Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 180259
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
859 PM MDT THU APR 17 2014

.UPDATE...
SATELLITE IMAGERY INDICATES A RELATIVELY FLAT UPPER RIDGE
BUILDING NORTH INTO SOUTHERN MONTANA THIS EVENING. SOME MID TO
HIGH LEVEL CLOUDS HAVE DEVELOPED ALONG THE PERIPHERY OF THE RIDGE
AND PRODUCED SOME RETURNS ON KBLX RADAR TO THE NORTH OF BILLINGS.
TREND HAS BEEN FOR THESE RETURNS TO PUSH NORTHWARD. LOWERED POPS
FOR THIS EVENING BASED ON THIS. MODELS ALL WANT TO SWING ENERGY
INTO THE WEST OVERNIGHT AND PRODUCE SOME SHOWERS. HAVE MAINTAINED
POPS FOR THE OVERNIGHT AND MORNING HOURS. LOWERED WINDS MOST
LOCATIONS AS GRADIENT WAS PRETTY WEAK AT THE MOMENT AND THIS
SUPPORTED BY LIGHT WINDS. GRADIENT WILL TIGHTEN UP TOWARD MORNING
AND ALLOW WINDS TO PICK UP. LOWS WILL BE QUITE A BIT WARMER
TONIGHT WITH A WARMER DAY TODAY AND CLOUDS OVERHEAD. LOWS LOOK IN
GOOD SHAPE. TWH

&&

.SHORT TERM...VALID FOR FRI AND SAT...

CUMULUS FIELD HAD DEVELOPED OVER E PORTIONS OF THE AREA THIS
AFTERNOON PER VISIBLE SATELLITE IMAGERY IN RESPONSE TO A WEAK
SHORTWAVE CROSSING THIS AREA. TEMPERATURE/DEWPOINT SPREADS WERE
AROUND 20 DEGREES OVER MOST AREAS SO WILL NOT INCLUDE ANY EVENING
SHOWERS IN THE E.

A PACIFIC SHORTWAVE...SEEN OFF THE PACIFIC NW COAST THIS AFTERNOON
ON WATER VAPOR IMAGERY...WILL APPROACH THE AREA TONIGHT...PUSHING
A PACIFIC COLD FRONT TOWARD THE REGION. FRONTOGENESIS BAND WILL BE
JUST REACHING THE WESTERN ZONES BY 12Z FRI. SOME WARM ADVECTION
SHOWERS COULD REACH THE NW ZONES THIS EVENING...SO HAVE SOME POPS
IN THE NW THROUGH 06Z. SOME MOISTURE AND ENERGY WILL THEN ARRIVE
AHEAD OF THE FRONT OVERNIGHT SO HAD LOW POPS OVER THE W AFTER 06Z.
EXPECTING A WARM PREFRONTAL NIGHT AND MADE ONLY SLIGHT ADJUSTMENTS
TO THE MIN TEMPERATURES.

THE PACIFIC SHORTWAVE WILL MOVE THROUGH N MT FRI THROUGH FRI
NIGHT. MODELS PUSHED THE COLD FRONT THROUGH THE AREA IN TWO
PARTS...WITH THE SECOND PART LAGGING BEHIND THE FIRST ONE UNTIL
AROUND 00Z SAT. WITH THE FIRST PART OF THE FRONT MOVING THROUGH
THE AREA IN THE MORNING...HAVE EXTENDED THE SLIGHT CHANCE OF
SHOWERS FURTHER E THROUGH 18Z. KEPT THE HIGHER CHANCE POPS OVER
MOST OF THE AREA IN THE AFTERNOON AS MORE FRONTOGENESIS MOVES
THROUGH THE AREA. THE SLIGHT CHANCES IN THE SE LOOKED FINE. THE
WRF SHOWED A FEW HUNDRED JOULES/KG OF SURFACE CAPE NEAR THE SE MT
BORDER AND OVER SHERIDAN COUNTY BY 00Z SAT...SO KEPT THE MENTION
OF THUNDER OVER SE MT AND SHERIDAN COUNTY INTO FRI EVENING. THE
SECOND PART OF THE FRONT WILL SUPPORT CHANCES FOR SHOWERS FROM
KBIL E FRI EVENING. SHOWERS WILL QUICKLY EXIT THE AREA AFTER 06Z.
RAISED TEMPERATURES SLIGHTLY ON FRI BASED ON MIXING TO AROUND 700
MB AND MADE SLIGHT ADJUSTMENTS TO FRI NIGHT MIN TEMPERATURES.

A SHORTWAVE RIDGE WILL MOVE ACROSS THE AREA ON SAT BRINGING A WARM
AND DRY DAY. ANOTHER SHORTWAVE WILL PUSH A DRY COLD FRONT INTO THE
AREA SAT NIGHT. THE TEMPERATURES LOOKED REASONABLE FOR BOTH
PERIODS. ARTHUR

.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...

POTENTIAL STILL EXISTS FOR SIGNIFICANT PRECIP IN OUR AREA DURING
THE MIDDLE OF NEXT WEEK...BUT MUST STRESS GREAT UNCERTAINTY AT
THIS TIME.

