848 
FXUS65 KCYS 051821
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1121 AM MST TUE FEB 5 2013

.UPDATE...

AVIATION...18Z TAFS...VFR CONDITIONS WILL CONTINUE THROUGH THE
PERIOD WITH A MID AND UPPER LEVEL DECK MOVING OVERHEAD FROM THE
WEST. SOUTHWEST WINDS WILL GENERALLY BE BREEZY TODAY ALONG AND
WEST OF THE LARAMIE RANGE...AND WILL BE LIGHT ACROSS THE EAST. A
FRONT MOVING THROUGH THE EASTERN PLAINS TOMORROW MORNING WILL
SHIFT WINDS TO THE WEST AND NORTHWEST WITH GUSTS OF 20 TO 30 KTS
LIKELY ACROSS THE ENTIRE AREA THROUGH THE AFTERNOON. 

&&

.PREV DISCUSSION... /ISSUED 1045 AM MST TUE FEB 5 2013/ 

UPDATE...
WATER VAPOR IMAGERY LOOP SHOWED THE MID/UPPER LEVEL RIDGE TO THE
WEST OF THE CONTINENTAL DIVIDE LATE THIS MORNING. MID/UPPER LEVEL
MOISTURE WAS ADVANCING EAST-SOUTHEAST OVER THE COWBOY STATE AHEAD
OF THE RIDGE AXIS. WINDS ALOFT WILL GRADUALLY BACK FROM NORTHWEST
TO WEST THIS AFTERNOON AS THE RIDGE NEARS. THE LOW LEVEL GRADIENT
STILL REMAINS TIGHT FOR GUSTY WEST TO SOUTHWEST WINDS UP TO 50 MPH
FOR THE INTERSTATE 80 WIND CORRIDORS THROUGH AT LEAST MIDDAY.

ON THE RECENT ZONE FORECAST UPDATE...INCREASED CLOUD COVER...
LOWERED MAX TEMPS A FEW DEGREES AND TWEAKED WINDS.

PREV DISCUSSION... /ISSUED 314 AM MST TUE FEB 5 2013/ 

SHORT TERM...TODAY THROUGH THURSDAY NIGHT...

WIND GUSTS ACROSS THE WIND PRONE AREAS OF ARLINGTON AND BORDEAUX
HAVE GENERALLY DROPPED BELOW 50 MPH OVER THE PAST FEW HOURS. THIS
IS IN RESPONSE TO A GRADUALLY WEAKENING LLVL GRADIENT BEHIND THE
SHORTWAVE CURRENTLY MOVING ACROSS THE DAKOTAS. CANCELLED THE HIGH
WIND WARNING EARLIER AS THE 700MB CAG-CPR GRADIENT DROPS TO AROUND
40 METERS BY 12Z (DOWN FROM 55 METERS THIS PAST EVENING). STILL
THINK THERE COULD BE A FEW GUSTS TO AROUND 50 MPH NEAR ARLINGTON
THROUGH THE MORNING AS THE GFS SHOWS WESTERLY 700MB WINDS AT 45
KT AND A FAVORABLE SFC PRESSURE PATTERN. SHORTWAVE RIDGE WILL
MOVE OVER THE REGION BY THIS AFTN...RESULTING IN A FEW DEGREES OF
WARMING FROM YESTERDAY. ALTHOUGH WINDS WILL BE WEAKER THAN
YESTERDAY...A DEVELOPING LEE TROUGH OVER EASTERN WYOMING BY THE
AFTN WILL MAINTAIN BREEZY-TO-LOCALLY WINDY CONDITIONS ACROSS
SOUTHEAST WYOMING.

STORM SYSTEM CURRENTLY SEEN ON WATER VAPOR IMAGERY OFF THE PACIFIC
NORTHWEST COAST WILL QUICKLY PROGRESS EASTWARD THROUGH TONIGHT.
THIS SYSTEM WILL BE A SHORTWAVE WITH LIMITED MOISTURE AS IT MOVES
ACROSS WYOMING ON WEDNESDAY. MAIN IMPACT FROM THIS SHORTWAVE WILL
BE TO INCREASE THE FLOW ALOFT AND LLVL GRADIENT SLIGHTLY...ALTHOUGH
THE 700MB CAG-CPR GRADIENT REMAINS ONLY AROUND 35 METERS DURING
ITS PASSAGE. WHILE THERE WILL LIKELY BE A FEW GUSTS TO 50 MPH LATE
TUESDAY NIGHT THROUGH MIDDAY WEDNESDAY ACROSS THE GAP AREAS...THE
MARGINAL LLVL GRADIENT AND POSITION OF THE UPPER LEVEL JET
(SOUTHEAST WYOMING IS IN THE RIGHT ENTRANCE REGION) DISCOURAGE A
WIDESPREAD HIGH WIND EVENT. THE SHORTWAVE IS STRONG ENOUGH TO
FORCE A COLD FRONT ACROSS THE CWA BY WEDNESDAY AFTN...SO EXPECT A
BIT OF COOLING FROM TODAY'S TEMPS. WITH LIMITED 700-500MB MOISTURE
AND DYNAMICS...ONLY HAVE A SLIGHT CHANCE OF SNOW OVER THE SIERRA
MADRE/SNOWY RANGES ON WEDNESDAY WITH THE SHORTWAVE TROUGH PASSAGE.
QUIET WEATHER WILL OCCUR FOR THE REMAINDER OF THE SHORT TERM.
INCREASING SOUTHWESTERLY MID LEVEL FLOW WILL OVERSPREAD THE CWA BY
THURSDAY NIGHT IN ADVANCE OF THE LARGE SCALE TROUGH DIGGING INTO
THE GREAT BASIN.

