Scientific Forecaster Discussion

NWS Discussion
			
				

Area forecast discussion 
National Weather Service Grand Rapids Michigan 
327 am EDT Friday may 24 2013 


Latest update... 
synopsis/short term/long term/fire weather/Hydro/marine 


Synopsis... 
issued at 327 am EDT Friday may 24 2013 


A cool and dry air mass will sit over the Great Lakes region today 
and through the Holiday weekend. Despite this there will be periods 
of clouds moving through. Much of southwest Michigan will see 
increasing clouds tonight. Most of these clouds should erode on 
Saturday...however the far southwest portion of the state may see a 
fair amount of clouds both Saturday and Sunday. A few sprinkles are 
possible Saturday afternoon and evening over the extreme southwest 
portion of the state. Temperatures will be slightly cooler than 
normal through Sunday with daytime highs mainly in the 60s. 


Looking into next week...a chance of rain returns Monday night into 
Tuesday...with another chance of rain by Thursday. Temperatures 
will warm into the 70s for Monday and Tuesday...and 80 to 85 for 
Wednesday and Thursday. 


&& 


Short term...(today through sunday) 
issued at 327 am EDT Friday may 24 2013 


A cool and dry air mass has been ushered into the County Warning Area. Northwest 
flow aloft will keep US from warming up too much over the next 
couple of days. Frost will be possible again tonight and Saturday 
night across central lower. 


Surface high pressure will settle over the region tonight and will 
only drift slowly east to Lake Huron by Sunday. This system will 
keep US slightly cooler than normal along with dry weather. However 
there is more of a concern for more cloud cover over the weekend 
even though the surface high sits over US. 


The upper pattern remains fairly static through the weekend with 
an Omega block in place across the nation. An upper low will remain 
over the Pacific northwest with upper ridging over the middle of the 
nation. The models continue to show moisture from the Pacific 
northwest system coming over the ridge and slipping into the Great 
Lakes region. This appears to arrive by tonight...especially over 
the SW County Warning Area. But it appears there could be enough clouds even in the 
north to not jump on a frost advisory just yet. Will let the day 
shift monitor cloud trends. 


A tough cloud forecast for Saturday and Sunday. Will trend a bit 
cloudier than the previous forecast...but it does appear drier middle 
level air tries to move in from central Canada which may bump the 
clouds a bit further SW. Will carry the most clouds over the SW County Warning Area 
where a sprinkle could even occur Saturday afternoon/evening. Will 
go partly to mostly sunny elsewhere through the weekend. 


Long term...(sunday night through thursday) 
issued at 327 am EDT Friday may 24 2013 


Timing of convection with the warm front lifting through lower 
Michigan early next week is the primary forecast problem in the 
extended. Model agreement is generally good...showing a series of 
convective clusters passing just south of lower Michigan Sunday 
night through Monday night. GFS is quicker to bring the front 
through the forecast area on Monday night...while the ecwmf has it 
very slowly lifting through between Tuesday and Wednesday. 


Perhaps the effect of convection training along the front will 
impede its northward progress...so will shade probability of precipitation higher Tuesday 
night and then focus the higher probability of precipitation across the northern forecast 
area after Wednesday as the front moves north. European model (ecmwf) still shows 
potential for convection through Thursday while the GFS has the 
front well north and upper ridging across lower Michigan. Went with 
slight chance probability of precipitation for now. 


Overall it looks like a potentially wet pattern...and the probability of precipitation could 
be underdone as a result of lack of confidence in timing and 
coverage of precipitation most of the period. 


&& 


Aviation...(for the 06z tafs through 06z Friday night) 
issued at 1158 PM EDT Thursday may 23 2013 


MVFR ceilings have been slow to clear south and east of GRR... but 
satellite trends suggest that VFR will work into all areas by 
06-08z. VFR is likely on Friday into Friday night with north surface 
winds around 10 kts. 


&& 


Marine... 
issued at 327 am EDT Friday may 24 2013 


Winds and waves will gradually diminish this morning as high 
pressure builds in. Small Craft Advisory will be carried through noon today over the 
southern portion of the lake. Thereafter northerly winds will 
continue but will remain 15 knots or less through the weekend. 


&& 


Fire weather... 
issued at 327 am EDT Friday may 24 2013 


A much drier air mass has moved into the region. Daytime relative humidity values 
will drop into the 25 to 30 percent range today through Sunday. 
However northerly winds will stay 15 miles per hour or less through the same 
time period. 


&& 


Hydrology... 
issued at 327 am EDT Friday may 24 2013 


A dry spell is in store for the region. The next decent chance of 
rain should hold off until Monday night. High River levels will 
slowly subside into early next week. 


&& 


GRR watches/warnings/advisories... 
Michigan...frost advisory until 7 am EDT this morning for miz037>040- 
043>046-050>052-056>059. 


Lm...Small Craft Advisory until 7 am EDT this morning for lmz846>849. 


Small Craft Advisory until noon EDT today for lmz844-845. 


&& 


$$ 


Synopsis...jk 
short term...jk 
long term...ostuno 
aviation...Meade 
fire weather...jk 
hydrology...jk 
marine...jk