Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 181602
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1002 AM MDT WED MAY 18 2016

.UPDATE...
Issued at 1000 AM MDT Wed May 18 2016

Patchy dense fog along the I-25 corridor N-NW of Denver and in
the Broomfield to Erie area has pretty much dissipated. The narrow
north-south band of stratus handing over the corridor also continues
to erode. Elsewhere...low to mid clouds continue to hang on over
mountain areas generally west of the Continental Divide...South
Park...as well as Elbert and Lincoln Counties along the Palmer
Divide. Skies on the plains for the most part were clear this
morning.

Later today...still counting on convection to initiate first over
the high terrain within the deeper moisture presently along and
south of the I-70 corridor by late this morning. Further warming
coupled with the passage of weak mid-level disturbance embedded in
northwest flow is expected to fuel shower and t-storm formation
over the northern mtn ranges not too long after that. Probability
of showers and t-storms in the high country this afternoon put at
40-60 percent...once again with the higher odds south of I-70. On
the plains...model soundings and sfc/boundary layer stability plots
indicate strong cin at the present time. Models show this cin
eroding and sfc based capes in the 300-600 j/kg range along the
higher fringes such as over the Palmer Divide...Cheyenne Ridge and
near the foothills after 20z. HRRR and NAM also indicate a finger
of 400-650 cape reaching northward along an axis from Castle Rock
to just east of Denver International Airport and essentially no
CIN by 21z. And with a favorable sely bndry layer flow...this too
could be an area of t-storm formation later today. However...the
potential for severe weather appears low. Changes to the forecast
grids will include this possibility. Otherwise the chance of
showers/t-storm farther out on the plains less than 10 percent.

&&

.SHORT TERM...(Today and tonight)
Issued at 248 AM MDT Wed May 18 2016

A weak upper level low over AZ will move into NM by tonight.  Over
nrn CO the flow aloft will be weak however there still will be quite
a bit of lingering moisture across the area.  Aftn capes across the
higher terrain and in and nr the foothills will range fm 500-700
j/kg so expect a chance of showers and storms across the higher
terrain with only wdly sct activity along the front range.  Highs
this aftn will be warmer across the plains with readings in the
upper 50s to mid 60s.

For tonight will continue to see a chc of showers and a few storms
early in the evening across the higher terrain but most activity
should end before midnight.

.LONG TERM...(Thursday through Tuesday)
Issued at 248 AM MDT Wed May 18 2016

Models have very weak northerly flow aloft for the CWA on
Thursday. By late day, continuing well into Friday night...models
have and upper ridge over the forecast area. The flow aloft at 12Z
Saturday morning is weak and southwesterly. The QG Omega fields
show benign synoptic scale energy for the CWA through Friday
night. The boundary layer flow is mainly southeasterly during the
days with normal south-southwesterly drainage at night time. For
moisture, there is some around, certainly some late day/evening
convective cloudiness. Precipitable water values are progged in
the 0.30 to 0.60 inch range Thursday and Thursday night...then the
0.35 to 0.90 inch range Friday and Friday night. There is some
CAPE over the CWA late day Thursday, with the higher values over
the high county. The CAPE is more widespread with higher values
late day Friday. Lapse rates are fairly steep over the mountains
late day Thursday, but no so over the eastern plains. Friday`s
late day lapse rates are pretty steep for all the CWA. Dew point
readings are mainly in the 30s F mountains and 40s F plains
Thursday and Thursday night. Same on Friday, but there are some
50s F readings over the far eastern plains. For pops...will go
with 40%s in the mountains, down to 10%s over the far east both
late day periods for convective showers and thunderstorms. For
temperatures, Thursday`s highs look to be 3-5 C warmer than
today`s highs. Friday`s highs are 2-4 C warmer than Thursday`s.
For the later days, Saturday through Tuesday, models have
southwesterly flow aloft for the CWA on Saturday and Sunday with a
strong upper trough/closed low over the west coast and Great
basin. By Sunday night...one piece of the trough moves across
Colorado. On Monday and Tuesday...west-southwesterly flow aloft
is in place...with another upper trough over the West Coast.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 1000 AM MDT Wed May 18 2016

Scattered low stratus type clouds expected to burn off in the
next hour...but should then see redevelopment of convective
clouds not too long after that once the convective temperature
around 56 degs is reached. Rain chances are low today...although
there is a slight chance that a line of weak t-storms will form
south and east of KDEN and KAPA after 20z today. Severe weather
potential appears low...although brief light rain shower...gusty
outflow winds and cg lightning will be possible. Most if not all
of this activity should settle down by sunset. South-southeast
winds of 8-15kts will be common at KAPA and KDEN today and
tonight. Light and variable winds at KBJC may briefly become
southeasterly at 5-8kts in the afternoon.

&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

UPDATE...Baker
SHORT TERM...RPK
LONG TERM...RJK
AVIATION...Baker



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