LONG TERM...FRIDAY THROUGH TUESDAY

STILL SOME DIFFERENCES BETWEEN THE GFS AND ECMWF ON UPCOMING
STORM SYSTEM FOR THE WEEKEND. GFS CONTINUES TO BE SLOWER AND
FURTHER SOUTH WITH THE UPPER LOW. IT IS HOWEVER...IS BEGINNING TO
SHOW SIGNIFICANT QPF OVER NORTHEASTERN COLORADO AND SOUTHERN
PANHANDLE. GIVEN THE CONSISTENCY OF THE ECMWF IN ITS SOLUTION...I
FOLLOWED ITS GUIDANCE MORE CLOSELY.

BY FRIDAY AFTERNOON...THE UPPER LOW FROM THE ECMWF IS LOCATED OVER
WEST CENTRAL UTAH. GREAT UPPER LEVEL DIFFLUENCE AS SOUTH CENTRAL
WYOMING LOCATED NORTHEAST OF THE LOW. CWFA IN FAVORABLE LEFT FRONT
QUADRANT OF A 90KT JET LOCATED OVER NORTHERN COLORADO FRIDAY NIGHT
INTO SATURDAY MORNING. SNOW INITIALLY DEVELOPING OVER CARBON
COUNTY FRIDAY EVENING...SPREADING SLOWLY EASTWARD SATURDAY.

BY SATURDAY NIGHT/SUNDAY MORNING...THIS IS WHEN AREAS EAST OF THE
LARAMIE RANGE WILL BEGIN TO SEE WIDESPREAD SNOW. IMPRESSIVE QPF
FORECAST FROM 06Z SUNDAY THROUGH MUCH OF THE DAY. SHOULD WE
REALIZE THE ECMWF QPF TOTALS...WE ARE LOOKING AT CLOSE TO .7
INCHES OF LIQUID THROUGH 00Z MONDAY ACROSS THE SOUTHERN PANHANDLE.
WITH 700MB TEMPERATURES OF -10 TO -12C...ALL OF THIS MOISTURE WILL
FALL AS SNOW. JUST OFF TO THE SOUTHEAST OF THE CWFA...THE ECMWF
SHOWING WELL OVER AN INCH OF QPF. 850MB WINDS IN THE PANHANDLE
FORECAST AT 35 TO 40 KT AS WELL...SO WE COULD SEE WIDESPREAD
BLOWING AND DRIFTING SNOW AS WELL.

LOW FINALLY EXITS EAST SUNDAY AFTERNOON WITH SNOW ENDING IN THE
PANHANDLE SUNDAY EVENING. STAY UNDER CYCLONIC UPPER FLOW THROUGH
MONDAY MORNING AS ANOTHER PIECE OF ENERGY ROTATES AROUND THE
BACKSIDE OF THE LOW EAST OF THE LARAMIE RANGE. WOULD THINK WE
COULD SEE SOME LINGERING SNOW SHOWERS DURING THIS TIME.

FIRE WEATHER...

WINDS WILL BE WEAKER TODAY THAN YESTERDAY...BUT STILL BREEZY
ACROSS SOUTHEAST WYOMING. THE SURFACE PRESSURE GRADIENT WILL
STRENGTHEN BY TUESDAY NIGHT AND WEDNESDAY MORNING...WITH WINDY
CONDITIONS RETURNING TO THE WIND PRONE AREAS OF SOUTHEAST WYOMING
WHERE GUSTS TO 45-50 MPH WILL BE POSSIBLE. TEMPERATURES WILL BE
AROUND 10 DEGREES ABOVE NORMAL THROUGH THURSDAY. MINIMUM HUMIDITIES
WILL DROP INTO THE 20-30 PERCENT RANGE ACROSS MOST OF THE PLAINS EACH
AFTERNOON THROUGH THURSDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.

&&

$$

UPDATE...JAMSKI
SHORT TERM/FIRE WEATHER...FINCH 
LONG TERM...CLAYCOMB 
AVIATION...RJM