Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 250449
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1149 PM CDT Wed May 24 2017

.SYNOPSIS...
Issued at 339 PM CDT Wed May 24 2017

H5 analysis from earlier this morning had a closed low
over northern Missouri with a trough extending south into the
northern Gulf of Mexico. With this feature, 50-100 meter falls were
noted from the Ozarks southeast into the lower Mississippi Valley.
Upstream of this low, a low amplitude ridge extended from Wyoming
into western Ontario. Upstream of this feature, a closed low was
located over southeastern British Columbia. Ht. falls in association
with this low ranged from 150-250 meters across eastern Washington,
western Montana, and southern portions of British Columbia and
Alberta. At the surface: High pressure had moved south of the
forecast area into Kansas this afternoon. Further west, a lee side
trough of low pressure had developed from eastern Montana into
northern Colorado. Southerly winds had begun to increase across the
panhandle and western portions of the forecast area this afternoon,
while winds were light in the eastern portion of the forecast area.
Temperatures as of 3 PM CDT ranged from 62 at O`Neill to 72 at
Gordon and Ogallala.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 339 PM CDT Wed May 24 2017

Tonight and Thursday...Over the next 24 hours, limited
precipitation chances will be the main forecasting concern. For
tonight: The H5 low will track across far southern Canada from
southern Alberta into southern Saskatchewan. This feature will force
a cold front into the northwestern cwa by 12z Thursday. Upper level
forcing will be largely absent with the frontal passage with the best
mid and upper level lift focused well north of the forecast area.
Low level moisture remains limited as well so will hold onto a dry
forecast tonight, though we may see some increased cloudiness in
association with the front toward 12z. On Thursday, the front will
track across the forecast area during the morning and early
afternoon hours. As it does it will encounter some mid to upper 40s
dew points in the north central and northeastern portion of the
forecast area. Though mid level forcing remains weak at best, we
still could see a stray shower develop in the north and northeastern
forecast area during the midday to early afternoon hours. The
inherited forecast had this mentioned and just refined the timing
toward the latest model guidance. Disconnected from precipitation in
the northeast, a shortwave will approach the central Rockies
Thursday morning, crossing it and emerging onto the front range of
Colorado Thursday afternoon. This feature will initiate convection
along the front range of Colorado. An approaching jet streak will
lead to enhanced lift as thunderstorms cross eastern Colorado into
western Kansas and southwestern Nebraska. Attm, am expecting
convection to move along the frontal boundary which is expected to
be oriented from east central Colorado into north central Kansas.
Some of this may impact the southern third of the forecast area late
Thursday afternoon into Thursday night. ATTM the main severe threat
should remain south of the forecast area, as we will be well north
of the frontal boundary Thursday evening. Also the left front
quadrant of the jet will be focused over northern Kansas.

.LONG TERM...(Thursday night through Wednesday)
Issued at 339 PM CDT Wed May 24 2017

Mid range...Thursday night through Saturday...In the mid range,
precipitation chances in association with a lead short wave
Thursday night, then a stronger disturbance Friday night into
early Saturday is the main forecast challenge. Ongoing convection
Thursday evening, will continue to track across Kansas overnight.
This will force a frontal boundary and low pressure into northern
Oklahoma. Friday will be mainly dry, however, precipitation
chances will then increase Friday evening into the overnight as a
second, stronger disturbance lifts east of the Rockies. As has
been the case for the past couple of days, there is some
differences as to where the greatest threat for convection will
set up Friday night. The GFS is further north and impacts the srn
cwa with a MCV Friday night. The ECMWF and the 12z NAM 12 soln
this morning develop this feature over northwestern Kansas lifting
it over northern Kansas Friday night into Saturday morning. Have
continued to trend pops more toward the EC and NAM12 solns as all
three solutions have the warm front and surface low over northern
Oklahoma. Thinking here is that we are too far north of the front
to get the heaviest pcpn up to the I80 corridor. That being said,
limited pops to 40 to 50 percent Friday night along the Interstate
with some 50 to 60 pops in far southwestern Nebraska.

Saturday night through Wednesday...Drier conditions will set in
Saturday night through Sunday as the upper level low drifts slowly
east across southern Canada. The next chance for precipitation
across the forecast area will be late Monday in the northeast as a
disturbance rotates south of the closed low across the eastern
Dakotas into northeastern Nebraska. The closed low will finally lift
into eastern Canada late Tuesday into Wednesday. This will allow
ridging to build east of the western CONUS. We will remain in
northwesterly flow aloft through Wednesday, which would normally be
favorable for thunderstorms this time of year. However, boundary
layer moisture return appears limited at this time, so mainly dry
conditions are expected. Temperatures during the period will still
be below normal with highs in the upper 60s/lower 70s, which is
5 to 10 degrees below normal.

&&

.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...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...ET



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