457
FXUS63 KGRR 122346
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
746 PM EDT Mon Apr 12 2021

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Mon Apr 12 2021

- Overall a cool pattern for the next 7 days

- Chances for showers mid week

- Another small chance for showers early next week

&&

.DISCUSSION...(This evening through next Monday)
Issued at 330 PM EDT Mon Apr 12 2021

-- Overall a cool pattern for the next 7 days --

850mb temperatures much of the next 7 days are actually
negative/below zero C. This should yield temperatures that are at
the very least near normals and more likely below normals for this
time of year. Normals highs are in the mid to upper 50s with lows
in the 30s. Highs on Wednesday will likely hold in the 40s in many
areas. Low temperatures Thursday morning and Friday morning will
likely be near the freezing mark around 32F. Certainly no big warm
up is noted in the next 7 days.

-- Chances for showers mid week --

We look to stay mainly dry tonight and Tuesday as we will be in
between upper lows traversing the region. Tuesday night the upper
low that is located upstream begins to move into the Great Lakes.
The upper low is then overhead Tuesday night through Wednesday
night and does not fully leave the area until into Friday. So we
are looking at a fair amount of clouds the rest of the week. Best
chances for precipitation will come Wednesday and Wednesday night
with the upper low overhead. Precipitation will likely mix with
some wet snow at times Tuesday night and Wednesday night with no
accumulation expected. Our chances for precipitation are overall
quite low 20-30 percent, but could see this needing to be bumped
up a tad Wednesday and Wednesday night. The latter half of the
work week looks to be fairly quiet as we go into a baggy pattern
at the surface and somewhat of a col aloft.

-- Another small chance for showers early next week --

Another chance for showers creeps up early next week as there
appears to be shortwaves moving through the area. Timing
differences exist between the operational ECMWF and GFS. At this
point our blend has a dry forecast from Sunday into early next
week but we may be adding chances for some shower if models
converge on a better shortwave moving through the area. ECMWF has
-5C 850mb temps next Monday afternoon, so the cool weather continues.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 746 PM EDT Mon Apr 12 2021

VFR conditions will prevail tonight into Tuesday with SCT-BKN
stratocumulus clouds around 5000 ft. West-southwest sfc winds
will relax after sunset to 5-10 kts, but they`ll become gusty
again by mid-morning Tuesday with frequent gusts to 20-25 kts
Tuesday afternoon.

&&

.MARINE...
Issued at 330 PM EDT Mon Apr 12 2021

Winds on Lake Michigan will be westerly much of the time from
tonight through Wednesday. Wind speeds will generally by in the
10-20 knot range so we are expecting wave heights in the 1-3 foot
range.

Winds and waves will ramp up Wednesday night into Thursday though
in cold air advection on the back side of the upper low. We are
most likely looking at northwest winds of 20-30 knots which will
produce waves of 3-6 feet. A Small Craft Advisory will likely be
needed but it is a bit early to do that just yet.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Duke
DISCUSSION...Duke
AVIATION...Meade
MARINE...Duke

NWS GRR Office Area Forecast Discussion