Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
100 PM EDT Wednesday Jun 19 2013 




Aviation... 


//discussion... 


High pressure over Lake Huron will slide into the eastern Great 
Lakes tomorrow...but the influence of this high will 
persist...allowing for clear/mainly clear skies and light winds into 
tomorrow. 


//Dtw threshold threats... 


* none 


&& 


Previous discussion...issued 339 am EDT Wednesday Jun 19 2013 


Short term...today and tonight 


Sprawling high pressure system extending from the upper MS valley to 
western Quebec will maintain control across the region over the next 
24 hours. This will retain a seasonably cooler and more stable 
environment as weak low level easterly flow tucked beneath broad middle 
level northwesterlies limit the diurnal recovery to simple diabatic 
heating provided by strong middle June sunshine. This will translate 
into highs of lower to middle 70s...again slightly cooler along The 
Thumb with the onshore wind off the cooler waters cutting slightly 
into the thermal response. A clear sky...weakening gradient and 
dry profile will again promote good radiational cooling. Coldest 
locales again dipping into the 40s. 


Long term...Thursday through Tuesday 


The upper pattern across the northern United States will deamplify 
over the next couple of days as the large Pacific northwest low shifts inland 
and embedded middle-level impulses trigger episodic convection across 
the northern plains. The simultaneous eastward migration and 
dampening of the downstream ridge over the central Continental U.S. Will force 
Canadian high pressure to exit to the east and force southerly 
return flow to spread into the lower peninsula beginning on 
Thursday. A noteworthy moderation of temperatures will be the result 
as daytime highs rise to 80 for Thursday and solidly into the 
middle-80s on Friday, particularly for western portions of the County Warning Area away 
from potential Lake Shadow impacts. 


A significant transition in the local weather will then commence from 
Saturday Onward as middle-level westerlies emerge across the 
northern tier in response to the collapse of the middle-level ridge. 
This will allow a moist and humid airmass to spill into the region 
which should have no problem yielding high temperatures near 90 
degrees along with upper 60s/low 70s dewpoints. Given southeast 
Michigan's prognosticated favorable location along the instability 
gradient and nose of the veering low-level jet on Saturday, have 
no argument with the ecmwf's suggestion of a convective complex 
impacting the area on Sat, particularly given the excellent 
continuity observed in recent cycles. With this in mind, leaned 
heavily toward a conservative high temperature forecast, around 80 
degrees, for Saturday. 


The Reservoir of instability and associated severe potential will 
continue to build Sunday into Tuesday as a robust zonally-oriented 
eml ribbon becomes increasingly well-established across the Great 
Lakes. Per the usual, this will also introduce Stout middle-level 
capping as evidenced by 00z European model (ecmwf) 850mb temperatures exceeding 20c by 00z 
Monday evening. As a result, both hot temperatures and severe 
convective potential will be in play for Southeast Michigan from 
Sunday Onward. Also Worth noting is that moist boundary layer 
conditions will limit overnight lows to the 70s. 


Marine... 


Canadian high pressure will maintain control across the region 
through Thursday. This will provide a stretch of favorable 
marine conditions through the end of the week. 


&& 


DTX watches/warnings/advisories... 
Michigan...none. 
Lake Huron...none. 
Lake St Clair...none. 
Michigan waters of Lake Erie...none. 


&& 


$$ 


Aviation.....Sf 
short term...mr 
long term....jvc 
marine.......mr 




You can obtain your latest National Weather Service forecasts online 
at www.Weather.Gov/Detroit (all lower case).