Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 190957

Area Forecast Discussion
National Weather Service Denver/Boulder CO
357 AM MDT Mon Jun 19 2017

.SHORT TERM...(Today and tonight)
Issued at 358 AM MDT Mon Jun 19 2017

Northwest flow aloft continues across Colorado through tonight.
Currently GOES-16 not showing many clouds across our area other
than the far NE corner of the state. The clouds should hang on
across the NE corner through mid morning before pushing east.
With weak subsidence from the strong ridge to our southwest, skies
today will be mostly sunny. Despite surface dewpoints in the 40s
throughout the day across the Plains, overall moisture is limited
with PWATs 0.5" along and west of I-25 and at best around 0.7"
across the NE Plains of Colorado. Instability is also limited so
expect dry conditions area wide. Temperatures should warm into the
mid 80s Plains and upper 60s to upper 70s across the Mountains,
similar to Sunday`s maximum temperatures.

Tonight quiet weather continues with subsidence and dry northwest
flow aloft and light drainage winds expected across the Denver
metro area. The pressure gradient is weak overnight resulting in
favorable conditions for radiational cooling. Expect lows near 60
across the Denver metro area and nearest the foothills, with 50s
elsewhere below 7000 feet. Low to mid 40s in the mountains and
West Slope.

.LONG TERM...(Tuesday through Sunday)
Issued at 358 AM MDT Mon Jun 19 2017

The center of hot upper ridge over the southern Great Basin is still
progged to shift southward over Arizona and wrn New Mexico by mid-
week, and eventually over the nrn Baja by the weekend. As the upper
high shifts south, the northwesterly flow aloft over nern Colorado
on Tuesday turns zonal on Wednesday and Thursday. This shift in flow
will spread abnormally air aloft over the region resulting in sfc
temperatures as much as 10-14 deg f above average for the date.
Wednesday, the first full day of summer, is likely to be the warmest
day of the week for these parts. FYI, Denver`s average high on the
21st and 22nd is 84 and 85, respectively. The high country won`t
escape the heat with high temps Tuesday-Thursday in the 70s and 80s.

Even with the very warm temps aloft, strong boundary layer diabatic
heating should be adequate to produce isolated to scattered gusty t-
storms over and near the high terrain each afternoon/early evening
through Thursday. Storm coverage looks best on Wednesday with brief
cooling at mid-level with the passage of a weak shortwave late in
the day. By Thursday, the focus for storm development shifts to the
far eastern counties of the CWA in the vicinity of what appears to be
a weak nearly stationary frontal boundary or dryline. In any case,
storm intensities should not be all that great and any precip should
be light and spotty.

Up to this point, models are in reasonably good agreement. Going
forward, however, significant differences in their temp and wind
fields appear. This creates additional uncertainty to the forecast
particularly during the Friday-Saturday time frame. GFS, ECMWF and
Canadian Global models each show a trend back to northwest flow with
a broad upper trough carving out over the northern Great Basins.
However, the GFS shows a strong cold front sliding south thru ern
Colorado on Friday and a relatively deep, moist upslope flow forming
east of the mtns by afternoon. This would account for the
significantly cooler most temperatures and elevated PoPs offered by
this model. Whereas, the European and Canadian models indicate a
much warmer and drier west-southwesterly downslope flow on Friday,
and just of a hint of a dry cold front slipping south thru ern
sections of the CWA on Saturday, sending temps several degs below
average. For now, will go with a blend and trend towards higher PoPs
on Friday and cooler temps both days, but not as cold as the GFS
would have us believe.

For Sunday, should see temps rebounding and precip chances
dropping off as a strong high pressure ridge builds in from the


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 358 AM MDT Mon Jun 19 2017

VFR and no precipitation/convection expected through Tuesday
morning at the TAF sites. High res models and current
observational fields do not seem to indicate drainage winds
developing this morning, so will keep NW surface winds around 10
kts through sunrise then light and variable winds until easterly
diurnal winds kick in between 16-18Z. Tonight drainage winds
should kick in after 05Z.




SHORT TERM...Schlatter
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