Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 152311 AAA

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
511 PM CST Wed Feb 15 2017

.SHORT TERM...(This evening through Thursday)
Issued at 231 PM CST Wed Feb 15 2017

Lee cyclogenesis over northeastern Colorado will allow for a
return of southerly lower tropospheric flow late Thursday
afternoon. But before this occurs, winds will be westerly and even
slowly back to southwest through much of the day. The downsloping
west to southwest flow will continue to advect warm and dry air
across much of the region. As such, H85 temperatures will climb
some 3-4C from today, reaching the mid teens Celsius by mid-
afternoon. A modest warm up is forecast with most locations
reaching the upper 60s to lower 70s Thursday afternoon. The
exception is where snow pack remains, but even still, highs in the
lower to mid 60s are forecast. A surge of dry air off the rockies
will promote TD/s to lower into the teens and 20s. Td/T spreads
of potentially 40-50 F are possible, which would favor low
relative humidity. In addition, the dry air mass when combined
with mostly clear skies will create conditions favorable for a
good radiational event. Lows in the 20s and 30s tonight are
suggested by the latest guidance, but those readings may need to
be adjusted lower.

.LONG TERM...(Thursday night through Wednesday)
Issued at 231 PM CST Wed Feb 15 2017

The weather highlights for western and north central NEB in the
long term period are above normal temperatures (more often than
not 15-25 degrees above normal) and predominantly dry conditions.
There are some chances for showers Sunday afternoon-Monday, though
uncertainty remains with respect to coverage and timing. Highs
are expected to stay within the mid 50s to mid 60s range in this
time period.

Large scale pattern continues to be amplified aloft with an upper
ridge over the Central US that will dominate the sensible weather
across the region through Saturday. Said ridge will aid in keeping
conditions dry and temperatures above seasonal normal values. 500
hPa ridge will be initially over the Central Plains into southern
Manitoba with an area of low pressure beneath the base near the
Southern High Plains. Over the next 24 hrs, the ridge shifts to
the Upper Mississippi Valley and dampens some as a disturbance
lifts from the northern Intermountain West to the Northern Plains.
However, the positive PV anomaly is not going to impact the local
forecast area Friday outside a modest increase in sky cover and a
shift from westerly to northerly winds. The winds are expected to
shift in the afternoon wherein a surface trough extending from
the Canadian Prairies south through the Central High Plains late
Thursday Night will shift eastward to the Upper Mississippi Valley
to eastern NEB by late Friday afternoon. Even with relatively
cooler air advancing southward, highs are expected to read into
the mid and upper 50s in northwestern NEB to the mid and upper
60s across central NEB. Thereafter, ridging builds back aloft
across the Central Plains Saturday. Low-level southerly flow
becomes established early Saturday with warm air drawn back into
the local forecast area with highs expected to exceed normal
values again by 15 to 20 degrees.

The main interest beyond Saturday lies in the Sunday Night to
Monday time frame where there will be chances for showers,
possibly even an isolated thunderstorm. Of which, confidence in
the occurrence of an isolated thunderstorm is low such that there
is no mention at this time in the forecast  this will continue
to be monitored/adjusted as we get closer.

Next upper trough will be onshore the West Coast early Saturday
Night with a closed low near Baja California. The upper trough is
expected to move to Sonora Mexico-Central Great Basin-Northern
Rockies by Sunday afternoon then into Northern Plains Monday.
However, there continues to be differences in phase and amplitude
with this wave between the deterministic guidance. As such,
confidence remains below average with this system. Ahead of the
upper trough, moisture will be transported northward from the
Gulf at low-levels into the region late Sunday into Monday, and to
a greater degree across north central NEB. A surface low pressure
system is expected to develop and be positioned in the
Upper/Middle Missouri Valley by Sunday afternoon then track into
the Red River Valley/southern Manitoba by Monday afternoon. A
surface cold front is expected to advance eastward sometime
Sunday Night-Monday, however, the envelop of solutions appears to
still be considerable. While marginally unstable conditions
appear in the far south and southeast of the local forecast area
late Sunday Night into Monday, current thinking remains that the
overall likelihood is low. Beyond Monday, quieter and dry
conditions return through Wednesday.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 510 PM CST Wed Feb 15 2017

VFR is expected all areas.

Upper level ridging will continue to present mostly clear skies
overnight through Thursday afternoon.


Issued at 231 PM CST Wed Feb 15 2017

Fire weather headlines are not needed despite the projected
critically low relative humidity.  Winds will be largely influenced
by a deepening area of low pressure over northeastern Colorado.  The
pressure gradient would suggest wind speeds of 15 mph or less. Fuels
are ready to go along and south of interstate 80, but the further
north one heads, residual snow drifts and wet sfc conditions
increase.  Temperatures cool some on Friday with a greater influence
of southern plains moisture, relative humidity values are forecast
to increase.  Overall the pattern looks dry for the next 5 days, but
isolated shower chances increase late in the weekend and early
next week.




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