Area Forecast Discussion
Issued by NWS North Platte, NE

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880
FXUS63 KLBF 222329 AAA
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
629 PM CDT Mon May 22 2017

.SYNOPSIS...
Issued at 320 PM CDT Mon May 22 2017

H5 analysis this morning had a closed area of low
pressure over southwestern Ontario. West of this feature, an east to
west trough of low pressure extended west from this feature into
northern Montana. A strong shortwave was noted over Northern Montana
and had tracked south into sern Montana as of midday. A secondary
shortwave was located over central South Dakota as of noontime. In
advance of both of these features, showers were present across South
Dakota into northern Nebraska. Further south, isolated
thunderstorms had initiated along and south of Interstate 80 and
were tracking southeast. With the approach of the shortwaves,
abundant mid and high level cloudiness had developed across western
and north central Nebraska this afternoon. At the surface, a surface
trough of low pressure had tracked through most of the forecast area
as of midday, and was located from east central Nebraska, southwest
into south central Nebraska.  Winds were more northwesterly behind
the trough while along and east of this feature, winds were from the
west or southwest. Temperatures as of 3 AM CDT ranged from 52 at
Gordon to 71 at Imperial.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 320 PM CDT Mon May 22 2017

Tonight and Tuesday...Precipitation chances over the
next 24 hours is the main forecasting challenge in the short term.
For tonight: Upper level low pressure, currently over southwestern
Ontario, will drop south into Minnesota. The elongated trough and
shortwave, currently over Sern Montana/Nern Wyoming, will drop
southeast into western Nebraska through this evening. The threat for
scattered showers with embedded thunderstorms, will continue this
evening. Into the overnight, instability will weaken substantially
as the surface cools and lapse rates decrease. Skies will remain
partly to mostly cloudy overnight as the trough axis aloft remains
north of the area through Tuesday afternoon. On Tuesday, the
trailing shortwave trough will approach and track through the
forecast area. Very steep lapse rates will develop Tuesday
afternoon, increasing the threat for isolated showers during peak
heating. Decided against the mention of thunder however, as Lifted
indexes, both elevated and surface based are well above zero C
during peak heating.

.LONG TERM...(Tuesday night through Monday)
Issued at 320 PM CDT Mon May 22 2017

Mid range...Tuesday night through Thursday night...The H5 trough
axis will be through the forecast area by Tuesday evening with
clearing skies and surface high pressure building into the region.
The surface high will be located over south central into north
central Nebraska by 12z on Wednesday morning. Dry air, clear skies
and light winds will allow overnight lows to reach the lower to
middle 30s in the west to around 40 in the east. Did go ahead and
introduce some patchy frost wording in portions of the eastern
panhandle and northwestern sandhills Wednesday morning, for areas
where the temperature bottoms out at 35 degrees or less. Will hold
off on any headlines right now as the guidance temps for Tuesday
night continue to fluctuate with each model run. As for North
Platte and Valentine, frost is not expected attm. Dry conditions
will continue into Wednesday and Wednesday night as a low
amplitude ridge aloft builds into the central plains. This feature
is in advance of a secondary approaching area of low pressure
over southwestern Canada. By Thursday afternoon, the upper level
low will force a cold front into the western Dakotas. This feature
will approach the northwestern forecast area Thursday afternoon,
passing through the forecast area Thursday night. This will lead
to an increased threat for showers and thunderstorms late Thursday
into Thursday night. Attm, the bulk of moisture will be locked
into the southern plains, so the best chances for rain will be in
the west early on, with a shift to the southern cwa Thursday
night.

Friday through Monday...Looking at the mid range model solutions,
there are two trains of thought going on. Both have a closed low
tracking across southern Canada this weekend. However there are some
differences in the strength and timing of a trailing shortwave which
crosses the central Rockies this weekend. The GFS is more amplified
and wetter while the EC is much more subdued with the precipitation
threat. Given the way the EC has been verifying lately, blended the
forecast toward the drier EC solution. That being said, there will
be a continued threat for precipitation through Saturday with mainly
dry conditions expected for Sunday into Monday. On Saturday, the
bulk of precipitation will go south into Kansas as a frontal
boundary is expected to lie down along the KS/OK border.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 628 PM CDT Mon May 22 2017

VFR is generally expected this evening through 00z Tuesday
evening.

The model consensus suggests the scattered shower and isolated
thunderstorm activity will decrease this evening and dissipate
05z-06z.

Tuesday...a portion of the upper low across the Great Lakes/Upper
midwest drifts south into Iowa. Cold air aloft is expected to
produce isolated to perhaps scattered showers and thunderstorms
late Tuesday morning through early Tuesday evening. The models
suggest coverage would be higher across Ncntl Neb than Wrn Neb.

&&

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

$$

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC



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