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fxus63 kgrr 191117 
afdgrr

Area forecast discussion
National Weather Service Grand Rapids Michigan
717 am EDT Thu Sep 19 2019

Latest update...
aviation

Synopsis...
issued at 250 am EDT Thu Sep 19 2019

- warmer than normal temperatures expected through Monday.

- Storms expected late Saturday and sunday; heavy rain possible.

&&

Discussion...(today through next wednesday)
issued at 250 am EDT Thu Sep 19 2019

The overall forecast hasn't changed much. Main concerns deal with
the heavy rain potential late Saturday into Sunday.

Very warm weather is expected today and Friday. Michigan will remain
under a large upper ridge through early Saturday before a strong
short wave moving across the plains will nudge it eastward. The
warmth under the ridge will translate to surface highs in the mid
80s today and tomorrow. Humid conditions will return Friday
afternoon when dewpoints climb above 60. Humid conditions will
continue through Sunday at which point a cold front will move
through and dry things out a bit.

A strong llj will draw moisture northward and precipitable water
amounts are progd to climb to near 2 inches late Saturday. There is
some disagreement between the GFS and the slower European model (ecmwf) wrt frontal
timing. The Euro holds the front back until after midnight Saturday
night. The GFS on the other hand shows pcpn arriving on the Lake
Shore by 00z Sunday and seems too quick compared to the
ECMWF/NAM/CMC.

The western County Warning Area will have the highest chance at showers/storms
Saturday night with the rest of the cwa seeing rain Sunday. This
front doesn't look like a fast mover and so heavy rain seems like a
possibility. Some locations may see over 2 inches of rain Saturday
night/Sunday. Shear values increase to 40 kts Sunday which normally
would be a concern for strong storms, however instability appears to
be a limiting factor.

The front should clear the cwa Sunday night and the rest of the
period will see highs fall back to around 70 and dewpoints fall into
the 50s.

&&

Aviation...(for the 12z tafs through 12z Friday morning)
issued at 717 am EDT Thu Sep 19 2019

Thanks to upper level ridging and a surface high moving off the
East Coast but with surface ridge back to southwest Michigan,
skies will for the most part stay clear below 20,000 ft today.
The thunderstorms over WI and Upper Michigan may make it into
northern lower Michigan but will likely get no where close to the
southwest Michigan taf sites.

Winds will be light from the southeast today but mkg and likely
GRR will see the winds turn to the southwest due to the lake
breeze. Of course tonight winds go back to easterly.




&&

Marine...
issued at 250 am EDT Thu Sep 19 2019

Light southeast wind expected today resulting in waves around a
foot.



&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

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