Remarks on the forecast - Today and Tonight

A weak low pressure system that tracked through northern Michigan Thursday is forcing a weak cold
front through se Michigan at press time. Looking aloft, heights are lowering as a mid level trough
works eastward with a lobe of vorticity pivoting through lower Michigan. The trough is fracturing in
the sense that an upper low that has been clinging to the base of the trough finally cuts off over
the deep south. A shortwave seen on water vapor over the plains is shearing apart as it lifts over
the area leading to a midlevel cloud field. Models continue to advertise an uptick in frontogenesis
right over se Michigan this morning from about 09-12z as the 500mb height fall maximum flares up
over the area inducing the jet to strengthen with the right entrance region also over the area. So
model wise the upper levels look favorable for some precip this morning with some aide in the low
level fgen. A big downfall to the system will be with moisture. The DTX 00z sounding shows only a
half inch of precipitable water in the column with a deep layer of dry air up to about 9Kft. Models
are right on track with this and do up the precipitable waters to around .7 during the fropa.
Upstream obs are good for showing the very scattered nature of the precip thus far with a few obs
showing light rain or drizzle with cigs lowering from 10Kft to around 6500Ft with the precip. The
struggles with dry bl air should continue and have been thus far as radar returns have been showing
up for hours with nothing to show for it. But as mentioned, the models show the strongest forcing
developing right over head as the upper level players come together so will continue a band of
chance PoP working through the area during the morning hours. QPF will remain low due to the lack of
moisture present to work with.

The rest of the day will show an improving trend as ridging will quickly fill in behind the front.
The longwave pattern is low amplitude leading to only a small drop off in temperatures behind the
front. The sfc high will pass to the north so we should keep a semblance of easterly flow as winds
relax overnight. Skies will also be clearing which will favor some radiative cooling processes.
Dewpoints will only fall into the upper 20s to low 30s which will cap off the temperature drop
overnight.

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Remaining Forecast opinion - Saturday through next Thursday

Quiet weather is expected over the weekend as high pressure builds southeast across the area.
Temperatures will be cool Saturday under the influence of this high, but moderate within return
southwest flow on the backside of this system on Sunday, pushing 70F in some instances.

Mild weather will persist into Monday night/early Tuesday as low pressure approaches from the
Central Plains. This low will develop as the lead impulse in a string of northern Pacific shortwaves
phases with southern stream shortwave now meandering east towards Baja California. As this system
encroaches, rain showers will become more prevalent from Sunday night into Monday and peak in
coverage/intensity Monday night with the passage of the system.

While some colder polar air is pulled south into the area behind this system, the upper level flow
remains zonal, so significant cooling will be held at Bay with temperatures returning to the 60s by
late week.

After another period of relatively quiet weather during the middle of the week, the chance of rain
showers increases again late in the forecast period as the next significant surge of Pacific
shortwave energy arrives in the vicinity. This system appears to have a better chance at phasing
with the polar jet stream over southern Canada and will most likely be a stronger system than the
initial low earlier in the week. While precipitation will remain rain, notably colder air will
filter back into the area just beyond this forecast period.

. . posted at 323 AM EDT Friday April 18 2014


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