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Displaying AFOS PIL: AFDDTX Received: 2018-04-25 19:21 UTC

FXUS63 KDTX 251921

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
321 PM EDT Wed Apr 25 2018


Partial clearing across the southern Metro region have allowed 
temperatures to overachieve this afternoon as temperatures have 
climbed into the lower 60s. Northerly flow off of Lake Huron have 
kept temperatures capped in the 40s across the Thumb, while more 
moderate temperatures have been observed from Pontiac up to Saginaw, 
with highs in the 50s. Communities in the thumb, especially closer 
to the shoreline, will have a slight chance to see brief showers 
through the evening as a PV anomaly resides across central Lake 
Huron. Cloud cover associated with this eastward moving PV anomaly 
and diurnal heating will begin to diminish tonight and overnight as 
incoming subsidence and dry air settles in across SE MI. Winds 
gusting between 15 - 20 mph, isolated 25 mph, will also quickly 
diminish tonight after diurnal mixing ceases after sunset. The cut-
off low and associated PV anomaly will push over New York by 
Thursday 12Z and will continue to reinforce NW flow across Michigan, 
allowing 850 mb temperatures to drop to an average of 1C overnight. 
Clear skies will allow for strong radiational cooling overnight, 
supporting lows in the lower 30s across SE MI and mid-30s across the 
urban Metro region. A very slight chance for periods of patchy fog 
to develop overnight across the Thumb, as winds diminish and dry air 
moves in aloft, however, opted to leave patchy fog out of the 
official forecast as latest high-resolution runs keep surface 
conditions too dry to support fog chances. 

Otherwise, a ridge of high pressure will then build across Michigan 
throughout Thursday and will continue to keep conditions dry as 
clear to partly clouds skies persist throughout the day. Copious 
amount of sunshine will allow temperatures to push into the low to 
mid-60s for a daytime high as a weak pressure gradient keep winds 
calm to light. 

The next chance for rain will enter late Friday morning into the 
early afternoon as an upper-level trough and associated cold front 
push through the Great Lakes region. Temperatures will remain below-
normal as a thermal trough and overcast conditions help cap daytime 
highs to the mid to upper 50s Friday afternoon. For reference, 
normal highs reside in the lower-60s for late April. Otherwise, a 
brief lull in precipitation will be possible late Friday afternoon, 
before an embedded shortwave located on the backside of a trough 
coupled with left exit dynamics from a jet maxima aloft help support 
a second round of showers. Rain chances will be centered across the 
Metro region, late Friday into Saturday morning.

Any lingering showers will be on the way out by Saturday afternoon 
as upper jet support and shortwave move off to the east. Strong 
ridging through the troposphere will take over in the wake and high 
pressure at the surface will dominate the weekend forecast. Thermal 
trough with 850 mb temps in the negative single digits C will linger 
through Saturday and limit surface highs to the low 50s. Quick 
modification of this air mass in late April insolation will allow 
Sunday's highs to rise to the mid 50s. Dry and mostly sunny 
conditions will prevail Saturday through late Tuesday as the high 
pressure slowly drifts south and east. Warm air advection will 
become established by Monday with southerly flow bringing highs to 
the upper 60s that day, and the lower 70s by midweek. Chance for 
rain returns on Wednesday due to low pressure over Ontario pushing a 
cold front through the Great Lakes.



Small craft advisories remain in effect for Saginaw Bay and southern 
Lake Huron through this evening. Peak gusts topping out near 25 
knots will relax through the evening as low pressure tracks east to 
southern Ontario but the long north fetch will keep waves elevated 
in excess of 4 feet for several more hours. High pressure will build 
overhead tonight and hold through Thursday resulting in light winds 
backing from northwest to southwest. A cold front will then reach 
northern Lake Huron late Thursday night and sweep across the rest of 
the basin through the day Friday. This combined with an additional 
low pressure system sweeping across the southern lakes will keep 
unsettled conditions and gusty northerly flow through the weekend.


Issued at 112 PM EDT Wed Apr 25 2018 


Low pressure will track down the axis of Lake Huron through the 
afternoon which will keep MVFR CIGS around into the evening. 
Meanwhile, dry air over the western side of the state will be 
encroaching through that time helping to scatter out the clouds from 
west to east. The terminals look to fall near the western edge of 
the thicker clouds which could lead to brief fluctuations into VFR 
over the course of the late afternoon. Skies will clear and winds 
will become light tonight as high pressure builds into the region. 
Still some signals that a brief period of shallow MVFR could develop 
as nocturnal min temps are reached toward morning. 

For DTW... Wind direction stays consistent from the NNW in the 10 to 
15 knot range and likely requires NE traffic flow operations. Winds 
will drop off while becoming more westerly around midnight allowing 
more favorable SW flow operations. 


* High for ceiling 5000 ft or less into this evening.


Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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