Category Archives: 2016 05 Forecasts

My May 2016 Forecast Archive

050416 Forecast

My Forecast For Today ( May 3-5 )

Very cold air aloft will support the development of numerous showers & thunderstorms, especially from late Tuesday into Thursday.  Many will be capable of producing hail.  As cold air deepens some snow and sleet will become possible by Wednesday Night into Thursday, especially across upper elevations.

*Some accumulation of snow-sleet will be possible above 3500 feet into Thursday Morning as unseasonably cold air, and wind chills, impacts the mountain region.  Some mix of wintry precipitation will be possible at lower-middle elevations.

Overnight Into Tuesday Morning

A chance of rain showers.  Areas of dense fog at highest elevations and in places that had heavy Monday rainfall.  Winds shifting WNW-NW at 5-15 mph along middle-upper elevation mountain ridges into morning.  Temperatures dropping into the 40s to middle-upper 50s ( coolest along highest mountain ridges ).

Tuesday Afternoon

Mostly cloudy.  Cooler.  A chance of showers.  Local thunder possible.  WNW-NW winds at 5-10 mph, with higher gusts.  Temps varying from upper 40s to lower 50s at highest elevations to the middle to upper 60s.

Tuesday Night Into Wednesday Morning

Mostly cloudy.  Chilly.  A chance of showers.  Local thunder & small hail possible.  W-NW winds generally less than 10 mph below 2700 feet.  W-NW winds 5-15 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures varying from upper 30s to lower 40s at highest elevations to the mid 40s to around 50 degrees.

Wednesday Afternoon

Partly to mostly cloudy.  A chance of showers and hail producing thunderstorms.  SW-W winds at 5-15 mph, with higher gusts.  Temperatures varying from the 40s to lower 50s at highest elevations to the middle-upper 60s ( warmest at lower elevations and south toward the Tri-Cities ).

Wednesday Night Into Thursday Morning

A chance of showers and hail producing thunderstorms during the evening.  Rain showers becoming mixed with and changing to snow-sleet overnight into morning in the upper elevations ( mixed precipitation possible in middle to lower elevations ).  WNW-NW winds 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges-plateaus.  Temperatures varying from upper 20s to lower 30s at the highest elevations in the High Knob Massif to the upper 30s to lower 40s.  Wind chills in the 20s and 30s along mountain ridges, with 10s in gusts on the highest peaks ( some rime formation possible along the highest ridges-peaks ).

 

Weather Discussion ( May 2-5 )

The stormy weather pattern that has opened May will be continuing through coming days, with forces driving this storminess shifting toward instability based cold air aloft.

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

Increasingly cold air aloft will begin to deepen in the vertical during coming days, with a large lapse rate or difference between surface layers and altitudes above 15,000 feet within the atmosphere, where air temps will plunge to -10 to -20 degrees ( Fahrenheit ) below zero.

European Model 500 MB Height Anomaly Forecast
European Model 500 MB Height Anomaly Forecast – 8 AM Wednesday ( May 4 )

This pattern is simply straight out of winter, with only modification by the time of year ( e.g., high May sun angles, longer days, warmer ground temperatures and low-level moisture via evaporation and transpiration ) working to ease some of the pain of a late season cold blast.

European Model 500 MB Height Anomaly Forecast
European Model 500 MB Height Anomaly Forecast – 8 AM Thursday ( May 5 )

During May a setting analogous to the heart of winter creates other complicating factors, namely it enhances instability driven by increasingly cold air aloft and lapse rates ( differences in temperature between surface layers and altitudes above 10,000 to 20,000 feet in the free air ).

Numerous showers and thunderstorms will become possible as this instability increases, with many being capable of producing hail as the freezing level aloft drops.  Past settings like this have occasionally generated copious amounts of small to medium size hail.  A spring example being April 15 in 1998 when VDOT snow plows had to be called out for 3-4″ hail depths on routes such as U.S. 23 and State Route 80.
Pink Lady's-slipper Orchid ( Cypripedium acaule )
Pink Lady’s-slipper Orchid ( Cypripedium acaule ) – May 1, 2016

At a time of year when gorgeous spring ephemeral wildflowers are part of the main show, such a late season blast of cold air might seem unheard of; however, it is actually rather common ( and over the long-term locally gave rise to a May 10 spring planting rule…not to plant tender vegetation prior to this time due to cold air ).

At times the cold air blasts can be substantial enough to support snow, with May falls of snow recently being documented during May 1989 ( 2-4″+ ) and May 1992 ( 2″ up to 2-3 feet ).  May snow flakes being most recently observed during May 2005.

 It is too early to know what night or nights will be most favorable for valley frost, but an early estimate would be following the break-down of the northerly-northwest low-level flow into the upslope side of the mountains by late Thursday into Friday morning.  Stay tuned for updates.

050216 Forecast

My Updated Forecast ( April 30-May 3 )

ALERT For Heavy Rainfall With Strong To Severe Thunderstorms Monday Afternoon Into Monday Night

SPC Severe Thunderstorm Watch
SPC Severe Thunderstorm Watch

*The Storm Prediction Center Has Issued A Severe Thunderstorm Watch Effective Until 10:00 PM Monday

In addition, due to heavy weekend rains the threat for rapid rises along streams and flooding of low lying, poor drainage locations needs to be respected.  Please turn around, don’t drown if encountering a water covered roadway.

 

Saturday Afternoon

Cloudy & cool with light rain & drizzle.  Thunder possible, especially south to southeast of the High Knob Massif and Tennessee Valley Divide.  Northerly winds 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges and plateaus.  Temps in the 50s to mid 60s along and north of the High Knob Massif-Tennessee Valley Divide, with 70s to lower 80s to the south and southeast.

