Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 kcys 200548 

Area forecast discussion
National Weather Service Cheyenne Wyoming
1048 PM MST Tue Nov 19 2019

Short term...(this evening through Thursday night)
issued at 230 PM MST Tue Nov 19 2019

Forecast concerns deal with timing on snow Wednesday...along with
snow amounts across our western County Warning Area.

Currently...cold front moving into northwestern Wyoming this
afternoon as the northern low splits. Northern energy from the
split shortwave moving into central Montana this afternoon is
driving the front south southeast. Across southeast Wyoming...we
are seeing scattered to broken mid and upper level clouds. It is
fairly warm outside with 2 PM temperatures in the upper 50s and
low 60s. From latest water vapor imagery...upper ridge axis
overhead at this time. To our southwest across the Desert appears the southern low is now beginning to open
up with widespread showers and thunderstorms developing over
southern Arizona.

We look to be on track for a fairly widespread snow event
Wednesday. Models appear to be in good agreement on timing. Quantitative precipitation forecast-
wise...NAM seems to be really bullish Wednesday across Carbon
County. It is showing 6 hour qpfs around .63 inches from 18 to 00z
Wednesday while the GFS and European model (ecmwf) showing around .25 inches for
the same timeframe.

Two waves of energy with this system. First comes in tomorrow
morning with the southern shortwave remnants. European model (ecmwf) moves this
through into the Nebraska/Kansas area by 00-03z Thursday. May see
a brief decrease in snow amounts after that time...but then the
northern closed low tracks into Utah and northern Arizona late
Wednesday night. We will be under upper level difluence for
Thursday morning for another fairly widespread snow. Not enough
time to split the two events in my decided to keep it
all one event running from 18z Wednesday to 18z Thursday. Went
ahead and upgraded watches to warnings across Carbon County as we
are in the timeframe to have these warnings out.

Snow ends Thursday afternoon from north to south. Right now...feel
impacting snow will end by 18z...but later shifts may need to
extend the warning into the afternoon.

Later shifts are going to need to evaluate areas east of our
current headlines for expansion of advisories east. Could see this
evening or overnight shift adding the Laramie range and possibly
some of our southeast Wyoming plains zones into an advisory.R

Long term...(friday through tuesday)
issued at 230 PM MST Tue Nov 19 2019

Friday through Sunday looking to be pretty quiet across the County Warning Area
as an upper ridge axis passes across Friday and leaves nwly flow
aloft behind it over the weekend. Temps will moderate Friday and
Saturday and stay mild for Sunday. Next upper trough approaches
on Monday along with the next cold front and should bring some
snow showers to much of the area later Monday and Monday night.
Chilly Tuesday with isolated snow showers still possible.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1042 PM MST Tue Nov 19 2019

VFR conditions at all area terminals at this hour, however
deteriorating flight conditions down to IFR/LIFR can be expected
to begin in the next 6-18 hours as our next winter system
approaches. Snow, reduced visibility, lowered ceilings, and gusty
winds can expected at most terminals starting as early as
Wednesday morning near krwl and eventually making its way into the
NE Panhandle by late afternoon Wednesday. Recent model guidance
has slightly slowed down the onset of restricting flight
conditions since the 00z taf issuance so adjusted the 06z tafs


Fire weather...
issued at 230 PM MST Tue Nov 19 2019
minimal fire weather concerns over the next 48 to 72 hours as a
low pressure system from the southwestern U.S. Moves northeast
into northern Colorado. This low will bring widespread
accumulating snow to southeast Wyoming and Nebraska Panhandle
beginning early Wednesday morning. Snow expected to be widespread
Wednesday afternoon and evening and will continue into Thursday
morning. Southern areas...the I-80 corridor could see snow
continuing into Friday morning.


Cys watches/warnings/advisories...
Wyoming...Winter Weather Advisory from 11 am Wednesday to 11 am MST
Thursday for wyz101-103-113>115.

Winter Storm Warning from 11 am Wednesday to 11 am MST Thursday
for wyz104-105-109-110-112.

Winter Weather Advisory from 5 am Wednesday to 11 am MST
Thursday for wyz111.



National Weather Service Glossary of Abbreviations