Area Forecast Discussion
Issued by NWS North Platte, NE

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734
FXUS63 KLBF 250902
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
402 AM CDT Thu May 25 2017

.SYNOPSIS...
Issued at 327 AM CDT Thu May 25 2017

At 08z...a weak cold front extended from near Rapid City SD through
Douglas and Casper WY as surface low pressure extended along the
central high plains. A line of isolated showers and storms extended
near a warm front aloft north to south from the central Dakotas
through Central Nebraska. Otherwise skies were clear to partly
cloudy in western Nebraska. temperature much milder than 24 hours
ago currently ranging in the 50s.

&&

.SHORT TERM...(Today and tonight)
Issued at 327 AM CDT Thu May 25 2017

Today/Tonight...An upper level low in southern Saskatchewan will
pivot slowly east today as the upper trough extending south from the
low pushes east into the Northern and Central Plains. This will push
a weak cold front slowly through western nebraska today. Winds
behind the front will turn to the north, but remain light at 5 to 10
mph. The front will actually aid in warming up temperatures across
the forecast area. Southwest Nebraska should reach the mid to upper
70s, with near 73 across the east. In the northwest slightly cooler
today near 70. Isolated showers are possible today in vicinity of
the front. Models however are focusing on development to be near a
disturbance in north central CO and southeast WY at 18z today, which
will translate eastward into the southern half of the panhandle and
northeast CO. The leading edge of storm development should reach the
southeastern panhandle by 20z and eastward into southwest Nebraska
by 00z as pops increase to 30 to 50 percent. Parameters are
favorable for a few strong or severe storms late this afternoon and
evening across the southeast panhandle into southwest Nebraska.
Surface based capes increase to around 1500 j/kg near and south of
Oshkosh through North Platte along with 0-6km shear up to 40 kts.
Lower and mid level lapse rates are also fairly steep.

For tonight, a 40 to 60 percent chance for showers and storms this
evening southeast panhandle and southwest, with a few strong or
severe storms possible.  A slight chance for showers and storms near
and just north of highway 2.  Chances diminish after midnight.
Northeastern areas should remain dry overnight. Lows tonight range
from the mid 40s northwest to around 50 southeast.

.LONG TERM...(Friday through Wednesday)
Issued at 327 AM CDT Thu May 25 2017

Upper level low pressure will slowly wobble across southern
Canada through Tuesday before finally lifting northeast into
Quebec Wednesday. This will be the main weather player for the
central and northern plains through Tuesday before it looses it`s
grip by Wednesday.

The main precipitation chances will be early in the forecast
period (Friday and Saturday), as an upper level disturbance
tracks from the northern Rockies through the central plains on
the southern periphery of the large Canadian upper low.

There continues to be a concern for a few severe thunderstorms
across southwest Nebraska late Friday afternoon and evening.
Increasingly moist southeast low level upslope flow, will combine
with steep mid level lapse rates and surface heating and yield
surface based cape values approaching 1500 J/KG by late Friday
afternoon. As the upper level disturbance approaches, large scale
lift will aid in thunderstorm initiation in the favorable upslope
environment across the panhandle. These storms will track east-
southeast across much of the area through the evening and
overnight, likely forming upscale into an MCS. Prior to MCS
development, isolated supercells with the potential for large hail
will exist within area of higher instability across southwest
Nebraska.

The upper level disturbance will take it`s time crossing the area
Friday night into Saturday, with showers likely lasting into at
least early Saturday afternoon. Saturday will be the coolest day
of the holiday weekend, with highs in the 60s.

By Sunday into Monday, the upper low will be located to north of
the Great Lakes. This will keep our area in northwest flow aloft,
with a drying trend is seen in the boundary layer through the mid
and upper levels. This will allow for more sunshine and have
removed any mention of rain these days. Have warmed highs Sunday
as thermal ridging develops ahead of a weak southward moving cold
front that arrives Monday. Low to mid 70s expected Sunday with mid
60s to around 70 behind the cold front Memorial Day. Similar highs
in the upper 60s to mid 70s expected both Tuesday and
Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1145 PM CDT Wed May 24 2017

Latest satellite imagery and surface plot shows a few areas of
mid- and high-level clouds moving eastward across the NEB
Panhandle and western NEB. VFR conditions are present with high-
end VFR ceilings (greater than 7 kft). While earlier radar
imagery showed returns this evening across the Panhandle and
southwest SD, this activity has since diminished. Dry conditions
are expected rest of tonight. The main aviation concerns are LLWS
conditions overnight and then shower/t-storm chances tomorrow
afternoon/evening.

LLWS conditions are expected to affect terminals outside the
eastern NEB Panhandle overnight into early morning. Local VAD wind
profile from 1130 PM CDT shows the low-level jet present with
winds of 55 and 58 kts at 250 m (~820 ft) and 500 m (~1640 ft),
respectively. For the TAF, an upper height of about 1000 ft AGL is
expected with 50-60 kts southerly winds at the top of the wind
shear layer. Otherwise, an increase in mid- and high-level clouds
are expected tomorrow. Shower and thunderstorm chances increase
over southwest NEB (west of the North Platte terminal) mid
afternoon then chances spread eastward across to central NEB and
the southern Sandhills during the evening.

&&

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

$$

SYNOPSIS...Roberg
SHORT TERM...Roberg
LONG TERM...Taylor
AVIATION...ET



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