Area forecast discussion
National Weather Service Grand Rapids Michigan
345 PM EDT Wednesday may 22 2013
Latest update...
synopsis/short term/long term/fireweather/Hydro/marine
Synopsis...
issued at 345 PM EDT Wednesday may 22 2013
Low pressure will slide east through lower Michigan this evening
allowing a cooling...northerly wind to take hold. Showers and storms
will continue into the evening hours before transitioning over to
just showers overnight into Thursday. Additional locally heavy rain
will remain possible through midnight or so. The showers will
gradually taper off from north to south on Thursday as high pressure
builds into the Great Lakes region. The air mass settling in with
the high will be much cooler with highs in the 50s expected Thursday
and 60s for Friday through Sunday. Areas of frost will be possible
Thursday night and Friday night across central lower Michigan
especially. Turning drier and cooler are the main headlines moving
into the latter half of the week and into the Holiday weekend.
&&
Short term...(this evening through Friday night)
issued at 345 PM EDT Wednesday may 22 2013
Main items in the short term are thunderstorm and heavy rain
potential this evening...then chances for frost the next couple of
nights.
At this point expecting continued widespread rain showers
progressing northeast through the forecast area this evening.
Thunder threat remains as well with limited chances for anything
severe. Some heating has occurred though and cannot rule out an
isolated severe storm. Rotational threat looks fairly slim...but
will continue to be monitored by US as storms float north toward the
frontal boundary located over central lower Michigan. Some weak rotation
is still seen even in the storms to the south given bulk shear
values of 30-40 knots. Still the potential for a boost in the
activity between now and 00z as the upper jet streak lift comes into
play.
Convective threat will end and showers will transition to Post
frontal later tonight into Friday as the low and surface cold front
slide east. Have high probability of precipitation both tonight and Thursday morning before
scattering things out during the afternoon.
Threat for frost exists both Thursday night and Friday night as cool
high pressure settles in. Patchy frost is most possible across
central lower Michigan. Some wind may try to hang on in the boundary
layer Thursday night and cirrus may begin spreading in from the
north Friday night. So...at this point thinking more of a frost
potential than a freeze as conditions will not be ideal.
Long term...(saturday through wednesday)
issued at 345 PM EDT Wednesday may 22 2013
The long term continues to look quiet for most of the period with
slowly moderating temperatures. No major changes to the forecast
thinking. We will have to watch some precipitation to our SW for portions of
the weekend...however we believe it will remain dry over the Holiday
weekend. The chance of precipitation will increase late in the period.
The models all continue to indicate that the upper pattern will
nearly take the shape of an Omega block this weekend. This occurs as
the upper system currently impacting our weather will shift to the NE. An
additional short wave will dive south and phase with the NE system
to produce a pretty expansive upper low. This will bottle up the
flow over North America with the upper ridge positioning itself west
of the Great Lakes.
We should stay dry Sat through at least Memorial Day with this upper
air setup. There will be short waves trying to ride over the ridge.
We will have plenty subsidence in place being east of the upper
ridge and a dry low level NE flow around a Hudson Bay high to
keep the area dry. Temperatures look to modify slowly from Sat through
Memorial Day as h850 temperatures warm a degree or two each day.
There is some uncertainty with regards to how quick return flow will
set up on the backside of the eventual migration of the surface ridge to
the east. The GFS is a little quicker than the Euro. That said...the
GFS still has the upper ridge axis over the area on Tuesday. With the
blocky type flow expected and expected slower movement...we will
focus the better precipitation chances toward Wednesday. Temperatures should reach back up
well into the 70s by Wednesday.
&&
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 158 PM EDT Wednesday may 22 2013
Convective trends this afternoon along with lower conditions
expected are the main items of interest with this set of forecasts.
More widespread band of rainfall has lifted to the north of the
terminals early this afternoon. Most of the lower ceilings and visibilities
are located with this rain which is near a warm front lifting
through. Scattered showers and storms are developing south of the
main rain band. These can be expected to be possible through
around 00z or so with the diurnal heating.
The rain band should eventually shift south back into the area
later this evening and overnight as the low pressure shifts east
of the area. We are expecting a good deal of IFR conditions with
this band of rain as it moves back into the area. This rain
should be light...but persist into Thursday afternoon. It will likely
move out after this forecast period.
&&
Marine...
issued at 345 PM EDT Wednesday may 22 2013
Hoisted a Small Craft Advisory for all marine zones from this
evening through Thursday night. Strong north flow to 30 knots is
expected which will build wave heights into the 4 to 7 foot range
into Thursday. Winds and waves will gradually settle down Thursday
night into Friday.
Areas of fog can be expected in the nearshore waters this evening as
warm moist air is in place over the cooler lake water. The north
flow kicks in fairly quick this evening so held off on a marine
dense fog advisory. North flow is already in place from Manistee all
the way south to Muskegon.
&&
Fire weather...
issued at 345 PM EDT Wednesday may 22 2013
Not expecting significant fire weather issue or anything close to
approaching red flag with a moist air mass currently in place
combined with widespread rains of late. In addition...a cooling
trend is expected into the weekend...which will begin late tonight.
Highs Thursday will only be in the 50s...with 60s expected Friday
through Sunday.
&&
Hydrology...
issued at 345 PM EDT Wednesday may 22 2013
Areal Flood Advisory was issued earlier for about the northern half
of the forecast area where heaviest rains have fallen. Croton in
Newaygo County for instance received 2.17 inches from 400 am this
morning through 200 PM this afternoon. Very efficient rainfall
processes ongoing obviously which has been seen in soundings with a
very moist environment in place through a deep layer. Another push
or showers and storms will move through the forecast area this
evening...with Post frontal showers moving through late tonight into
Thursday. Future basin average precipitation tonight and Thursday
should range from a quarter inch in the far southern County Warning Area...to
potentially another half inch or so up north. At this point feel the
current advisory covers things and not expecting the need for
additional Hydro headlines. Significant within bank rises on area
rivers can be expected for basins north of the grand...including the
Muskegon...white...pere Marquette and Chippewa.
&&
GRR watches/warnings/advisories...
Michigan...none.
Lm...Small Craft Advisory from 8 PM this evening to 8 am EDT Friday
for lmz844>849.
&&
$$
Synopsis...Duke
short term...Duke
long term...njj
aviation...njj
fire weather...Duke
hydrology...Duke
marine...Duke
