Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/16/19

Area Forecast Discussion

National Weather Service Phoenix AZ

 546 PM MST Fri Feb 15 2019

.UPDATE...
Updated 00Z aviation discussion.

&&

.SYNOPSIS...
An unsettled weather pattern will persist through next week
bringing well below normal temperatures. The first weather system
will slowly move through the region Sunday and Monday bringing
decent chances of rain over the deserts and snow over the high
terrain. Drier conditions will briefly settle in for next Tuesday
and Wednesday, but overnight lows are forecast to dip down to
around the freezing mark for colder desert locations. There is
also potential for a second and even wetter low pressure system
late next week.

&&

.DISCUSSION...
A step outside reveals a pretty nice day evolving as drying
commences now through the rest of today as yesterday`s disturbance
continues to eject into the Heartland. However, a flood warning
remains in effect for Tonto Creek in Gila County as the stream
continues to drain rain runoff from nearby mountains. An active
weather pattern will continue into the foreseeable future
ushering in seasonably cold temperatures and periods of wetness.
Another broad trough will begin to drop into the Intermountain
West this weekend with a cold airmass sinking behind along with
several embedded shortwaves rotating through the Southwest
enhancing the trough and rain chances. For lower desert locations,
the outlook for seeing daytime temperatures reaching 60 degrees
beyond Saturday looks murky at best.

As the broad trough dips further south this weekend, the area will
see limited chances for rain Saturday, primarily over the higher
terrain north and east of Phoenix, as the system may squeeze out
any remaining moisture from Thursday`s event. Saturday may be the
warmest day many folks across the lower desert experience for
quite awhile as the colder airmass takes residency across much of
the West. An embedded shortwave looks likely to impact the area
late Sunday/Monday which will allow the general broad trough to
dig even further south. The orientation of the trough will advect
some Pacific moisture into the Southwest as a 100 knot upper level
jet develops along with divergence aloft over central Arizona,
allowing some showers to develop Monday. During this time,
atmospheric heights will drop a bit with H5 heights nearing 548 dm
across the northern edges of the Sonoran Desert translating to
much colder surface temperatures. As of now, the central Arizona
desert areas are looking at 30-40% chance of rain Monday but the
mountains north and east of Phoenix might see upwards of 6-8
inches of snow as snow levels drop to near 4000 feet with this
colder airmass. Daytime temperatures for even the warmest desert
locations will sink into the 50`s beginning Sunday and lasting
potentially through all of next week.

Though it is nearly a week away, we are currently watching another
Pacific trough moving down the West Coast Wednesday into Thursday.
The outlier GFS operational run has been keeping this trough
farther inland, but the bulk of the GEFS members and the European
indicate the trough will track far enough west to tap into some
Pacific moisture. With the cold air already in place, this storm
will have the potential to produce significant snows over the
high terrain and possibly decent rains over the lower deserts.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Ceilings are finally beginning to lift at the Phoenix terminals
late this afternoon with aircraft soundings suggesting SCT to BKN
cloud decks will generally persist around 6 kft tonight with lower
ceilings to 4-5 kft possible at KIWA due to better ascent. Winds
will generally remain westerly at 5-10 knots tonight with an
easterly switch not expected except maybe a brief period at KIWA
around 03Z. Winds will increase tomorrow morning to 10-15 knots as
another front passes through the region with gusts up to 20 knots
during afternoon. Shower activity with the frontal passage should
remain well to the north and east of the terminals, but scattered
3-4 kft ceilings will be possible tomorrow morning until drier
air moves in behind the front at low levels for the afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty westerly winds up to 30 knots will continue for the next few
hours behind a front at KIPL before gradually decreasing to 25
knots after 03Z. W-SW winds will generally be weaker at KBLH due
to a less pronounced downsloping component to the flow relative
to KIPL, but 20-25 knot gusts will be possible during the
overnight hours. Both sites will continue to see 20-25 knot wind
gusts through tomorrow afternoon aside from a brief lull around
sunrise. Low cloud decks early tomorrow morning with 4-6 kft
ceilings will be possible, but confidence was too low to include
them in the TAF at this time.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Sunday through Thursday:
The active weather pattern will continue into next week with
temperatures well below normal through the period. Precipitation
chances will favor high terrain areas in Arizona Sunday and Monday
with good chances of wetting rain or snow over Arizona. A brief
break in the activity is likely for Tuesday before another weather
system moves in later on Wednesday. RH values will remain elevated
for much of the period finally lowering into the twenties for
Tuesday and Wednesday before rising again on Thursday. Periods of
breezy west winds can be expected most days.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Deems/Kuhlman
AVIATION...Hopper
FIRE WEATHER...Kuhlman