Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 272025

Area Forecast Discussion
National Weather Service North Platte NE
325 PM CDT Tue Sep 27 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 323 PM CDT Tue Sep 27 2016

The main forecast challenge over the short term (through
Wednesday afternoon) deals with temperatures. A weak cold front
drops southwest across the forecast area early Wednesday.

This evening... clear skies continue with very dry air in place, as
told by 40F+ sfc dew point depressions and PWAT around 0.5" as shown
by the RAP. West/northwest downsloping flow at 850hpa will help with
further drying, but will gradually transition to due north by 06z.

Overnight... the westward advancement of the cold front is evident
at 850hpa as north central Neb cools from 15C to 7C and KLBF from
19C to 13C by the morning. With lightening sfc winds, a clear sky,
and low level CAA, trended min temps toward the cooler MAV solution
and dropped another degree in the river valleys.

Wednesday... western Nebraska remains under the influence of a
500hpa ridge while a sfc high builds in from the northern Plains.
Despite a strong signal of mid level frontogenesis over eastern
Nebraska, moisture is still hard to come by. GFS forecast soundings
show PWATs as low as 0.4 inch and 700hpa RH at 30% at KLBF and KVTN.
Temperature wise, backed off a degree or so for highs due to CAA and
the lack of the warming downslope flow at 850hpa. Max temps are
still on the warmer end of guidance (ECM) for full sunshine.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 323 PM CDT Tue Sep 27 2016

Wednesday night through Friday night...near stationary upper low
over the Great Lakes area will begin to move south as a significant
PV anomaly rounds the bottom of the main trough. Associated height
falls and advection processes will redevelop the surface low across
the Carolinas which will keep the surface ridge in place across
eastern NE. At the same time, increasing southwest flow aloft will
develop surface low pressure and surface trough in the lee of the
northern Rockies along the northern High Plains from MT to eastern
CO. This means an increasing pressure gradient and hence increasing
southerly winds across the western half of NE by late Thursday. The
resulting southeasterly low level flow will keep max and min temps
through the period near normal values. Some cloud cover may also
insue as mid level warm advection and therefore isentropic lift will
increase as weaker PV anomalies move northeast atop the weakening
Plains ridge.

Saturday and beyond...expansive upper trough moves onshore into mid
week. There are some significant differences in how the models
evolve individual short waves through the trough which ultimately
degrades confidence in the latter portion of the forecast period.
While increasing precip chances are included in the forecast, the
moisture transport will be in question as upper flow becomes
primarly zonal and if a downslope wind develops, low level moisture
will be limted. So the details are yet to be determined in latter


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1220 PM CDT Tue Sep 27 2016

VFR conditions will continue across western Nebraska through early
Wednesday afternoon. Very dry air in place will keep skc as winds
remain generally under 12 kts.




SHORT TERM...Snively
LONG TERM...Stoppkotte
AVIATION...Snively is the U.S. government's official web portal to all federal, state and local government web resources and services.