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Area forecast discussion...corrected 
National Weather Service Billings Montana
833 PM MDT Monday Apr 20 2015

Update...
no changes needed to the going forecast. Radar showed weak echoes
over NE Montana...ahead of the back door cold front that was over S
central Saskatchewan into northwest ND...this evening. The echoes
appeared to be middle cloud cover based on surface observations that
had temperature/dewpoint spreads on the order of 30 degrees.
Satellite showed the clouds over NE Montana as well as other middle level
clouds over the forecast area. Webcams showed a couple of showers
earlier in the evening...but these have dissipated with loss of
solar insolation. The back door front was forecast to move through
NE Montana overnight. New WRF and last couple of hrrr runs were dry
overnight. The dry forecast was in good shape based on the above.

Weak energy spilling over the upper ridge anchored over the
Pacific northwest into west Canada...will support partly cloudy skies
across the area overnight. Lift ahead of the back door front will
support middle clouds over the area ahead as well. Sky grids
reflected this well.

850 mb temperatures will remain fairly steady around +8 degrees c
overnight and forecast area will be in a prefrontal environment.
Based on the above...and recent trends of lows verifying at or
below guidance...the forecast mins looked reasonable. Relative humidity and winds
were also on track.

Dry low-levels will limit showers with the front on Tuesday. Going
forecast had probability of precipitation restricted to the higher elevations which seemed
reasonable. Arthur

&&

Short term...valid for Tuesday and Wednesday...

The short term is dominated by the ridge over the intermountain
west slowly shifting to the east. This will keep the area mainly
in cyclonic northwest flow. Several weak bands of energy will
move through the area...mainly over the mountains. Have continued
the slight chances of precipitation over the mountains through the
period. Tomorrow will see warmer temperatures approaching 70
degrees. Winds will begin to shift more easterly tomorrow
afternoon which will help to bring more moisture into the area.
Winds will be out of the east through much of the day on
Wednesday...so expecting rain chances to begin to increase...with
chances over the mountains and foothills...and a slight chance out
onto the plains. Reimer

Long term...valid for Thursday...Fri...Sat...sun...Mon...

The forecast area will still be in a blocking pattern through the
forecast period. This blocking pattern involves a deep upper low
over the Great Lakes area and a deepening trough off the Pacific
northwest. Montana and northern Wyoming will be in between these
systems and subject to a weak ridging pattern on Thursday. This
weak ridging breaks down on Friday as the eastern trough shifts
east a bit. This break down will allow weak energy to kick out of
the western trough and slide across the forecast area Friday
through next weekend. Easterly low level flow will keep some low
level moisture available and will thus keep probability of precipitation going. The best
chance of showers should be Saturday as a deep trough and surface
low moves across the area. Low level easterly winds will keep
temperatures to slightly above seasonal values. Twh

&&

Aviation...

VFR conditions will be over the area tonight through Tuesday evening.
Localized mountain obscurations will occur through Tuesday evening.
Arthur
&&

Preliminary point temp/pops...

Tuesday Wednesday Thursday Friday Sat sun Monday
-----------------------------------------------------------
bil 038/066 040/072 042/070 041/065 043/063 040/067 042/068
01/b 10/b 12/west 22/west 33/west 32/west 21/b
lvm 034/069 037/074 038/070 038/063 038/062 035/064 037/066
01/b 21/b 33/west 34/west 43/west 32/west 22/west
hdn 034/067 036/073 038/072 037/066 038/066 036/070 036/071
01/b 10/b 12/west 22/west 33/west 32/west 21/b
mls 032/063 034/069 036/068 038/066 039/066 038/068 038/069
00/u 10/b 01/b 22/west 33/west 32/west 21/b
4bq 031/064 033/069 036/068 038/064 039/064 037/068 036/070
00/b 10/b 01/b 23/west 33/west 42/west 21/b
bhk 028/057 029/063 031/063 034/062 035/061 034/066 033/064
00/u 10/b 00/north 23/west 33/west 42/west 21/b
shr 028/064 035/069 037/069 037/062 038/063 036/065 036/068
01/b 10/b 13/west 33/west 34/west 32/west 21/b

&&

Byz watches/warnings/advisories...
Montana...none.
Wyoming...none.

&&

$$
Weather.Gov/Billings

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