Saturday Night Into Sunday Morning

Showers & thunderstorms becoming likely.  Some storms may be strong.  Downpours possible.  Winds becoming SSE to SSW at 5 to 15 mph, with higher gusts, below 2700 feet.  Winds SSW to SW at 10 to 20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures mainly in the 50s and 60s ( coolest at highest elevations ).

Sunday Afternoon

A chance of hit-miss showers & thunderstorms.  Winds SSW-SW at 5-15 mph, with higher gusts.  Temperatures varying from 60s across upper elevations to the 70s to around 80 degrees ( warmest at lower elevations ).

Sunday Night Into Monday

A chance of showers.  Thunder possible.  Winds SSW to SW at 5-15 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet.  Winds SW-WSW 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps in the 50s to lower 60s.

Monday Afternoon

Mild & humid with showers & thunderstorms developing.  Some storms may be strong to severe with torrential rain and strong winds-hail.  Winds SSW to SW 5-10 mph, with higher gusts.  Temperatures varying from the 60s across upper elevations to the mid-upper 70s in lower elevations.

Monday Night Into Tuesday Morning

Showers & thunderstorms.  Rainfall may be heavy at times.  Thunderstorms may be strong to severe during the evening.  Winds shifting WNW-NNW at 5-15 mph into the overnight and morning.  Temperatures dropping into the 40s to mid-upper 50s ( coolest along high mountain crestlines ).

 

Weather Discussion ( April 30-May 3 )

An update on this Monday ( May 2 ) is for the threat of strong-severe thunderstorm development and heavy rainfall, especially for counties along and west of the Virginia-Kentucky stateline & Cumberland Mountains.

JKL Doppler Radar
JKL Doppler Radar At 3:06 PM Monday – May 2, 2016
Rainfall totals reached 1.00″ to 2.00″ in many places along the Virginia-Kentucky border during the weekend, with training storms having already developed over the foothills of eastern Kentucky on this Monday afternoon.  An eastward propagation during the afternoon will need to be closely followed.
Brief showers already observed Monday in Clintwood have been pounding with large drops and fast fall rates ( often a signal that the atmosphere is primed for torrential rainfall production ).
Cloud Towers Billow In Advance Of Severe Thunderstorm
Dark Cloud Towers Billow In Advance Of Severe Thunderstorm – May 1, 2016
Severe thunderstorms just brushed the Clintwood area late Sunday, with Summer Salyers reporting dime size hail and moderate rainfall north of town in the Skeetrock community.  Very large hail fell along portions of Pine Mountain into the Hurley area of Buchanan County.

Rainfall Totals Observed May 1 to 9:00 AM on May 2

Clintwood 1 W: 1.35″
( 3.48″ since April 1 )

Upper Norton Reservoir: 1.33″
( 6.69″ since April 1 )

City of Norton Water Plant: 1.15″
( 4.17″ since April 1 )

Coeburn Water Treatment Plant: 1.12″
( 4.69″ since April 1 )

The month of April was atypically dry.  During only 24-36 hours, rainfall at the beginning of May was 63% as much in Clintwood, one of the drier locations, as observed during all of April.

An update on this Saturday is to account for a northerly wind shift into the Cumberland Mountains that has kept temperatures in the 50s ( highest elevations ) and 60s to generate a large north-south difference across the region.

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise
Saturday PM temperatures reached 80 degrees or higher in parts of the Tennessee Valley verses only 50s above 3000 feet across the High Knob Massif, with low-mid 60s in Norton-Wise & Clintwood amid development of light rain and drizzle.
NASA Visible Image At 4:30 PM
NASA Visible Image At 4:30 PM Saturday – April 30, 2016

The best chance for any thunder through the remainder of this afternoon will be south & southeast of the Cumberland Mountains, before a wind shift back toward the SSE-SSW will allow more unstable air to come northward tonight into Sunday.

Storm Prediction Center
Storm Prediction Center Risk Regions – Today & Tonight
The Storm Prediction Center maintains a marginal risk for severe thunderstorm development through Sunday.
Storm Prediction Center
Storm Prediction Center Risk Regions – Sunday

The strongest storms this afternoon remain far to the south over the Dixie States and Gulf Coast.

Regional Doppler Composite At 4:08 PM Saturday - April 30, 2016
Regional Doppler Composite At 4:08 PM Saturday – April 30, 2016

Forecast model runs today are cranking out heavy rainfall amounts, but timing and placement of heaviest rains does remain in question.

NAM 12 KM Model Total Rainfall Forecast
NAM 12 KM Model Total Rainfall Forecast To 8 PM Tuesday – May 3, 2016

The NAM Model group is forecasting the heaviest rains to develop tonight into Sunday morning.

NAM 4 KM Model Total Rainfall Forecast
NAM 4 KM Model Total Rainfall Forecast To 8 PM Monday – May 2, 2016

The Saturday AM run of the European Model is most bullish with a surge of heavy rain and storms by late Monday into Tuesday, with the GFS Model somewhat in the middle but generally closer to the NAM with heaviest amounts being predicted for tonight into Sunday.

GFS Model Total Rainfall Forecast
GFS Model Total Rainfall Forecast To 8 PM Monday – May 2, 2016

The RLX NWSFO ( Charleston, WV ) has issued a Flood Watch for most of their coverage area through Sunday.

GFS Model
GFS Model Total Rainfall Forecast To 8 PM Tuesday – May 2, 2016

Clearly, models are showing the potential for heavy rainfall but timing and placement differences are raising questions as to when and where this will occur.  This continues to be one of the driest spring’s on record, which also remains a factor in any heavy rain forecasts.

Stay tuned to NOAA Weather Radio for any additional watches and/or warnings that may be needed through the next few days.