Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
349 am MDT Wednesday Apr 23 2014 


Short term...(today through tonight ) 
issued at 317 am MDT Wednesday Apr 23 2014 


Upper level trough will move across the Great Basin this morning and 
into Colorado this afternoon. The trough will continue eastward 
tonight and exit the state by Thursday morning. A surface low will 
deepen over southeast Colorado today. This will cause southerly 
winds over northeast Colorado to turn westerly during the late 
morning hours and then northwest to northerly during the afternoon 
and evening. The northwest winds will pull in cooler air this 
afternoon. Highs will be cooler today...but still slightly above 
normal. Southern Lincoln County will see southwesterly winds for 
much of the afternoon. This will push highs close to 80 degrees. The 
gusty southerly winds and low relative humidities will produce red 
flag conditions. 


Lift ahead of the trough has produced scattered showers a few 
thunderstorms over northwest Colorado early this morning. As the 
trough progresses eastward...so will the chance for showers and 
thunderstorms. Not a lot of moisture with this system...especially 
at the lower levels...so the chance for precipitation will remain 
low 10-40 percent. By midnight...the lift ahead of the trough will 
be east of the state so expect the chance for showers to end by 
then. 


Long term...(thursday through tuesday) 
issued at 317 am MDT Wednesday Apr 23 2014 


Westerly flow aloft will be over the region on Thursday as only some higher level 
moisture moves across. Should see a dry day with afternoon highs in 
the 65 to 70 degree range over northestern Colorado. Gusty west-northwest winds will be 
possible in the afternoon along the Wyoming border and across the far northestern 
plains. 


By Friday the flow aloft will become more west-southwest as a strong upper level 
trough approaches the West Coast. Outside of some middle and high 
clouds will keep the forecast dry through Friday night. Surface low pressure will 
gradually intensify from central Wyoming into central Colorado with gusty south-southeast winds 
developing by afternoon over northestern Colorado. Afternoon highs will be in the 70s over 
northestern Colorado with low humidity values so could see an increase in fire 
danger over the Palmer Divide and portions of the plains. 


For the weekend the medium range models continue to yo-yo their 
forecasts. Two nights ago they were trending towards a strong closed 
low developing over southeastern Colorado by sun while last night and yesterday 
morning they had this low further north over northern co/WY. Tonight 
they are all now trending back towards a southern track with a strong 
upper level low becoming vertically stacked over southeastern Colorado on sun. 
Suffice to say the forecast is still not very clear as to where this 
strong upper level low will end up by sun. 


At any rate ahead of this system on Sat strong surface low pressure will 
intensify over Colorado. At this point considering how much the 
flow will back ahead of the strong upper level trough none of them 
models seem to have a clue with respect to where the main surface low 
will be. With the main upper level low forecast to be over northestern Arizona/northwestern 
nm by Sat evening would think main surface low will hang back closer to 
the foothills and not reside over the eastern plains. As a result this 
should allow for southeasterly inflow of deeper lower level moisture across 
the plains by late afternoon into the evening hours with a potential 
triple point somewhere to the northeast or east of Denver. With 
soundings showing excellent middle level shear and high helicity values 
one would think there would be some potential for severe storms late 
Sat afternoon into Sat night over portions of the northestern plains as main 
upper level trough approaches. Elsewhere with decent lapse rates 
in the mountains and increasing middle level qg ascent by late afternoon should 
see a chance of showers/thunderstorms as well unless system ends up being 
slower that forecast. Meanwhile high temperatures over northestern Colorado may rise back 
into the lower to middle 70s as 850-700 mb temperatures are similar to 
Friday. 


For sun as mentioned above the whole forecast depends on where a strong 
closed low develops. If it does take a more southern Route into southeastern Colorado 
then that would set the stage for a Spring storm over northern Colorado. The 
one thing that is lacking is cold air with this system so precipitation 
across northestern Colorado and most of the foothills would be all rain through Sun 
afternoon with the threat of heavy snow confined to the mountains at this 
time can not ignore the fact that a strong storm system may end up over 
southeastern Colorado so will bump probability of precipitation up into chance category for northestern Colorado/foothills 
and likely for the mountains as for highs will keep readings in the 50s 
over northestern Colorado. 


By Sun night the closed low is forecast to move slowly into western Kansas 
and then into central Kansas by Monday afternoon based on current data. If 
this occurs then significant precipitation could linger into Monday morning over 
northern Colorado before gradually ending by midday Monday. Thus have raised probability of precipitation 
for Sun night across the County Warning Area. Temperatures will become colder Sun night so 
precipitation should become all snow in the foothills and over the Palmer 
Divide with a rain/snow mix possible over northestern Colorado after midnight. 
As for highs on Monday will keep readings mostly in the 50s over northestern 
Colorado. 


For Monday night into Tuesday the upper level storm system will move into 
the middle Mississippi Valley region. However there are some differences 
between the European model (ecmwf) and GFS as the European model (ecmwf) shows a secondary trough 
moving across Monday night in northwest flow aloft along with a strong cold front 
which leads to another shot of precipitation Monday night into Tuesday morning. 
Meanwhile the GFS does not show this secondary trough and has much 
drier air over the area. For now will just mention some low probability of precipitation 
for Monday night but keep forecast mainly dry for Tuesday. Meanwhile highs on 
Tuesday based on the European model (ecmwf) would stay in the 50s while the GFS has 
readings in the 60s. At this time will trend with the European model (ecmwf) and 
keep readings in the 50s. 


&& 


Aviation...(for the tafs through 12z Thursday morning) issued at 
317 am MDT Wednesday Apr 23 2014 


Southerly winds will prevail across the Denver area this morning. 
Winds will turn west between 16 and 19z and then northwesterly after 
as S surface low strengthens over southeast Colorado. Winds speeds 
will generally be 10-25 knots. Though could be a little stronger 
around 00z and near showers. Isolated showers will be possible from 
17z-04z. Can not rule out a brief and weak thunderstorm...however 
expect thunderstorms to stay east of the Denver area. 


&& 


Bou watches/warnings/advisories... 
red flag warning from noon today to 8 PM MDT this evening for 
coz247. 


&& 


$$ 


Short term...meier 
long term...rpk 
aviation...meier 






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