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Latest ZFP from WFO RIW
	
National Weather Service Local Forecast for Star Valley Ranch
Updated: 4 Jun 21:06 pm MDT

Tonight... Partly cloudy, with a low around 42. South southwest
wind 5 to 9 mph becoming southeast after midnight. 

Friday... Mostly sunny, with a high near 84. Southeast wind 6
to 9 mph becoming south southwest in the afternoon. 

Friday Night... A 30 percent chance of showers, mainly after
midnight.  Mostly cloudy, with a low around 56. Southeast wind 6 to 8
mph. 

Saturday... Showers likely, then showers and possibly a
thunderstorm after noon. Some of the storms could produce heavy rain. 
High near 68. South southwest wind 5 to 10 mph.  Chance of
precipitation is 90%.

Saturday Night... Showers and possibly a thunderstorm. Some of
the storms could produce heavy rain.  Low around 43. South southwest
wind 5 to 10 mph.  Chance of precipitation is 100%.

Sunday... Showers, with thunderstorms also possible after noon.
Some of the storms could produce heavy rain.  High near 51. South wind
5 to 8 mph becoming west southwest in the afternoon.  Chance of
precipitation is 90%.

Sunday Night... Rain showers before 2am, then rain and snow
showers likely between 2am and 4am, then snow showers likely after
4am. Some thunder is also possible.  Low around 34. Southwest wind 5
to 8 mph.  Chance of precipitation is 80%.

Monday... Snow showers before 9am, then rain and snow showers
between 9am and 10am, then rain showers after 10am. Some thunder is
also possible.  High near 44. Chance of precipitation is 90%.

Monday Night... A chance of rain showers before 9pm, then a
chance of rain and snow showers between 9pm and 1am, then a slight
chance of snow showers after 1am. Some thunder is also possible. 
Mostly cloudy, with a low around 32. Chance of precipitation is 50%.

Tuesday... A chance of snow showers before 9am, then a chance
of rain showers.  Partly sunny, with a high near 52. Chance of
precipitation is 30%.

Tuesday Night... A slight chance of showers and thunderstorms. 
Partly cloudy, with a low around 36.

Wednesday... Mostly sunny, with a high near 61.

Wednesday Night... Partly cloudy, with a low around 40.

Thursday... Sunny, with a high near 70.

	

Latest AFD from WFO RIW
	National Weather Service Riverton WY
518 PM MDT Thu Jun 4 2020

.SHORT TERM...This evening through Friday night
Issued at 251 PM MDT Thu Jun 4 2020

Early start to the shower activity in the far west this morning. A
weak vort within the westerly aloft seems to be responsible.
Convection appears to be weak at the time of this writing. Lifted
indices are positive in the west at the moment. Satl loop is
indicating trapped waves across the west at the moment indicative of
relatively stable air along with windy conditions in some areas(RKS
currently gusting to 56 mph coupled with 14 percent RH). Once the
clouds associated with these showers clear out, allowing for more
heating, we will see a fresh round of some convection today from the
next vort lobe later this afternoon and evening. Lifted indices are
progged to be around -3 in  the far west, -1 over most areas, and -4
over Johnson County. With 30 knot westerly winds at 700mb today,
most convective cells will likely occur with gusty winds.
Thunderstorms will likely be most numerous in our northern zones
today closer to the jet energy. As thunderstorms develop in northern
Wyoming today due to the jet energy there, and they move east into
juicier air from where dew points are in the upper 30s to low 40s,
into where dew points are in the upper 40s, and where lifted indices
are already near -4, storms will strengthen in areas like northern
Johnson County today. In fact, SPC now has northeast Johnson County
in a slight risk area for severe weather for today.

The central and southern portions of the CWA east of the Divide as
well as Sweetwater County will have a minimum RH that will bottom
out to the low to mid teens this afternoon where brisk winds are
occurring. An RFD is addressing this.

Friday will be a quieter day as a flat ridge builds into the area
along with a resultant subsidence inversion. These warmer
temperatures aloft will suppress instability. The subsidence
inversion will begin to lose its identity later Friday afternoon, so
a few isolated thunderstorms could occur late in the day, especially
in the northwest where higher capes will be. Many areas on Friday
could see the hottest temperatures so far this season with highs in
the low to mid 90s in the Wind River and Big Horn Basins and 80s
elsewhere. The minimum RH will be in the low teens in the same areas
that the RFD is currently addressing now. The winds will be brisk,
but not as strong as today. An RFD will likely again be needed in
the same areas for Friday.

A closed low well off the Baja Ca coast will make landfall onto the
southern California Coast Friday and then become an open trough
Friday night. This trough will rapidly track northeast to Wyoming
Friday night. The GFS appears to be the fastest with this feature
and the Euro the slowest. Clouds and showers will increase sometime
during the night from the southwest from this feature Friday night.
This trough will deliver some active weather over the weekend which
my esteemed colleague will address in the long term.

.LONG TERM...Saturday through Thursday
Issued at 251 PM MDT Thu Jun 4 2020

The open trough over the southwest US will get ejected over Wyoming
during the day Saturday. This system will bring widespread rain
showers and thunderstorms through the day. Activity will start west
of the Divide, then spreading across the east in the afternoon.
Precipitable water values are in the 0.6 to 1 inch range so
precipitation will have the potential to be heavy at times. Models
are still a bit conflicted on the strength of storms. GFS has only a
few small areas of CAPE above 200 J/kg available, while NAM is
bringing in a large swath of 600 to 1000 J/kg across the western
mountains. I have split the difference, including heavy rain and
small hail into the grids for now.

