Area Forecast Discussion
Issued by NWS Gaylord, MI

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353
FXUS63 KAPX 222020
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
420 PM EDT Wed Mar 22 2017

.NEAR TERM...(Tonight and Thursday)
Issued at 351 PM EDT Wed Mar 22 2017

...Clear, cold, and calm tonight...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Anomalously strong (2 to 3 standard
deviations above the mean) Canadian high pressure system currently
centered over the Upper Great Lakes will slowly drift southeast
across Lower Michigan overnight, reaching Pennsylvania by daybreak
Thursday. Strong subsidence and a very dry airmass associated with
this system have allowed for clear as a bell skies across northern
Michigan this afternoon, with the exception of some thin cirrus
spilling into eastern upper. Expecting upstream cirrus to
continue thinning out as it encounters the drier airmass over the
region this evening, so skies should remain clear across a
majority of the forecast area through the first half of tonight.
Mid/high clouds will start to increase from the west after
midnight ahead of the next approaching system. As the high departs
on Thursday, southerly return flow will develop over northern
Michigan, but the very dry airmass should inhibit any showers from
developing most of the day. A shortwave will interact with
increasing WAA and a low level jet over northern Minnesota to
generate showers out there around daybreak. Will have to watch how
this activity holds together as it slides east across the Upper
Peninsula Thursday morning. Thinking the lower levels will still
take quite some time to moisten up, so only a small chance for
perhaps an isolated shower across western Chip/Mack counties by
Thursday afternoon. Otherwise the bulk of precip in our forecast
area will hold off until Thursday evening.

Primary Forecast Concerns...Low temperatures tonight will be the
main forecast concern. Despite the stronger late March sun angle,
temperatures today were running about 10 degrees below normal due to
the unseasonably cold airmass in place, unable to even reach 30F in
many locations. This leads to concern about how far temperatures
will drop heading into tonight with a very favorable radiational
cooling setup in place: light to calm winds, a very dry airmass
(dewpoints generally single digits below zero to around 10F this
afternoon), and clear to mostly clear skies for most of the night.
Raw deterministic guidance for lows tonight is way too warm
(suggesting teens north to 20s south). Though perhaps a bit too
cold, MOS guidance looks more reasonable, so have weighted tonight`s
lows more towards MOS. At this time, expect single digits to teens
across the entire area, but evening shift will have to watch trends
and evaluate if this is low enough.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 351 PM EDT Wed Mar 22 2017

...Unsettled pattern begins...

Energy moving off the Pacific will approach the Great Lakes region
late this week and likely linger all the way into early next week
due to a rather blocky pattern. Low level cold air cycling
southwestward around strong high pressure to the north may present
precipitation type issues (mainly at night) as warmer air advects in
at mid levels. Precipitation type will be the biggest challenge over
the next few days.

Thursday night...Mid/upper level and eventually low level moisture
increase out ahead of a surface warm front to our south. Plenty of
mid level warm advection with 850 mb temperatures rising to a few
degrees above zero across northern lower and to near zero in
eastern upper by 12z Friday. However...strong surface high (1032
mb) to the north across Ontario cycles in cold air at the surface.
This in combination with evaporative cooling as surface dewpoints
start off in the single digits and teens could lead to some
freezing rain and possibly even a little sleet initially I suppose
depending upon the timing (dry easterly flow will be slow to
moisten up fully to support precipitation). The only place I could
see any snow initially is across eastern upper where the warmer
mid level air arrives last. Still too early to pin down ice
accumulations (but likely a tenth of an inch or less) or possibly
headlines.

Friday into Saturday...Continued warm advection aloft with the
surface warm front likely remaining to our south. This will present
an overrunning situation likely leading to more precipitation. As
was the case initially, the strong surface high to the north should
continue to cycle in cold air. Given that it`s late March surface
temperatures will likely warm enough during the day to support all
rain. At night with nocturnal cooling, freezing rain may become an
issue. The freezing/or not freezing is borderline so it will likely
be a near term issue based on current trends as to whether headlines
will be needed. The best chance of occurrence is across the northern
forecast area and over the higher terrain.

&&

.LONG TERM...(Friday night through Wednesday)
Issued at 351 PM EDT Wed Mar 22 2017

High Impact Weather Potential...Periods of icing potential this
weekend in the interior portion of N Lower and in E Upper.

Occluding low pressure will be moving through the area this weekend.
With rain expected during the day Saturday, temperatures dropping
below freezing overnight could make for slick surfaces. Potential
for a period of freezing rain continues to be a concern as well.
Have FZRA in the grids for Saturday night, but the extent, timing,
and placement will certainly change over the next few days. Surface
temps in many areas are very close to the freezing mark, so
confidence this far out is moderate at best, as even a slight uptick
could leave just rain, minus the freezing aspect. This is a slow
moving system that could produce precipitation into early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 123 PM EDT Wed Mar 22 2017

VFR conditions will continue through the TAF period as a strong
Canadian high and dry airmass move across the Upper Great Lakes.
Just a bit of passing cirrus this afternoon and evening until
mid/high level clouds start to increase late tonight through
Thursday morning ahead of the next approaching system. Generally
northerly winds this afternoon will become light and variable this
evening as the high passes overhead. Winds will shift to the SSE
Thursday morning, becoming slightly stronger than today.


&&

.MARINE...
Issued at 351 PM EDT Wed Mar 22 2017

Winds will become light and variable late this afternoon into early
evening as a strong surface high drifts across the area. Late
tonight as the high begins to depart, winds will become more
southerly, steadily increasing through the day Thursday and perhaps
reaching small craft advisory levels in some areas by Thursday
evening. Winds will then diminish through the second half of
Thursday night.

&&

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

$$

NEAR TERM...MEK
SHORT TERM...AJS
LONG TERM...ALM
AVIATION...MEK
MARINE...MEK



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