Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 221720
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1220 PM CDT Mon May 22 2017

.SYNOPSIS...
Issued at 331 AM CDT Mon May 22 2017

Skies were clear to partly cloudy across north central Nebraska
while partly to mostly cloudy across southwest Nebraska. An upstream
disturbance was located from southwest North Dakota into southeast
Montana.

&&

.SHORT TERM...(Today and tonight)
Issued at 331 AM CDT Mon May 22 2017

Today/Tonight...An upstream disturbance currently extending
southwest North Dakota into southeast Montana will begin to move
into western Nebraska today. Mid level lapse rates reach 7.5 c/km
this afternoon. Instability will be weak as 800mb capes only reach
200-400 j/kg in some areas. The best upscale lift will be along and
ahead of the 500 mb trough axis, with best shower chances from 18z-
03z, then mainly exiting southwest zones after 06z. Morning shower
chances north central, with shower and thunderstorm mention
afternoon/evening all areas. While no strong storms are expected,
pea size hail and gusty winds to 45 mph with a few thunderstorms.
Skies should start our mostly sunny, followed by increasing clouds
northwest through southeast by afternoon. Highs from the low 60s
northwest to upper 60s southeast. Accompanying the upper trough
passage, a cold front will bring increasing northwest winds of 10-20
mph late morning thorugh afternoon. Winds decouple early evening to
5 to 10 mph overnight. Lows tonight from the upper 30s to lower 40s
with skies remaining partly to mostly cloudy.

.LONG TERM...(Tuesday through Sunday)
Issued at 331 AM CDT Mon May 22 2017

The models continue to advertise a shortwave possibiliy impacting
the forecast area in the form of rain showers on Tuesday. Most of
the energy will have already passed to the south and east. the
greatest chances are east of the forecast area associated with an
upper level low, but weak instability, moisture and forcing would
suggest at least a slight chance mention through 00z Wednesday.
Subsidence quickly fills behind the passing wave Wednesday evening
with light winds associated with a weak high pressure system.
With the dry forecast and expected clearing skies, temperatures
will fall rapidly overnight with guidance pegging lows in the mid
30s over much of the forecast area. Our northwestern zones are
most likely to see frost related headlines, but with temperatures
hovering in the mid to upper 30s elsewhere, frost headlines for
other zones cannot be discounted at this time.

Upper ridging building east across the northern and central plains
will keep temperatures seasonal through Thursday, but a strong
BC/PAC NW upper level trough will rapidly breakdown the ridge to
the east allowing for active southwest flow. Thus, rain and
thunder chances increase for late week and the coming weekend.
Overall model agreement in the long term is good with the large
scale pattern, but timing on the individual low amplitude
waves/disturbances have yet to be resolved. So will cap pop
chances Thursday and beyond at chance. Otherwise, with the active
sw to near zonal flow late week and weekend, temperatures will be
slightly below average.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1220 PM CDT Mon May 22 2017

Scattered showers and thunderstorms will affect western Nebraska
this afternoon and evening as a cold front approaches from the
north. Most of the cumulus should remain in the VFR cigs, but
gusty, erratic winds are likely with any shower. The ambient wind
will generally be northwest, gusting above 20 kts at times. Any
shower activity will likely diminish after sunset. Northwest winds
will lighten overnight and pick up again mid morning Tuesday.

&&

.HYDROLOGY...
Issued at 331 AM CDT Mon May 22 2017

Rivers of concern include: North Platte, South Platte, and Elkhorn.
A flood warning continues on the North Platte near Lewellen
affecting Garden and Keith counties due to reservoir releases
upstream and recent precipitation. The North Platte river is
expected to reach near flood stage today, then fall slightly and
remain high through the rest of the week. Elsewhere, the South
Platte river is expected to go up from northeast CO to Roscoe, NE to
North Platte, NE attributable to heavy precip and snow melt across
eastern CO. However, there is uncertainty in how much river levels
will rise beyond Julesburg, CO. At Roscoe, the river is forecast to
rise above Action Stage on Thursday, and above Action Stage Friday
at North Platte. Those with interests near or on the South Platte
river should stay tuned for updates. Lastly, the Elkhorn River near
Atkinson has risen slightly above action stage tonight.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SYNOPSIS...Roberg
SHORT TERM...Roberg
LONG TERM...Jacobs
AVIATION...Snively
HYDROLOGY...Roberg


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