Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Denver/Boulder Colorado
426 am MDT Friday Oct 31 2014

Short term...(today through tonight )
issued at 426 am MDT Friday Oct 31 2014

A sharp upper level ridge over Colorado will deliver another dry
and mostly sunny day for the end of the month. Some high level
moisture will slip over the ridge and produce cirrus clouds at
times this afternoon and tonight. Another thing to look out for
is some patchy low clouds and fog developing over the northeast
corner of the state around sunrise. Satellite imagery has been
showing an area of stratus moving southwestward from central
Nebraska all night...which should reach Sedgwick and Phillips
counties by 6 am. Dew point depressions elsewhere on the northeast
plains are down to 3 degrees or we may see additional
areas of stratus or fog develop over the next couple hours. If
stratus develops in the South Platte valley between Fort Morgan
and Greeley...then it may get drawn into the northern Denver metropolitan
area for a few hours this morning.

Southerly winds over the Palmer Divide are also expected to
increase through the day as high pressure building over Nebraska
and Kansas tightens the pressure gradient across eastern Colorado.
The southerly winds should also induce a Denver cyclone which will
keep advecting cool air from the Great Plains towards the
foothills which will keep the afternoon highs cooler than previous
days. High temperatures should end up right around seasonal
normals for this time of year.

Outdoor activities this evening should see no impact from the
weather as temperatures cool from afternoon highs in the upper 50s
to late evening readings in the lower to middle 40s.

Long term...(saturday through thursday)
issued at 426 am MDT Friday Oct 31 2014

An upper level trough will be over the western US on Sat as the upper
level ridge shifts eastward. This leaves northern Colorado in southwesterly flow aloft
with some increase in middle level moisture in the mountains by afternoon. With
decent lapse rates over the higher terrain there will be a slight
chance of showers mainly west of The Divide. Over northestern Colorado it will be
dry with a surface Lee trough over the plains. Thus should see warmer
temperatures across the plains with readings ranging from the middle to upper
60s over the far northestern corner with lower 70s along the Front Range.

On sun the upper level trough over the western US will split as one
piece of energy lifts north-northeast across the northern rockies while a second
piece of energy moves into the Great Basin. This will leave northern Colorado
in southwesterly flow aloft with an increase in moisture over the mountains
favorable lapse rates along with some minor middle level ascent by afternoon
will lead to a chance of showers in the mountains and highr valleys. Over
northestern Colorado there will be an increase in middle level clouds with possibly
a slight chance of -shra near the Wyoming border by late afternoon. As for highs
increasing cloud cover combined with slight cooling in the 850-700
mb layer will keep highs in the middle to upper 60s across northestern Colorado.

For Sun night into Monday the European model (ecmwf) and GFS show the upper level trough
over the Great Basin moving eastward across the area. Combination
of middle level ascent and favorable lapse rates should lead to a good
chance of precipitation in the mountains and higher valleys. Orographics are weak through
the period so snow amounts in the mountains will probably stay generally
on the light side although some places could receive advisory
amounts. Over northestern Colorado a cold fnt will move across the plains late
Sun night into Monday morning with upslope flow to around 700 mb based
on current GFS. As main upper level trough and associated middle level
ascent move across on Monday one would think there would be a good chance
of precipitation in and near the foothills and possibly across the plains as
well. Soundings from the European model (ecmwf) would have precipitation falling mostly as snow
along the Front Range on Monday while the GFS is warmer and keeps precipitation
mostly rain. As for highs on Monday will keep readings in the 45 to 50
degree range over northestern Colorado although it could be colder if European model (ecmwf) is

By Monday night the upper level trough will gradually move east of the
area with precipitation ending early Monday evening in most areas. By Tuesday drier
air in northwest flow aloft will be over the area so will not mention any
precipitation. Will keep highs in the 50s over northestern Colorado.

For Wednesday and Thursday a flat upper level ridge will be over the area with
dry conditions both days. 850-700 mb temperatures rise another 5 degees on
Wednesday and then a few more degrees on Thursday. Thus highs should rise back
into the lower to middle 60s over northestern Colorado on Wednesday and then from 65 to 70
on Thursday.


Aviation...(for the tafs through 12z Saturday morning)
issued at 426 am MDT Friday Oct 31 2014

Winds this morning have been oscillating between drainage
southerlies and easterlies as a Denver cyclone tries to develop.
Later today should see the winds swing around to the east and
northeast...and then northwest as the cyclone matures by early
afternoon. Dew point depressions in the Denver area are currently
large enough that low clouds should not develop. However...cooler
and moister air is not too far the South Platte River
Valley from between Greeley and Fort Morgan eastward. There is a
chance that patchy fog or stratus could develop in the River
Valley and then move into kden for a few hours. Will keep the
mention of vcfg in the next taf issuance. aviation
impacts are expected through the next 24 hours.


Bou watches/warnings/advisories...


Short term...dankers
long term...rpk

National Weather Service Glossary of Abbreviations