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Displaying AFOS PIL: AFDGRR Received: 2019-04-15 07:30 UTC


164 
FXUS63 KGRR 150730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Mon Apr 15 2019

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 330 AM EDT Mon Apr 15 2019

- Clearing skies and warm temperatures today will start melting
  the snowpack helping power recovery efforts.

- A stalled frontal boundary will allow for multiple chance for
  precipitation tonight through the middle of next week. 

- Thunderstorms are possible Thursday--the intensity of which
  still very much so in question. 

&&

.DISCUSSION...(Today through next Sunday)
Issued at 330 AM EDT Mon Apr 15 2019

Radar returns are finally disappearing this morning after a rather 
impressive April snowstorm.  A band of 7-10" of "concrete" snow (0.8-
1.0" of liquid equivalent) fell from around Muskegon to Clare, 
leading to downed tree limbs and thousands of homes and businesses 
without power as of this writing. Yesterday featured the 5th highest 
snowfall for any April calendar day in Muskegon, with record daily 
snowfall being observed in Grand Rapids and Muskegon. So...not your 
average snowstorm. Even while the snow has stopped falling, a few 
slick spots are are still likely out there (especially on back/side 
roads) so exercise caution for the morning commute. Clearing skies 
this morning will provide access to a strong April by mid-afternoon, 
though it'll be hard to fully melt everything away today given the 
high water content of the snowpack (mainly where more than 3" fell). 
As such, we anticipate an interesting temperature gradient by this 
afternoon; low to mid-40s across the west with lower 50s across the 
southeast. 

Starting tonight, we will find ourselves along the northern side of 
a low-level warm front beneath zonal upper-level flow placing Lower 
Michigan in a preferred location for periodic precipitation through 
the middle of the week. Broad synoptic-scale ascent in the right 
entrance region of an upper-level jet streak within the 
aforementioned zonal flow aloft will allow for an increase in mid-
level cloud cover this evening from west to east. As modest warm-air 
advection commences toward midnight tonight, a narrow band of 
precipitation is expected to develop along the frontal zone //and 
across central Lower Michigan// and persist through much of Tuesday 
(though note initially dry low-level air will likely inhibiting 
anything from reaching the ground until around daybreak). While 
precipitation rates/totals are not expected to break the bank, weak 
forecast mid-level instability may allow for a few healthy downpours 
all in all translating to a narrow swath of a few tenths of 
precipitation by Tuesday evening.

Low-level clouds and drizzly conditions are likely to prevail 
Wednesday as broad low-level isentropic ascent continues atop the 
frontal boundary. Showery activity will increase in coverage 
Wednesday afternoon in tandem with increasing southwesterly flow as 
a low pressure system approaches from the southwest. By Thursday 
morning, the low pressure system is expected to be somewhere in the 
vicinity of northern Illinois with strong southerly low-level flow 
finally placing central Lower Michigan in the warm sector of the 
system. Now I have to be honest, convective chances Thursday 
afternoon/evening are unclear and appear rather similar to our set-
up exactly a week ago. Strong low-level shear will be present, but 
instability (surface-based at least) may be hard to come by thanks 
to abundant low-level clouds (e.g. convection to our south) and 
unfavorable timing of a cold frontal passage. All in all, we can't 
write off Thursday for severe weather but concern at this point is 
on the low-end. Showery activity (at times with a few snowflakes?) 
will likely persist Friday and Saturday as the low pressure system 
occludes atop the Great Lakes.

Normally a stalled frontal boundary during the warm season would 
raise concern with respect to hydrologic concerns, though it seems 
we may escape without too much harm this time around. Nonetheless, 
it's worth noting that parts of Lower Michigan have picked up 1-2" 
of water over the past week which has likely priming the ground for 
runoff should heavy rain occur anytime in the near-future. Out of 
all days this week, Thursday will be the day to watch in terms of 
potential flooding issues should a more substantial convective 
episode materialize.

Next Sunday and Monday look relatively quiet though ensemble model 
guidance suggests a return of precipitation chances by the middle of 
next week. Indeed, we remain in an active spring-time pattern. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1226 AM EDT Mon Apr 15 2019

Light snow showers with occasional drops in visibility to 3SM, 
stratus with cigs around 700-900 ft, and northwesterly wind gusts
to 20 kts will continue through the overnight period with rapidly
improving conditions by sunrise. VFR cigs (with only a few clouds
aob 20000 ft) should be achieved by mid-morning. Mid-level cloud 
cover will increase from west to east toward the end of the TAF 
period as winds become light and variable. 

&&

.MARINE...
Issued at 330 AM EDT Mon Apr 15 2019

Waves will continue to decrease this morning but remain hazardous to 
small crafts through daybreak (except south of South Haven until 
noon). Winds and waves are then expected to remain below 22 kts and 
4 ft, respectively, through at least the middle of next week. 

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 8 AM EDT this morning for LMZ847>849.

     Small Craft Advisory until 2 PM EDT this afternoon for 
     LMZ844>846.

&&

$$

SYNOPSIS...Borchardt
DISCUSSION...Borchardt
AVIATION...Borchardt
MARINE...Borchardt