ON SUNDAY...WEAK SHORTWAVE WILL HAVE LITTLE MOISTURE TO WORK WITH
AND WILL COME THRU EARLY IN THE DAY...SO WE MAY GET BY WITH ONLY
SOME MID AND HIGH CLOUD. WILL KEEP FORECAST DRY. MIXING WILL BE
FAIRLY STRONG SO WILL SEE ABOVE NORMAL TEMPS DESPITE THE POST
FRONTAL AIRMASS. THAT BEING SAID...BELOW ZERO 700MB TEMPS SUGGEST
HIGHS MOSTLY IN THE 60S...SO HAVE DROPPED FCST TEMPS JUST A BIT.

PACIFIC TROF WILL DEEPEN OFF THE COAST EARLY NEXT WEEK...ALLOWING
FOR AMPLIFIED SW FLOW OVER US MON/TUE...WITH HEIGHT FALLS OPENING
THE DOOR TO SHORTWAVE ENERGY LATE MON AND ESPECIALLY TUE. THERMAL
LOW IN SE MT ALONG WITH SOME HIGH PLAINS MOISTURE ADVECTION MAY
YIELD SOME EARLY SEASON TSTM ACTIVITY IN OUR CWA BY TUE.
OTHERWISE...TUE WILL BE THE DAY THAT SHOWER ACTIVITY REALLY
INCREASES DUE TO TROF PUSHING ASHORE AND STRONGER ENERGY LIFTING
OUT OF THE GREAT BASIN. THIS IS ALSO WHEN MODELS BEGIN TO DIFFER.

GFS/ECMWF PAINT COMPLETELY DIFFERENT SCENARIOS BY WED/THU. THE
GFS WRAPS A MOIST TROWAL INTO OUR REGION WED THRU THU...WITH
UPPER LOW SHIFTING JUST TO OUR EAST. THE ECMWF HAS MOVED TOWARD A
MORE PROGRESSIVE EVENT FOR US...LIFTING THE LOW NORTH AND ALLOWING
FOR DRIER AIR WITH INCREASED DOWNSLOPING. THE CANADIAN KEEPS THE
NORTHERLY JET FURTHER WEST BY 144 HOURS. ENSEMBLES AGREE IN THE
OVERALL LONGWAVE SHIFT...BUT ARE VERY SCATTERED IN THE IMPORTANT
DETAILS...SO IMPOSSIBLE NOW TO SAY WHICH WAY IT WILL GO FOR US.
AFTER A GOOD CHANCE OF SHOWERS TUE NIGHT PER AFOREMENTIONED GREAT
BASIN SHORTWAVE...WILL KEEP POPS BROADBRUSHED AT A LITTLE ABOVE
CLIMO IN THE WED/THU PERIOD. AGAIN...STRESS TREMENDOUS UNCERTAINTY
HERE. WILL CONTINUE TO ADVERTISE A POTENTIAL PCPN EVENT IN A
GRAPHIC/HWO.

IT SHOULD ALSO BE NOTED...IF THE GFS WERE TO VERIFY...850MB TEMPS
FALLING BELOW ZERO UNDER THE TROWAL COULD BE COOL ENOUGH FOR SOME
WET SNOWFALL AT LOWER ELEVATIONS...AND HEAVY SNOW FOR THE MTNS. SO
IF A GOOD PCPN EVENT DEVELOPS...AT THE VERY LEAST EXPECT RAIN TO
CHANGE TO ACCUMULATING SNOWFALL IN THE HIGH TERRAIN. SOMETHING TO
THINK ABOUT.

AS FOR TEMPERATURES...AFTER A MILD TUE EXPECT A DROP IN TEMPS OF
SOME MAGNITUDE FOR WED/THU. WILL KEEP DAY 6/7 TEMPS AS A
COMPROMISE BETWEEN THE WARMER ECMWF AND COOLER GFS. JKL

&&

.AVIATION...

VFR WILL PREVAIL TONIGHT WITH SCATTERED TO BROKEN MID AND HIGH
CLOUD OVER THE REGION. A COLD FRONT ON FRIDAY WILL BRING SCATTERED
SHOWERS AND LOCAL MVFR CONDITIONS AT LOWER ELEVATIONS...ALONG
WITH OCCASIONAL MOUNTAIN OBSCURATIONS. WEST WINDS WILL GUSTS TO 30
KTS OR HIGHER AT KLVM BY FRIDAY AFTERNOON. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 042/067 036/067 041/070 039/069 044/070 045/054 038/050
    04/W    30/U    00/U    00/B    22/T    55/W    44/W
LVM 042/064 033/066 039/068 037/069 041/067 039/052 033/052
    33/W    20/U    00/U    01/B    24/T    66/W    43/W
HDN 036/070 036/068 040/072 036/070 039/073 041/056 034/051
    04/W    30/U    00/U    00/U    12/T    45/W    44/W
MLS 037/068 036/065 040/072 039/069 041/071 043/058 036/051
    03/W    30/N    00/U    00/U    12/W    35/T    44/W
4BQ 037/072 036/068 041/073 039/070 042/074 044/062 033/052
    02/T    30/U    00/U    00/U    12/T    24/T    44/W
BHK 032/067 035/063 036/071 038/066 040/068 043/061 034/047
    02/W    30/N    00/U    00/U    12/W    34/T    44/W
SHR 037/072 034/066 037/070 036/069 039/074 042/058 037/050
    02/T    20/U    00/U    00/U    12/T    34/W    44/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS



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