National Weather Service Raw Text Product

Displaying AFOS PIL: AFDAPX Received: 2018-09-20 14:02 UTC


555 
FXUS63 KAPX 201402
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1002 AM EDT Thu Sep 20 2018

.UPDATE...
Issued at 921 AM EDT Thu Sep 20 2018

Our first classic autumnal synoptic system of the season continues
to slowly take shape in the central plains. More rapid deepening 
will occur tonight and Friday as the system lifts ne, crossing 
upper MI overnight.

A warm front is making northward progress, nearing the southern
border of lower MI. An e-w band of showers/storms is north of the
front. The initial push of more widespread precip has reached nw
lower MI this morning (with sct activity ahead of it). This will
move e or ene across northern MI, with the most substantial rain 
in the south half of the forecast area. A relative lull is seen 
behind this in eastern WI, and a corresponding lull in precip 
chances will cover northern MI by mid-afternoon. 

Meanwhile, healthy destabilization will take place well 
downstate, as they enter into the warm sector. Strengthening 
southerly low- level will advect that flow north of the warm 
front. This should result in spotty deep convection, though 
primarily in southern lower MI. There is still a chance for 
something to ignite this far north. Any PM storms will be well 
elevated, but increasing shear could contribute to supercells and 
a marginal svr hail threat. Deep convection becomes more likely 
after sunset, when the low level jet really starts to crank up.

&&

.NEAR TERM...(Today through Tonight)
Issued at 334 AM EDT Thu Sep 20 2018

High impact weather potential: Widespread showers with perhaps some 
thunderstorms. Marginal risk for an isolated severe thunderstorm or 
two. Primary threat will be damaging winds, and to a lesser extent, 
large hail. 

Pattern synopsis and forecast:

Shortwave troughing was situated over the Rockies early this 
morning, with an associated area of low pressure in the Central 
Plains. A warm front extended east of the low pressure, through 
IL/IN/OH. A fairly extensive corridor of showers and thunderstorms 
was occurring north of this warm front. The convection was being 
fueled by deep moisture (PWATS nearly 2.00") and instability 
(MUCAPES 1000-2000 j/kg), and forced by weak DPVA, but impressive 
right entrance region upper divergence from 120+kt jet across the 
nrn Great Lakes, and pretty strong LLJ/WAA. In nrn Michigan, we 
still had some lingering shallow overlake instability leading to a 
good deal of low cloud, but also had some gradually thickening mid 
and upper level clouds. Some weak vorticity continues to pass the 
region, ejected from the shortwave and traveling through fairly 
strong zonal flow overhead. This was resulting in periodic light 
rain. 

Heading through the day, the Rockies shortwave will eject stronger 
energy into nrn Michigan, while lifting into the central conus, 
before reaching the western Great Lakes tonight. The associated sfc 
low will deepen and track NE, pulling the warm front and corridor of 
showers and embedded thunderstorms into nrn Michigan later this 
morning and afternoon. The warm front exits NE of us tonight taking 
the majority of the rainfall along for the ride, with the system 
cold front arrive by daybreak Friday. The strongest forcing and 
heavier QPF will reside with the deepening sfc low, which tracks off 
to our NW, but regardless, it appears fairly definite that all of 
nrn Michigan will get in on some better rains. Behind the warm 
front, the air mass becomes increasingly unstable into tonight and 
winds are going to be ramping up and becoming gusty in a tightening 
pressure gradient. While convection along the cold front upstream of 
us this afternoon ought to be cranking out some decent storms, much 
of the data suggests that it's activity wanes before/while arriving 
in nrn Michigan. It's another nighttime cold front arrival. We are 
expected to have 1100-1500j/kg of MUCAPE though, and there is at 
least some uncertainty in how much coverage of showers/potential 
storms we will have. Wind fields are quite strong however, with 0-
6km bulk shear 45-60kts, just doubt the instability will be great 
enough to result in a good severe potential. We do remain in the 
marginal risk for severe storms and will thus continue to make 
mention in the HWOAPX. 

Lowered high temperatures today just a bit due to thick cloud and 
rainfall. Readings in the 60s for most areas. Lows tonight will not 
be too far off of that, in the low to mid 60s, temperatures kept up 
by those increasing winds and more clouds. 

&&

.SHORT TERM...(Friday through Saturday)
Issued at 332 AM EDT Thu Sep 20 2018

High Impact Weather Potential: Lingering slight chance of 
thunderstorms through early Friday morning, along with gusty 
northwest winds. Patchy frost possible Saturday morning, primarily 
across the typically cooler/interior locations.

