Issued at 248 PM EST Mon Feb 27 2017

Ongoing lake effect Friday will diminish Saturday as high pressure
passes to our south. Another clipper will push through over the
weekend, and could bring some mainly light rain or a rain/snow mix
for some. Weekend highs will be well above normal, so any snow
mixing in will be overnight. The most notable feature is a possible
storm early next week. Still a lot of uncertainty with the
particulars, but this could be a robust system. Will see how it
develops in the coming days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1224 PM EST Mon Feb 27 2017

No concerns through tonight as high and mid level clouds only
slowly increase. Lower cloud deck and the threat for light
rain/mist spread from southwest to northeast Tuesday, brining MVFR
to IFR conditions across the taf locations. Light winds through
this forecast period.

&&

.MARINE...
Issued at 248 PM EST Mon Feb 27 2017

Light south and southeast winds do increase overnight, with
some low end SCA conditions becoming possible by Tuesday morning,
especially over some of the nearshore waters of Lake Huron. Passing
low pressure swings the winds around to a more northerly direction
later Tuesday night and Wednesday. Onset of cold air advection will
result in increasing over-water instability and gusty winds.
Widespread SCA conditions are likely during this period, with even
some concern for isolated gale force wind gusts.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...MSB
SHORT TERM...MJG
LONG TERM...ALM
AVIATION...MSB
MARINE...MSB



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.