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fxus63 klbf 181244 
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Area forecast discussion 
National Weather Service North Platte NE 
740 am CDT Friday Jul 18 2008 


Update... 
convective system moving across the South Dakota-Nebraska border 
is pretty persistent. As a result...we are updating precipitation 
probabilities to increase them this morning. 
&& 


Previous discussion... 
convection seemed to have pushed through County Warning Area quicker than expected 
24 hours ago and again strong and widespread convection seems to 
have pushed it well into Kansas with surface low over southeast Colorado at this time. Fast 
zonal flow continue over northern rockies/plains and cyclogenesis is 
commencing over S.Wyoming rockies at this time and there seems to be a secondary 
boundary forming across northern County Warning Area this morning according to surface 
analysis with both wind and some moisture convergence. Heavy rain 
did affect southern and eastern County Warning Area in flash flood advisory area with estimates of 
near 5 inches in places. Quick glance at local stream data shows 
everything is in check this morning with medium creek showing the most 
response but on the way down...with clear radar at this time and expected 
heavy rainfall outside of County Warning Area will end flash flood advisory at issuance. Hard to get 
a complete handle of forecast with models struggling with convection and 
will base much of early forecast on Sat/radar trends. As for temperatures 
easterly flow and saturated ground would seem to indicate that 
numbers should lean to cooler side of guidance over southern/eastern 
County Warning Area at least today and plan to head that way. Far SW Nebraska seems to 
had escaped any precipitation lately and this may be the exception. Would 
expect with southeast/east flow in place that western County Warning Area will be 
under the gun late this afternoon and evening as steep middle level 
lapse rates move over this favorable low level sheared environment in the 
High Plains. Expect thunderstorms and rain will fire in the higher terrain and move 
into western County Warning Area through the late afternoon an evening hours and 
have probability of precipitation included for this. Both models indicating mesoscale convective system may try and 
from over Black Hills region and corfidi vect would take this into 
northern/east County Warning Area late if it hold together so early morning probability of precipitation 
continue for this scenario. Think with Kansas boundary so far south at this time 
that main convection concern will be well southeast of County Warning Area...but then again 
my forecast for that front today was way off. Day shift can monitor 
progress of an northward movement...especially with any cyclogenesis 
over Colorado plains...and add probability of precipitation to SW later...but for now have kept 
fairly small probability of precipitation. Seems to be a front meandering near the northern 
border next few days while upper ridge begins to settle ovhd. Middle 
level temperatures increase to 16c across southern County Warning Area...not unbreakable 
but should limit chances across the south with ring of fire mainly 
being pushed into Dakotas. Should begin to temperatures really rise with 
some guidance already hitting triple digits by Sunday. Have kept 
tempered at this time but trended up slightly...especially in dry SW and 
this can be re-evaluated by later shifts. 


&& 


Aviation discussion... 
low level moisture forecasts indicate that some instrument 
flight conditions will set in by daybreak today...especially in 
western and southwest Nebraska where the thunderstorms overnight 
moistened the boundary layer. With only light east to southeast 
wind...the chances are about even for fog or stratus. Indications 
are that similar conditions can be expected Saturday morning. The 
low level moisture in north central Nebraska do not indicate that 
Valentine will have instrument conditions. 
Also...persistence of a low level boundary across the Central 
Plains may generate thunderstorms again this afternoon and tonight 
in south central and southwest Nebraska. It appears that North 
Platte will be on the northernmost extent of the storms. For now 
then...we will not have a mention of storms in the North Platte or 
Valentine terminal forecasts. 


&& 


Lbf watches/warnings/advisories...none. 


&& 


$$ 


13/Springer