Pattern Forecast: Well-advertised low pressure system is expected to 
be situated across the Ontario/Quebec border come Friday morning 
with a trailing cold front draped southwest across the central U.P. 
through eastern Wisconsin. This front will make rapid progress 
across the area locally early Friday morning with lowering heights 
aloft and strong cold air advection in place through the remainder 
of the day. High pressure gradually presses into the region Friday 
night through Saturday with a return to quiet, but cool weather.

Primary Forecast Concerns/Challenges: Lingering PoPs Friday. Low 
temperatures Friday night/Saturday morning with the season's first 
patchy frost potential.

Aforementioned cold front is expected to cross northern Michigan 
early Friday morning, clearing the entire forecast area by midday. 
Strong cold air advection will become the rule, evident by continued 
gusty northwest winds (25-35 mph) and H8 temps falling from roughly 
15 C Friday morning to 3-4 C Friday evening. Lingering low level 
moisture behind the front may allow for occasional shower activity 
to continue off and on, especially downwind of Lake Michigan and 
Superior as lake processes may even play contributor given 
increasing over-lake instability (delta Ts nearing 20 C). 

High pressure gradually presses into the area Friday night bringing 
a much drier airmass and a return to precipitation-free conditions 
across all of northern Michigan. The biggest question through the 
forecast period revolves around how quickly clouds clear Friday 
night, which will play largely into overnight low temperatures and 
potential patchy frost. Current trends suggest skies clearing from 
west to east after sunset with mostly clear conditions in place by 2-
3 AM (along with rapidly decreasing surface winds), which would 
leave several hours of strong radiational cooling and the potential 
for temperatures to drop into the mid 30s for the typically cooler/ 
interior locations of both eastern upper and northern lower. Will 
continue to trend the forecast in that direction with lows bottoming 
out in the mid-30s for the areas mentioned above (much warmer in the 
Great Lakes collar counties).

Mostly sunny and dry conditions expected Saturday as high pressure 
becomes centered directly overhead. High temperatures several 
degrees below normal...ranging from the upper 50s to low 60s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 332 AM EDT Thu Sep 20 2018

High Impact Weather Potential: Another patchy frost threat Sunday 
morning. Otherwise, minimal for now, although watching thunderstorm 
potential early next week.

Potential for another chilly night Saturday night with temperatures 
once again bottoming out in the 30s across the typically cooler 
locations of northern Michigan. Will continue to make mention of 
another night of patchy frost potential. Otherwise, focus turns 
toward early next week as another system develops across the 
plains...able to tap into Gulf of Mexico moisture before trekking 
northeastward toward the western Great Lakes. Lots of uncertainty 
regarding this system given it being 5+ days out, but it certainly 
seems as if it'll carry the next chance for widespread precipitation 
across northern Michigan.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 648 AM EDT Thu Sep 20 2018

Low pressure in the Central Plains will deepen today and into
tonight, as it lifts into the nrn Great Lakes. The system warm
front lifts through nrn Michigan late today and into this evening,
with a cold front arriving late tonight into Friday morning.
Showers and perhaps some thunderstorms will follow the spits of
light rain currently out there, arriving this morning and 
afternoon, with activity becoming more isolated/scattered into 
tonight. MVFR/possible IFR CIGS will prevail, before conditions 
eventually turn VFR behind the warm front. Also, winds will ramp 
up and become gusty tonight. Am a little uncertain as to how 
gusty, and the impact they may have on LLWS, as even stronger 
winds develop just off the ground. However, winds at 2kft are 
expected to quickly ramp up to 35kts this evening, and then to 
45-50kts after midnight. Despite gusty sfc winds, will mention the
stronger LLWS.


&&

.MARINE...
Issued at 332 AM EDT Thu Sep 20 2018

Low pressure in the Central Plains will deepen today and into 
tonight, as it lifts into the nrn Great Lakes. The system warm front 
lifts through nrn Michigan late today and into this evening, with a 
cold front arriving late tonight. Widespread showers and perhaps 
some thunderstorms will arrive this morning, with activity becoming 
more isolated/scattered later today and into tonight. More 
importantly, winds will be increasing later today through tonight, 
and will remain strong through Friday, with gale force speeds over 
most nearshore waters. High pressure arrives Friday night and holds 
through the weekend. 


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT from 5 PM EDT this afternoon through 
     Friday evening for MIZ024-030-036-042.
LH...GALE WARNING from 8 PM this evening to 8 PM EDT Friday for 
     LHZ345.
     GALE WARNING from 8 PM this evening to midnight EDT Friday night 
     for LHZ346>349.
LM...GALE WARNING from 8 PM this evening to 8 PM EDT Friday for 
     LMZ323-341-342-344>346.
LS...GALE WARNING from 8 PM this evening to 8 PM EDT Friday for 
     LSZ321-322.
&&

$$

UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...MG
LONG TERM...MG
AVIATION...SMD
MARINE...SMD