On Sunday morning, models show a stout trough over the western U.S.
with the upper low centered over Oregon. The upper low is expected
to shift into central Idaho by 00Z Monday. Frontogenesis is expected
Sunday over the forecast area as the a strong west to east
baroclinic zone will develop across western/central Wyoming Sunday.
This strong Pacific cold front is then expected to surge east across
the forecast area Sunday night. The main mid-upper trough axis looks
to pull across the area on Monday/Monday night. There is a very good
chance of significant precipitation over the west as a strong jet
streak pulls across the area with decent QG forcing. Snow levels
over the far west could be down to around 8000 feet Sunday. Snow
levels will drop to valley floors west of the Divide Sunday night,
but the most of the precipitation should have shifted away, but
would not be surprised to see some snow in the western valleys and
basins Sunday night. Precipitation totals ar in the 0.50 to 1.00
inch range Saturday into Sunday night west of the Divide. Could see
a few inches of snow in the mountains while any higher amounts in
the lower elevation might run risk of some flooding. Will continue
to monitor.

The bulk of chances of precipitaion with this system will continue
until the trough axis pulls across the area Monday/Monday night. The
precipitation Monday is expected to be much lighter than what occurs
Sunday. A trailing shortwave could give a slight chance of shower
activity especially over the northwest and north on Tuesday.

Ridging develops Wednesday and Thursday with mainly dry conditions
and a warming trend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 518 PM MDT Thu Jun 4 2020

TAF sites should remain VFR through the entire period. Isolated
showers and thunderstorms are still possible across the north, but
should not impact TAF sites. Westerly winds have increased at
most TAF sites this afternoon, but should decrease around sunset
and return to typical nocturnal drainage flows. Conditions are
expected to be similar to today on Friday, but winds will not be
as strong.

&&

.FIRE WEATHER...
Issued AT 251 PM MDT Thu Jun 4 2020

A weak weather system will move across the state and bring isolated
to widely scattered showers and thunderstorms, most numerous in
northern Wyoming for the rest of this afternoon. A gusty wind will
develop in the afternoon with some elevated fire behavior expected
in portions of central and southern Wyoming with relative humidity
falling to around 13 percent. Mixing and smoke dispersal will range
from good in portions of the north to excellent in the west and
south. Even hotter temperatures and slightly lower RH are expected
for Friday, but winds will be a little lighter. Still, elevated fire
conditions are also expected again Friday. Saturday will feature
unsettled weather with considerable cloudiness, along with showers
and thunderstorms, and increased wind. Much cooler and wet
conditions along with some mountain snow is expected by early next
week.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
	

Latest GFS MOS for JAC
	KJAC   GFS MOS GUIDANCE    6/04/2020  1800 UTC
DT /JUNE  5                  /JUNE  6                /JUNE  7
HR   00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 12 18
N/X              39          80          53          64       42
TMP  65 55 47 43 41 55 70 78 76 68 62 58 55 60 62 61 59 52 46 43 49
DPT  40 44 44 43 41 46 47 42 42 45 46 46 46 47 46 46 46 47 45 41 33
CLD  SC CL CL BK BK SC BK BK SC OV OV BK BK BK OV OV OV OV OV OV OV
WDR  22 21 06 36 36 35 19 20 20 36 35 01 01 20 20 18 17 21 20 19 20
WSP  19 08 03 03 05 02 10 17 14 19 07 12 13 07 10 07 13 13 10 08 13
P06         3     5     0     0    12    11    25    56    64 49 36
P12               7           1          15          63       72
Q06         0     0     0     0     0     0     0     2     2  1  1
Q12               0           0           0           2        3
T06     16/ 3  6/ 0  9/ 4 17/ 9 16/ 5  7/ 0 23/ 4 49/ 0 23/ 6 14/ 0
T12                  9/ 4       27/ 9       25/ 4       57/ 8 16/ 3
CIG   8  8  8  8  8  8  8  8  8  8  8  8  8  8  7  7  7  5  5  5  6
VIS   7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7
OBV   N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N



614
FOUS25 KWNO 041800

-----------------

KJAC   GFSX MOS GUIDANCE   6/04/2020  1200 UTC
FHR  24  36| 48  60| 72  84| 96 108|120 132|144 156|168 180|192
     FRI 05| SAT 06| SUN 07| MON 08| TUE 09| WED 10| THU 11|FRI CLIMO
N/X  41  81| 52  64| 45  50| 35  48| 32  56| 35  65| 39  66| 41 37 70
TMP  43  79| 54  59| 46  44| 36  46| 34  54| 36  62| 40  63| 42
DPT  41  41| 46  47| 43  37| 34  30| 28  31| 34  33| 37  36| 38
CLD  PC  PC| PC  OV| OV  OV| OV  OV| PC  PC| PC  PC| PC  PC| PC
WND  19  16| 16  15| 16  15| 16  21| 17  20| 17  24| 21   9| 14
P12   3   0| 14  78| 74  67| 48  57| 34  18| 28  20| 16  15| 19999999
P24       4|     85|     79|     76|     38|     32|     21|      999
Q12   0   0|  0   3|  2   2|  1   2|  1   0|  0   0|       |
Q24       0|      3|      3|      2|      1|      0|       |
T12  12  23| 18  69| 29  35| 14  30| 11  10|  7  19| 12  18| 19
T24        | 23    | 80    | 42    | 33    | 10    | 25    | 26

	
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