Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 172145
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
345 PM CST Fri Feb 17 2017

.SYNOPSIS...
Issued at 345 PM CST Fri Feb 17 2017

H5 analysis from earlier this morning had a continuation
of split flow across the CONUS. Attached to the southern stream, a
closed low was located over central Texas. Downstream of this
feature, a low amplitude ridge extended north into the mid
Mississippi valley. Further north and west attached to the northern
stream, a trough of low pressure was located off the coast of
California with a broad area of southwesterly flow extending into
south central Canada. Within this flow, a nice shortwave was noted
over Saskatchewan and eastern Montana. East of the south central
Canada ridging, a closed low was located over the Canadian Maritimes
with a trough extending south into the western Atlantic. At the
surface, a cold front pushed through the forecast area today and was
more of a wind shift line as cold air advection was weak with its
passage. In fact, the strongest cold air advection was trailing the
front by 200 to 300 miles as 50s were noted over the northern
Nebraska panhandle. Elsewhere across western and north central
Nebraska, temperatures were in the lower 60s in the north and upper
60s in the south.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 345 PM CST Fri Feb 17 2017

Another very mild day across the area, even behind a weak Pacific
cold front. Surface high pressure will slide across the central
plains tonight. Have again opted for the lower end of guidance for
low temperatures due to the dry air and light winds. Should see
favored colder spots drop into the mid 20s.

As the surface high moves east of the area Saturday, south winds
will begin to increase. Gusts by afternoon could approach 25 mph
across northwest Nebraska. Otherwise some increase in high clouds
will occur ahead of a fierce Pacific storm system currently moving
onshore California. Highs most if not all areas should reach the 60s
once again. Perhaps just a bit cooler across far northwest Nebraska,
where a bit of snow cover remains.

.LONG TERM...(Saturday night through Friday)
Issued at 345 PM CST Fri Feb 17 2017

Mid range: Saturday night through Monday: In the mid range, fog
potential Saturday night into Sunday morning, followed by the threat
for showers and thunderstorms Sunday night into Monday morning are
the main forecast concerns. Beginning Saturday night, ridging aloft
will begin to break down and move east, being replaced by an
approaching trough of low pressure aloft from the west. At the
surface, a trough of low pressure will deepen along the front ranges
of Colorado and Wyoming, increasing southerly winds across western
and north central Nebraska overnight Saturday night. Moisture
advection will increase as well overnight across the eastern half of
the forecast area. SREF probabilities, as well as the NAM12 visby
product indicate a good potential for advection fog overnight
Saturday night into early Sunday morning and will include it in the
latest forecast. By Sunday afternoon, a strong shortwave trough of
low pressure will begin to lift across the four corners into
southeastern Colorado. Looking at the latest NAM12 solution
elevated, as well as surfaced based instability increases Sunday
evening from southwestern Nebraska into central and northern
Nebraska overnight. With SB Lifted Indexes of -2 to -4C and SB CAPES
of 500 to 1000 J/KG, felt it was time to initiate a mention of
thunderstorms Sunday evening into the overnight. This is in
agreement with the latest SWODY3 which has us outlooked in the
general thunderstorm category. Deep layer shear is pretty strong
with this system, and feel the meager instability is not strong
enough to overcome the strong vertical wind shear. That being said,
the threat for severe storms appears low at this time. On Monday,
the upper level trough of low pressure will cross Nebraska into
eastern South Dakota. The threat for showers will continue into
midday Monday.

Monday night through Friday: The before mentioned trough of low
pressure will track east of the forecast area Monday night. Through
Wednesday, zonal flow, followed by west southwest flow aloft will
dominate across the central CONUS. Mild temperatures will continue
through Wednesday with highs in the 60s and possibly lower 70s for
Tuesday. With flow aloft being west southwesterly and the pacific
moisture tap wide open we could see an abundance of high cloudiness
early next week which may foul up the temperature forecast. That
being said, the current forecasted highs Monday, Tuesday and
Wednesday may be "optimistic". Beginning late Wednesday, a trough of
low pressure will track across the central and northern Rockies,
emerging onto the plains late next week. The mid range model
solutions have trended north with the upper low`s track with this
mornings runs, and it appears at this time, locations across South
Dakota and northern Nebraska may be under the gun for accumulating
snows late next week. The upper level low track is anticipated to
fluctuate some with the next several model forecast runs, so the
precipitation forecast will change over the next several days. One
forecast aspect which we do have some degree of confidence in is the
wind with this system. The superblend winds for Thursday/Friday were
too low and were blended with the CONSMOS which brought the winds up
into the windy category.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 220 PM CST Fri Feb 17 2017

VFR will continue across the entire region through Saturday. Winds
will gradually shift to the south Saturday morning. The only
clouds should be scattered high cirrus clouds.


&&

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

$$

SYNOPSIS...Buttler
SHORT TERM...Taylor
LONG TERM...Buttler
AVIATION...Taylor



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